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Why does NaCl react differently with a boiled potato and with a raw one
Well my question is based on this question down below.

For those who don't speak german:
You have two potato slices one of them is boiled the other one is just raw.
Now you scatter some salt over both surfaces of the two different slices and wait about one hour.
After the time is over the salt on one potato isn't in his crystalline formation anymore.
So my question is why are behaving both slices different?

My guess is that the carbohydrates ( Starch ) reposition and the starchcores bind with H2O.
So the H2O binds with the NaCl?

I would really enjoy it when somebody could tell me the chemical reasons why this happens.

"After the time is over the salt on one potato isn't in his crystalline formation anymore." But on which one potato the salt will remain crystalline and which one not? (however I'll perform the experiment tomorrow because today I'm going to sleep); but what should be the expected-specification according to your reference?

As well; to my experience; ample water comes out if I add salt to raw  cut-potato before I fry them. But not that way from boiled potato. However if a boiled potato is crushed then again it become soft and moisty; and remain the moistness (doesnot stiffen like a starch gel).

I think it should be in Chemistry stack exchange instead of biology.

I've done the experiment today. Non boiled potato dissolved the large portion of salt within 30 to 45 min. whereas boiled potato just moistened the salt, but not dissolved that way. @SanjuktaGhosh I think this is due to osmosis through cell-membrane whereas boiled potato there should absence of that event due to denaturation of cell membrane. I think this question is appropriate to biology SE.

@AlwaysConfused seems far more likely to me that the boiled potato simply doesn't have enough water to melt the salt.

Maybe this passage is referring to this experiment?
The key missing from your description is that each potato is placed in water. When the cells are intact (unboiled), this causes water to flow into and out of the cells via osmosis: into the cells from the tray of water, and out from the cells into the salt. Once the cells are destroyed via boiling, there are no intact membranes to cross to osmosis does not occur and the salt remains undisturbed.

Maybe OP is telling about watery content coming out from cut surface of raw potato but not from boiled potato. But OP is not clear enough about on which-one potatoe the're expecting the dissollution of salt?

Well sorry if I'm confusing you but I guess you're always confused:P
For those who are saying I forgot about the point that the potatoes were placed in water before the salt was scattered. Well that is exactly the problem just one were placed in water and got boiled. The other one was never getting in touch with water. And I don't know if it's the raw or boiled one which changes the crystalline formation.
The answer that the boiling destroys the cells and also the membranes which are essentially needed for the osmosis causes the behavior that the boiled let the salt untouched seems legit.

@RonySchmied No I didn't used that added-water outside the potato. But still I got the same result as that youtube link provided by BryanKrause.... raw potato dissolved the salt but boiled (and cooled to room-temp) potato could not dissolve the salt... it just moisten the salt slightly.


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Does plasmolysis kill plant cells?
I know when a plant cell becomes fully plasmolysed that the protoplast shrinks away and eventually is no longer joined to the cell wall.
Is this irrevocable damage? Can the cells survive it and continue to function if they are put back into a favourable solution.
If so how does the protoplast rejoin to the cell wall?

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No. Cell-plasmolysis is not necessarily fatal for the cell. Plant cells normally recover from this condition when water is available. (But cell death can take place in excessive or prolonged lack of water).
It is an incomplete truth that during plasmolysis, plant cells get detached from the cell wall. Actually the plasmodesmatal connections remain there and a portion of the cortical (outermost)-layer of cytoplasm, mainly containing "cortical endoplasmic reticulum", a group of endoplasmic reticulum spanning close to the cell wall; remains there.
Now, when plasmolysis take place, the cell-membrane shifts apart from the cell wall; but at the place in-between, there forms fine cytoplasmic threads called Hechtian strands. So the connection is retained. (As well at some portion of cell-wall, the bulk protoplast remain touched there)
Here are photos showing hechtian strand; taken from the book Plant Cell Biology- structure and function, by Gunning and Steer, Jones and Bartlett publishers, Copyright 1996;

Image-1 (Book image 16-C)

Hechtian strands of stretched plasma membrane extended from the plasmolysed protoplast to the cell wall (K. Hecht , 1912, was the first to  study them in detail). This confocal micrograph shows strands in a 16 μm- deep zone. Some strands extend from plasmodesmata (arrows), where the membrane passes through the cell wall, butmany attached to other sites. in 1931 another early investigator J. Plowe, pushed plasmolysed protoplast along inside their cell walls, observing that existing strands stretched and broke, and that new strands could form. In today's terminology we would say that new strands arise when freebinding sites on the plasma membrane contact and bind their ligands in the cell wall.

Reference:

Plant Cell Biology- structure and function, by Gunning and Steer, Jones and Bartlett publishers, Copyright 1996

Update: An interesting information; there is one method of plant protoplast isolation without enzymic digestion of wall; which uses plasmolysis. Since the protoplast(and cell membrane) get shifted from part of cell wall; it becomes easy to rupture the wall without rupturing the cell-membrane. (Discussed in this website). The protoplast remains alive after plasmolysis otherwise we won't be able to use this method for protoplast culture, cell fusion etc.

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Does Methanol cause similar intoxication as Ethanol?
Take two average healthy adult males weighing 80 kg. Neither has, ahem, developed their alcohol tolerance to any significant degree.
One imbibes 1 shot, 40 ml of 40% Methanol, and another 40 ml of 40% Ethanol (vodka) to empty stomach.
Now the vodka drinker should feel the drink going to their head, and he'd become just slightly drunk, and that's about it. No hangover expected from 1 shot of vodka, either.
What would be the effects on the Methanol drinker? Info on other effects would be nice too, but most importantly, would he become drunk, and how much compared to the vodka drinker?
If 16 ml of absolute methanol seems so much, that other toxic effects will dominate over "feeling drunk", then you can consider a smaller amount. The crux of the question is, does Methanol cause one to "become drunk" same way as Ethanol.

WARNING, just in case, to offset the casual tone of above question: Never drink anything which even just might contain Methanol! It's an easy way to die, or just go blind if you're "lucky"! It is not a useful way to get drunk or high, ever.

According to Wikipedia the density of methanol is 0,79 g/ml. Your 40ml of 40% Methanol contain about 16ml pure methanol which translate into 12,6gr. According to this paper the toxic dose starts around drinking 8g, so you would have some other, severe problems.

@Chris Yes, I'd expect so. I tried to choose an amount, which should feel like going to ones head (1 shot of vodka to empty stomach), yet shouldn't be lethal amount of Methanol.

A starting point could be this review which states  :   "With respect to GABAA receptors, a number of alcohols [...], including methanol, [...] potentiate GABA-gated current. The potencies of these alcohols tend to increase with chain length.". Not a definitive answer, though, because this is mole-for-mole at the receptor site, only for GABAaR, and does not take into account kinetics of absorption/passage of the BBB.

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Competition in DNA hybridization to RNA
After we separate the two DNA strands, what makes one of the two strands combine with the labelled mRNA strand instead of the old complementary strand?

You usually add your labelled probe in a large excess to avoid this.

Like chris said it is only a question of Ratio, some will recombine with their complementary strand, but a lot more with the mRNA.

Then why don't you guys write an answer? Comments are NOT for answers. It says so when you open the comment box.

@David Because I had no time to write up a proper answer. One line is not an answer.

Yup, same here. I really dislike not having references in the biology SE. I guess for this type of question it is ok.

In this type of experiment the concentration of the mRNA will be greater than the concentration of the starting DNA.
When the DNA strands separate, the DNA and mRNA will be in competition for the complementary strand. Using really high concentrations of mRNA compared to the DNA will give it advantage to recombine with a higher frequency and give a higher ratio of the DNA-mRNA combination.
It is all a question of ratio.


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Origin of the biochemical term, Pi (inorganic phosphate)
I would like to know when the term Pi (inorganic phosphate) was introduced in the representation of biochemical reactions, how it was originally defined, and the justification given then for using it rather than an individual species of phosphate.
(I would also be interested in the current justification, but that’s probably another question.)
Let me provide some background to my question. Phosphoric acid (H3PO4) has three ionizations, which produce successively the species: dihydrogen phosphate (H2PO4–), monohydrogen phosphate (HPO42–) and orthophosphate (PO43–). At pH 7.4, according to the Wikipedia entry on phosphate, the main species are the mono- and di-hydrogen phosphates (61% and 39% respectively). The term Pi must have been introduced in the 1950s at latest (perhaps before the war), at a time when there would have been little knowledge of the nature of the species involved in reactions involving phosphate — certainly not at the active sites of enzymes.
One of the reasons I am curious to know how the term was introduced is the extent to which it persists in 21st century biochemical text books, where it would seem that many authors either do not know or do not care to explain to their readers why they are still using it at a time when much more is known about the reaction mechanisms. Neither of two well-known texts explain the different ionizations of phosphate, and give only parenthetical definitions in terms of a single species — different in each case: Berg et al. referred to Pi as orthophosphate, whereas Nelson and Cox’s, Lehninger  Principles of Biochemistry referred to it as HPO42–.
Acknowledgement: This question was provoked by the SE-Biology question — Where is the H+ ion in this step of glycolysis coming from?

may be it is a gross stoichiometric term. A similar situation exists; where many school and college biology-textbooks write TCA cycle as 'citric acid', 'isocitric acid' etc (and accordingly sometimes draw structures as non-ionized acid groups). But all international books use terms like "citrate", "isocitrate", etc. and only draw their anionic forms. Thanks nice question.

May be because Pi lacks carbon (i.e. unlike ATP or GTP etc), so,  called-as ''inorganic". However pyrophosphate or PP is also biologically important but it is not termed as Pi or inorganic phosphate

I think the umbrella term "inorganic phosphate" (Pi) was introduced as a shorthand for "phosphate dissolved in water", precisely because phosphate exists as both HPO4 and H2PO4 forms, as you mention --- it would be inaccurate to use only one formula, and it's inconvenient to have to use both. A similar shorthand is CO2(aq). It may be inaccurate for detailed enzymatic mechanisms, but it's sufficient for describing overall enzymatic reactions in water, and I would guess this is why it's still used. This is just my guess, haven't looking into this in depth ...

@Roland — I had started to do some historic back-tracking when nobody answered, but only got so far. I need to recall old books from the stack of my University library in order to get at the sources and have delayed until I have more time and energy. I'll post an answer to my own question eventually.

I'm voting to close this question as off-topic because  it would be a better fit for history of science and mathematics (hsm.SE)

I thank the person who corrected my spelling of "referred" but have reverted his other gratuitous and unjustified alterations. "When" was italicized for emphasis. It is not unreasonable to do so.  As for the question of whether the full stop (period) in a sentence is inside or outside the parentheses, that is a matter of style. My style is that of The Penguin Handbook — see the accepted answer to a question on SE English Language & Usage. Noli me tangere.

This terminology is at least as old as September 1944 when Enzymatic Synthesis of Acetyl Phosphate Journal of Biological Chemistry
155,  55-70 was published by Lipmann, which says:

Inorganic phosphate, referred to as Pi, was estimated
colorimetrically

See also the definition of "inorganic phosphate" and "orthophosphate" from this 1943 University of Wisconsin Thesis:

Compound:  Inorganic phosphate or orthophosphate
Definition: Phosphate whose calcium salt is insoluble in water-alcohol mixtures under the conditions to be described. E.G. NaH2PO4

In other words, "orthophosphate" was a generic term for mono, di, or tri basic phosphate.  It did not have the narrower meaning attributed in the OP.

Thank you for this piece of information which suggests an answer to the origin of the abbreviation, Pi, for inorganic phosphate. However it is interesting that in this paper Lilpmann does not use Pi in the biochemical equations he presents, but instead uses H.OPO3H2 (i.e H3PO4 — undissociated phosphoric acid). So I suspect that Pi was first used in equations subsequently, perhaps by Lipmann himself. Unless someone does it for me, I'll start to follow this up.

@David ok, start with equations 4 and 6 in this 1953 article: http://www.jbc.org/content/203/1/501.short

How do you find them? That's very interesting because in the list of abbreviations it defines Pi as orthophosphate, which is chemically precise, but ionically incorrect. However this is disguised (as it was for years) by the fact that the equations are "biochemical equations" and do not involve chemical formulae. I'll poke around a little next week in the hope that a comprehensive answer can be constructed.

@David I just searched in Google scholar http://scholar.google.com/ for terms like "inorganic phosphate" and "pi", or "orthophosphate" and "pi".

@David "orthophosphate" was a generic term for PO4---, HPO4--, or H2PO4- .  I clarified this in the answer.

Aaaah. According to the Wikipedia article (which I don't necessarily trust) orthophosphate currently refers to the triply negatively-charged ion, as in the question. I see you are a longstanding contributor to the Chemistry list. Is there a current chemical consensus on the term?

@David I think Wikipedia is just wrong about this and "orthophosphate" is a generic term for phosphoric acid and any salt thereof, but in contrast to metaphosphate, pyrophosphate, and polyphosphate.  "Orthophosphate" has been used in this generic way for at least 150 years.

OK. You get the money. I'll try to do a little more on this and perhaps post a summary.


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Performing PCR on samples whose DNA concentration is nul
Is it vain to perform a PCR on samples whose DNA concentration was measured as nul by a NanoDrop?

Nope, you could get amplification from samples that are orders of magnitude below the nanodrop detection limit (~2 ng/uL). To compare: most manuals for polymerases recommend 1 ng of plasmid template, and will probably work with much less, especially if you use a few more cycles.
But if you expected to see something on the nanodrop, and you get nothing, something else might be completely wrong.

You can go down into the picogram range. And you could use nested PCR to ensure specificity.

Some times nanodrop is unreliable. However, to be sure that you are not wasting your time, I would redo the extraction. Nanodrop in a lot of PCR methods is a control test to validate that the extraction went well. So, I would redo the extraction if I where you.


text:
Problems interpreting gram stain slide
My main question is this: when you interpret gram stain results, does the majority color determine if its pos or neg?
We've been given unknowns and now have to determine what the organism is. I'm having trouble interpreting gram staining results. As far morphology they are all cocci and (sort of) in clusters but (this is the confusing part) they are both purple and pink. I understand that purple indicates gram+ and pink is gram-, but there should be one genus of organism not two. So shouldn't there be only purple or only pink, but not both? Should I be looking for the "majority" color and using that to decide whether I have pos or neg? That is, if its mostly purple, does that mean pos, ...but if so, then why are there still pink cocci on the slide?
I also understand why gram-pos appear purple, --that the crystal violet-iodine complex is retained due to thicker cell walls in gram-pos..... and thinner cell walls in gram-neg, so they are decolorized and appear the color of the counterstain.
Also I definitely did not see any rods in my slide, just cocci.

The only reason that it shows both colors is due to imperfect manipulation while staining. You cannot count on the majority to determine the result of the stain.
In your specific case, rinsing or decoloration with EtoH was probably not done enough and safrainin wasn't completely eliminated.
The best way to be sure of the result would be to redo the coloring.
A good tip while staining is to have duplicates or triplicates.
Secondly, to answer what you said here:

I also understand why gram-pos appear purple, --that the crystal
  violet-iodine complex is retained due to thicker cell walls in
  gram-pos..... and thinner cell walls in gram-neg, so they are
  decolorized and appear the color of the counterstain.

Actually it is not only the thickness of the cell wall that will cause the bacteria to retain or not the crystal-violet. Gram positive bacteria have a plasma membrane then peptidoglycan on top while Gram negative bacteria have a plasma membrane, then peptidoglycan and another outer membrane on top. Crystal violet "sticks" primarily to the peptidoglycan.
Decoloring will remove the stain on the outer membrane of gram negative bacteria. You were right with the fact that Gram positive bacteria will have thicker peptidoglycan.
Gram + vs Gram - cell walls http://www.diffen.com/difference/Gram-negative_Bacteria_vs_Gram-positive_Bacteria

I did 15 seconds of EtoH rinse but I'm hoping I can just do whole test again because it should be all purple , but its not gram neutral its definitely one microorganism


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Could all mammalian receptors be described as allosteric?
Allosteric regulation in enzymes is where a molecule binds at a site other than the active site and thus changes the tertiary structure of the active site, hence altering the binding of substrate and formation of enzyme-substrate complexes.
As I understand it, if this is extended to receptors, for example G protein-coupled receptors, which effectively causes a conformation change which is transmitted across the membrane and 'activates' a G protein which is associated with the receptor. The Gα subunit swaps a GDP for a GTP which causes the dissociation of the alpha from the beta-gamma coupled subunits and from the receptor. The dissociated Gα and Gβγ subunits then take part in a cascade process interacting with other molecules.
However, photoreceptors such as rods/cones in the eye respond to light. These photons tend to cause changes in the structure of the rhodopsin/iodopsin pigments and not the actual 'receptors' themselves. G proteins do seem to be involved in this process too.
Therefore, are photoreceptors allosteric? And if not, are they an anomaly in mammalian receptors, or are there many other examples of receptors that do not rely on allostery?

Signaling 'receptors' are not necessarily enzymes; 'receptor-proteins' is a different  functional-class of protein. But yes all they work in lock and key mechanism. I can assume fro where this confusion arise. Older biochemistry texts classifying protein by work (such as motor protein, carrier protein and such and such) that lists lacked receptor-proteins. Me too once had this confusion so I can understand what you're trying to say.

Not only for mammals; for all sort of signaling-receptors of universe; you could compare it with allosteric enzyme. Because just like that enzyme's 2 sites : allosteric site and active site; the signal-receptor proteins have main 2 types of sites: the 'ligand' binding site (compare it with enzyme's "allosteric" site) and the next-messenger's binding site (compare with the enzyme's "active site").

"Allosteric" refers to an alternate site of action, but it is not limited to a discussion of enzymes. For a protein that is a receptor, allosteric modulation refers to modulation of that receptor away from the binding site or "active site" of the endogenous ligand.
Although it is true that the receptor may have enzymatic activity when a ligand is bound, it would be non-standard to use the term "allosteric" to refer to the normal ligand binding site, even if this terminology is technically correct with respect to the enzymatic activity.
There are many receptors which are not enzymes at all: a great example would be ligand-gated ion channels - all of the activity of these proteins is due to their conformational changes, and not due to any catalyzed reaction.

So would ligand-gated ion channels not be described as allosteric since they are not enzymes? Or they would because they rely upon conformational changes?

I think you have to be careful of how you attribute the word "allosteric" - in the canonical case, an enzyme itself is not allosteric - the modulation of the enzyme by some other factor that binds outside where the substrate binds is allosteric. "Allosteric" literally means "other site". I suppose you could consider ligand binding on an ion channel to be "allosterically" changing the protein structure at the pore, therefore allowing ions to pass.

I think you recognize a very important concept in biology: changes in protein function result from conformational changes. You are wanting to call this "allosteric" - you can probably twist the concepts to say that (most) proteins' conformation changes somewhere when something binds elsewhere on the protein, therefore an allosteric effect. Does that really get you any further than the initial statement that changes in protein function result from conformational changes?

To me, it makes more sense to reserve the term allosteric regulation for a) modulation of enzyme function at a site that is not the normal substrate binding site, or b) modulation of receptor function by changing efficacy, promoting or preventing ligand binding, etc, at a site that is neither the endogenous ligand binding site nor the site of enzymatic or other functional activity (e.g. an ion pore).


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Difference between going against and going down a concentration gradient
The difference between facilitated diffusion and active transport is that facilitated distribution occurs down a concentration gradient and active transport occurs against a concentration gradient. I understand that, as a result of these differences, active transport uses ATP so that it can bind to the carrier protein, however I don't know what is meant by going against a concentration gradient or down a concentration gradient.
In short, I would like to know the difference between going against and down a concentration gradient. A definition of what a concentration gradient is might clarify things a little further as well, since the definition I have doesn't help much.

"Concentration" is "how much stuff is there someplace?" "Concentration gradient" is "how much is concentration changing from point A to point B?"
Imagine a terrain where concentration is represented by height.
"Down" a concentration gradient means from high concentration to low concentration - this is the direction things would move via simple diffusion.
"Up" or "against" a concentration gradient means from low concentration to high concentration. Moving in this direction requires some sort of energy input, such as active transport using ATP, or an electrical gradient, or something else.

Moving against a concentration gradient means that the substance is moving from a low concentration to a high concentration.
Moving down (descending) a concentration gradient means that the substance is moving from high concentration area to a low concentration area.

Welcome to Biology.SE! Your answer doesn't seem to be adding anything to the already existing answer. In addition, answers are much more likely to receive a favorable response if they include supporting references (primary literature is best). ——— Please take the [tour] and then consult the help pages for additional advice on [Answer] effectively on this site and then edit your answer accordingly. Thanks!

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Identification of Sunbirds

Location: Asansol-Durgapur region, West Bengal, India
Question:
Do they belong to the same species?
Note:

I presume the bird in Pic-1 is a male  Purple-rumped sunbird (Leptocoma zeylonica).
I think the birds in Pictures : 2-5 could be non breeding male Purple sunbird (Nectarinia asiatica) because they match very much with the Wikipedia description though the bird in Pic-2 has a short tail.
Pic-4 and Pic-5 capture the same bird.

The bird in Picture-1 is  Purple-rumped sunbird (Leptocoma zeylonica) according to this decription from wikipedia:

The males have a dark maroon upperside with a blue-green crown that glistens at some angles, bright green shoulder patch and violet/purple rump patch which is generally hidden under the wings. The underparts are whitish with dark throat, maroon breast band and purple/violet patch in the throat which is visible in some angles.

The birds in Pictures 2-5 is a single species, non-breeding male of purple sunbird (Cinnyris asiaticus) according to this description:

The male is glossy metallic purplish black on the upper parts with the wings appearing dark brown. The breeding male has the underparts also of the same purplish black, but non-breeding males may show a central streak of black on yellow underparts.

References:

Wikipedia
r/whatsthisbird


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Why DNA needs histones to be packaged and ordered?
I know that histones are proteins that package and order the DNA into structural units called nucleosomes, my question is Why DNA needs histones to be packaged and ordered ? Why DNA cannot do that by itself ?

Not all organisms have histones. Prokaryotes generally don't.

Structural packing of a lot of DNA into a small space is a useful function.

The packing and ordering also facilitates mitosis/meiosis.

Packaging also controls gene expression under certain conditions.

@Galen You could probably attempt at an answer from all of your comments.

Sort of like having one of these:

instead of this:

Surely you could simply wrap DNA up in a coil, but to do it in a neat fashion that allows you to package and repackage sections as needed, it's a lot better to have some dedicated machinery.
It is also difficult to organize DNA without a supporting structure because the negative charge of the DNA polymer repels other parts of the molecule, whereas histones are rich in positive charges.
As Galen mentioned in comments, histones both pack DNA into a smaller space (human DNA from one cell would be about the height of an adult if it was all in a straight line) and contribute to gene regulation. Modifications of histones control whether the DNA around that histone can be accessed by transcription machinery and therefore whether those genes will be expressed.

The wrapping of DNA around each histone is ~1.6 rotations.

Yes, indeed I didn't mean to be literal.

Great visual analogy! :)

You might like to add the point that DNA is itself negatively charged, so it cannot pack by itself due to repulsion. Histones have positive charge (lysine and arginine rich proteins) so that they can easily hold DNA around them.

Why DNA needs histones to be packaged and ordered?

Histones counteract retroelements, and this defense against parasitic (viral) DNA is presently considered to be their original physiological role.
see: Madhani, Cell, 2013: "The Frustrated Gene: Origins of Eukaryotic Gene Expression"

Why DNA needs histones to be packaged and ordered ? Why DNA cannot do that by itself ?

Histones are not needed to package and order DNA; Another way to order DNA would be through supercoiling – which can also be done by bacteria (lacking classical histones or histone-like proteins).
see: Griswold, Nature Education, 2008, "Genome Packaging in Prokaryotes"


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Proteome patterns between treated and control cells
We did 4 experiments to compare the amount of certain proteins in treated and untreated cells. Each experiment was done separately. Because of the high cost of experiment, we were able to perform only one pair (one treated and one untreated) sample for each experiment. We want to see which proteins are differentially expressed (minimum 1.5 fold up/down).
First approach: We have compared protein levels of all 4 treated (as a group) with the 4 untreated (as a second group). There is of course variability between all experiments, because of the nature of the cells. We have a list of the proteins that are differentially expressed as a result of the treatment, however this list is not very long.
My question is (second approach): Can we compare the proteins levels pairwise for each experiment (treated vs its respective control) and make 4 corresponding lists, and then compare these four list using a statistical tool and find which proteins are consistently up- or down-regulated? DO you think that these two different approach will generate different lists of the affected proteins?

Welcome to SE Biology. Improving this question will help to attract an answer. Currently the questions are difficult to discern as they are buried amongst lots of text. A brief description of how the measurements have been made will also help. Finally, there are lots of typographical errors that should be corrected.

Can you please describe the experiments or just mention how these are different? Are the 4 controls essentially the same sample? If not then your first approach would be incorrect.

From what I understood, and thus based my answer on, the four treated and the four untreated samples are the same, but each pair of treated and untreated samples was done at different occasions.

If I understand you did a treatment to some cells and compared them with non-treated ones. Instead of running the four experiments at the same time, you did one treated and one untreated at a time. Then you did proteomics for each sample. Is the treatment the same in all four experiments?
Edit after the further comments of the OP: So, since the four treated samples are the same and the four untreated also (same conditions except from the treatment and the treatment is the same), then the way to go is as what your collaborator did.
Identification and quantification of the detected proteins is one thing and every sample of the four are replicates. Comparison between the two conditions is another thing.
The software he uses for ID can combine the same samples and already perform the statistical analysis, so the list you have now has higher credibility in terms of the proteins it includes and their levels for your cells when they are treated or not.
Using only one of your replicates, although it might give you different number of detected proteins or different amounts of each, has lower credibility, because it's only one sample out of four. In plain words, the presence or absence or the amount of a protein might be an artifact or insignificant.
What has to be clear is that the comparison between treated and untreated conditions is done after you have received the statistically correct list of detected proteins.
Thus, and in accordance to what I had said before the edit, if you take the list for each treated sample and compare them with any of the lists of the untreated ones, it will lead to conclusions that won't be as statistically significant as when you combine all treated together and all untreated together (as your colleague did). In plain words, your conclusions will have a higher chance to be wrong.
Every statistical analysis you do yourself for each sample should eventually lead to a similar consensus as your colleague got using the statistical analysis of his software.
As a sidenote, considering how many types of proteins are in a cell, now that you have a quite short list might not be a bad thing at all and you can proceed by:

Concluding that the treatment had minor effect in the proteins that you expected it would affect (if they are not present in your lists as significant different)
Trying to understand, identify and hypothesize on the role of the proteins that made it in your comparison threshold, as they have a much higher probability of being indeed different between the two conditions.

Splitting the samples in your analysis might have a point if the conditions of the experiment were not exactly the same or the treatment level is different etc. In that case you could split the samples accordingly, but that would definitely reduce your certainty level for your conclusions.

Thank you for your reply.
It was impossible to do 4 replicates at the same time. Technically impossible. Therefore, we did 4 different experiments where we treated cells and we had an untreated control.

Usually, we did proteomics for each experiment separately. Well, because we wanted to know our results ASAP. However, last time, we gave our samples - 4 pairs (i.e., 4 separate experiments of treated vs. untreated) to our collaborator who performs proteomics for us. He is doing HPLC - QqOrbitrap analyses for us.

He always did the comparison between pairs of treated vs, the corresponding untreated, but last time when we gave him our 4 sets (4 pairs) he did something different, without our consideration - he somehow compared these samples as a two groups (this his explication), and thus he cannot extract the data for separate pairs (individual experiments).

He wrote: "Fold changes are computed with all replicates and compared statistically. Extracting the data for individual replicate would decrease the ID power. Also, I would have to reprocess all the data files." When we insisted that we would like to have the list of the identified proteins that are up- or down-regulated for each experiment, he said that this is too difficult because of the way how he set up the software for this analyses, and that will take several months.

My concern is that the "cumulative" list of the proteins that we have now because of this unexpected way of the performed analysis (two groups vs. 4 sets of treated and untreated) is much shorter. I am wondering if we perform the 4 pairwise proteomic comparisons and then will apply statistical tools  - can we expect a much longer list of the identified affected proteins or no? Thank you for sharing with me your expert opinion.

The comparison is a different step to the identification and the quantification of the proteins present. The more samples, the more certain you are that indeed these proteins are there. After you have a higher confidence on the proteins present, then you move to the comparison of your high confidence results. If you compare everything pairwise, then your results and later your comparison will not be as confident as in the other case. But the statistics are applied to the proteins detected and when the confidence is high, then you can compare them


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Why isn't water decompose well like food, although bacteria need water?
Fruits are decomposed by bacteria well.
Although bacteria need water more than other foods,
why isn't water decomposed well like food?

-1, this question makes no sense. What do you mean by water decay? I wouldn't define water as a 'food', do you have a reference that does?

To me the question indeed make some sense. "Water is inert" that is a wrong concept. Water is biologically very active and it take part in all biological pathways. But all the biochemical pathways also give out water in so many places... so water on Earth never finishes as some-other by-product like H2 + O2.

Though those fruit-rotting bacteria requires much watery condition; a large amount of water (on gross); goes to keep the bacterial cytoplasm fluidy.

Interesting thing I found in this question; if all the water got "degraded" by the bacteria into H2 + O2 ; all liquid water would finish up from Earth. However likely bacteria would not go to waste their energy via such a thermodynamically unfavorable 'endergonic' process.

Perfectly good question, for any adult teacher, to understand and answer. Pontification is not the mission of moderators. Clarification IS. Fruits contain cells and sugar which can be eaten by millions of organisms. Water is like rock, an element, and it can only give food to as many animals as it has CO2, N2, Mg, Ca, And other cell constituents dissolved in it. If the water is rich in dissolved rocks and nitrogen, it will produce a lot of life. Stagnant water is older and gives life an easier place to live, and is less filtered by algea.

I agree. The web site is not like a book or Wikipedia. In the original web site, Stack Overflow, users help each other even if the question is duplicated or unclear, by trying to understand what the questioner wants to know, also the answerer shows the link of other answers, when it is duplicated. So I believe that kind of behaviour is needed in this biology section.

It is unclear what you mean by "decay".
Water is not an organic compound (it contains no carbon). It is just $H_2O$. Water cannot rot! Water is typically not considered as "food" as it is not a source of carbon.
Living organisms can split water molecule (through photosynthesis typically, see wiki > water splitting) and synthesize water molecule (through formation of carbon polymers typically) but I doubt this is what you were thinking about.
Note that if you leave water with a source of carbon (dirty water) somewhere, many organisms will be happy to colonize this environment.

-1, I can't see any value in answer a question that is totally unclear.

I've got another answer from other site, water has no nutritious value. So as you mentioned, in dirty water, bacteria can colonize. Hence we can leave a bottle of water on a desk for a long time. Probably dirty water can be decayed. But the bottled water has also an expiration date, right? I was curious for it. Thanks anyway.

@Michael_A An answer should not be judged based on the question. It is not easy to ask clear questions on subject you know little about. I have asked a lot of unclear questions and comments and short answers have helped me even if the question ends up being closed. It would be silly to rebuke any attempt at helping someone just because (s)he failed to formulate a clear question (except maybe when the post clearly shows lack of effort).

@Remi.b, I agree with your reply but I don't think it's relevant to this question + answer. Many very useful answers correct a false premise in the question, I have read, and enjoyed, a number of your answers that were very useful in that regard. It's not clear that you have corrected any false premises with the answer. The comment from Solek indicates that another site provided an answer to whatever the question was. I think this question shows a very clear lack of effort.

I agree there might have more helpful answer in explaining the basics of organic chemistry and why water will not rot. Note btw that I did vote to close the question as unclear right after you did (as it will become obvious if it eventually ever closes).

@Solek Based on your comment, I feel like you are still thinking that water can be decayed. That expiration date on the water bottles is for the plastic that starts leaching chemicals into water. Example can be found in this paper here. Water can be contaminated with waste but not decayed.

I don't think not being an organic compound is the relevant factor here.  After all, you could say that iron 'rots' when it rusts.  What's important is that rot is a bunch of exothermic reactions, so breaking down those organic compounds supplies energy to the microorganisms responsible for it.  Splitting water is an endothermic reaction: you have to put a good bit of energy in to split the molecule.

@Remi.b actually, answers should be judged based on the question. From How do I write a good answer? in the [help], Answer well-asked questions. Not all questions can or should be answered here.

@Remi.b it's actually one of my canned comments that I posted on Meta a while back. It's meant for the occasions when people try to answer god-awful questions where nothing is clear, or there's no research effort whatsoever and the question could be answered by googling the question title, or whatever.

@MattDMo, that was the section I was thinking of with my initial comments. I couldn't locate it.   I remember reading that and thinking, those are some wise words.

I thank Remi.b much for answering this question, especially when I see other comments.


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Under what conditions do laboratories have the need to perform both, colony counting and cell counting?
It seems that the requirements to perform colony counting and cell counting in petri dishes are quite different. This is especially true, because colony counting can be done with the naked eye, even though it can get very tiring.
Since I am interested to find out what tasks most biological labs have to go through, I was wondering whether these two tasks might be requested by the same types of labs.

I don't think people actually count cells on Petri dishes. In my experience, cell counting is done for liquid cultures not for Petri dishes. In this case, you can use counting chambers (microscope slides with a grid)

There is a multitude of reasons to use one or the other.
Colony counting is often used on petri dishes for antibiotic resistance screening for practical reasons. One of the downside of this versus cell counting is the need to incubate the bacteria for 12h+ after you have done your experiment before having the result.
In some cases, you will need to know the concentration of cells you have immediately to perform specific dilutions or calibrations etc, you then use cell counting.
Cell counting is normally done with a liquid culture of the bacteria. it can be used to determine the concentration of the whole culture or count during or shortly after an experiment. Some bacteria will have a hard time growing on solid media or some molecules that you might want to test for resistance are not soluble, so you can't plate them to colony count.
So it basically all depends on your needs for the specific experiment and what you are working with (bacteria, medium, molecules etc.).

Any lab that would like to make the distinction between live and dead cells in a cheap way would use both techniques. You count colonies on petri dishes to get the number of living cells, and count in counting chambers under the microscope to get the total number of cells.
There are easier ways to do this though, for example using this: https://www.thermofisher.com/de/de/home/brands/molecular-probes/key-molecular-probes-products/live-dead-viability-brand-page.html in a flow cytometer. That's not that cheap though.

For mammalian cells (I don't know about bacteria/fungi), you can simply use Trypan blue exclusion or acridine orange/propidium iodide staining to determine the number of cells with intact vs. compromised membranes, which generally correlates to live and dead cells, respectively. Viability dyes are great if you're already doing flow, but I wouldn't use them just for determining live/dead status and nothing else.


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On Deformation of the body due to dipole orientation in the cells
Our bodies are made up of billions of atoms and molecules, and each cell has many molecules with dipoles that are initially random and orient themselves in one specific direction when an electric field is applied.
So with the static fair-weather electric field in the atmosphere being ~150 volts per meter (V/m) near the Earth's surface,the dipoles in molecules of our body would orient themselves and provide charge to the cell thus changing its geometry, then why isn't all of our bodies deformed?

"why all of our bodies deformed"? no. what sort of deformation? 2. Are you sure that Earth have an unbalanced electric field at any specific direction? From where you knew this? 3. On application of electric field above a certain limit creates electric current; of course damage take place. We perceive electric shock. Also, strong natural-electric fields like charge in cloud cause thunder. It also works on us and is fatal. So what is new in that?

@AlwaysConfused sorry that was a typo, I meant "why isn't ". Thanks for pointing that. As for the electric field of earth-The static fair-weather electric field in the atmosphere is ~150 volts per meter (V/m) near the Earth's surface, but it drops exponentially with height to under 1 V/m at 30 km altitude, as the conductivity of the atmosphere increases.

So far I knew yet ; that earth is neutral. Now you are telling that is wrong and representing an unpopular fact. So please provide verifiable, authentic links in your question. 150 V!  per meter? surprising. in which direction? just like Earth's magnetic field? You may write your question in more straightforward way; that would help reach the question to more people. Thanks.

I've seen too many advertisements of science museums showing kid touching van-de-graaff-generator  all the hairs spike out; still no death or shock. Wikipedia:  https://en.wikipedia.org/wiki/Van_de_Graaff_generator#/media/File:Maker_Faire_2008_San_Mateo_115_cropped.JPG.  And https://www.youtube.com/watch?v=jZEFuCxD7BE .surely there is some precausions. but maybe this case is something like that.

@AlwaysConfused please refer here: https://en.m.wikiversity.org/wiki/Natural_electric_field_of_the_Earth.

It was a polite suggestion to improve your question so that it becomes acceptable to more people. Btw never take criticism by this website from heart. This website is by-its-nature very much critic. But it criticise your statements and ideas; not you.

Welcome to the Biology Stack Exchange. Please take the [tour] and carefully read through the [help] to learn more about the site, including what is on-topic and what is not, and how to ask a good question. Please ensure your post is formatted correctly as well


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Hand motor control of the brain
I was watching a documentary (don't remember the name or the URL to the documentary) but they stated that the brain is layered and that each new layer is placed on top of the last. So the most primitive part of the brain that sends a signal to move the fingers actually has no way of moving just one, but in fact sends a message to just open and close the hand. That message is then passed on to a newer part of the brain that then filters it into individual finger movements.
I would like to know if this is true and how is the newer layer of the brain able to take an open-close message and identify what finger to move.
This sounds like a strange way for the brain to work; as I'm typing this message out at 86wpm, how is my brain doing such a complex task of moving all my fingers from an open-close message?

What do you mean with layer? The layers I-VI of the somatosensory cortex?

That is how they described it. during documentary; they stated the brain is comprised of different layers that each evolved at different times. Good chance they were dumbing it down for the show.

If you want detailed scientific understanding, I recommend reading some basic neuroscience textbooks (and take a couple of online lectures) and then the book "The Sensory Hand Neural Mechanisms of Somatic Sensation" by V. B. Mountcastle.

Thanks for the feedback. However, without the link I think this question can only be answered by guessing what was being said. Interpretation of complex matters like the evolution of the brain depend heavily on the context of the statements made. I'm voting to close therefore. If you find that link, I'm more than happy to vote for re-opening.

I'll try to find the link and include it in the question. Thank you for the feedback.


text:
Pigmentation in dermatophytes
Dermatophytes are cutaneous keratophilic fungi. They cause concentric skin lesions. As a sample, usually skin scrapings are collected.
When viewed under the KOH mount, they appear transparent but when cultured, they show varied pigmentation. In fact, there is different pigmentation both on the obverse and reverse of the culture media (SDA), which makes pigmentation a differentiating and identification feature. These colors vary from species to species from red to violet.
So here are my questions

Is the pigment secreted out in the medium or retained in the hyphae?
How are the fungi transparent on a KOH mount.
Why is there a different pigmentation on the obverse and reverse?
Why is there no colour in the skin lesions? There is just erythema
if I'm not mistaken.

If you have such cultures then you could add photograph. As well; did you observed different-coloured portions under microscope? maybe they are not obligate dermatophyte and can produce spore when in culture-medium.


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What are the sites of nutrient digestion and absorption in the human GI tract?
Where does nutrient digestion and then absorption take place for different nutrients along the alimentary tract?

Hi Carlos - Welcome to BiologySE... you're question is a bit vague... especially with the use of the term "food groups" - where have you looked for the answer to this question already?

The saliva from your mouth will slowly start to digest starches.
Then the stomach specializes in digesting protein with enzymes and its highly acidic content.
The small intestine will digest proteins, starchs and carbs (with the help of the enzymes traveling from the stomach).
The liver and pancreas secretions will join in the small intestine will help break down fats and complete digestion.
The small intestin is responsible of absorbing the vast majority of digested nutrients and the water is then mostly absorbed by the colon.
Source: Your Digestive System and How It Works


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Why do cells in the cerebral cortex act as interacting nonlinear oscillators?
I'm not a biologist, but I'd like to know something about EEG analysis.
In particular, I have read that EEG signal derive from cells in the cerebral cortex and hippocampus. And that these cells act as many interacting nonlinear oscillators.
I'd like to understand why they are oscillators and why their behaviour is nonlinear. Many thanks for the help!

This link could probably give you your answer. Sorry that i'm too tired to read and vulgarise it at this time :)


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Transport mechanism in absorption of monosaccharides in small intestine
In the cell membrane of the intestinal cells, there is a mobile carrier protein called Sodium  Dependent Glucose Transporter(SGLT1).It transports glucose and galactose to inside the cell using energy.The energy is derived from sodium-potassium pump (Primary Active Transport).How it is possible cause we need energy in Na-K pump too ?

From my initial reading on this, the SGLT1 does not itself directly use energy in the form of ATP. https://en.wikipedia.org/wiki/Sodium-glucose_transport_proteins It appears the uptake of the sugars by this protein are achieved by cotransport. In this case, they "hitch a ride" into intestinal epithelium by following the flow of sodium ions back into the epithelial cells. The reason the Na+ ions flow into the epithelial cells is because of their higher concentration outside the cells. This concentration gradient is created and maintained by the Na-K Pump. So, ATP is used to create a chemical gradient, higher [Na+] outside compared to inside. Then the natural flow of Na+ down its gradient "drags in" the sugars.

I still dont get the point . Na-K pump uses the ATP to keep the concentration gradient stable. How the ATP is generated by this pump to be source of energy for SGLT1 mechanism ?

The pump uses the energy in ATP to create the gradient. The gradient itself is another form of energy. It is the energy in the gradient that brings in the sugars. Forming a gradient is like blowing up a ballon. Once that balloon is full of air, the compressed air inside wants to rush out. As it does, we can get it to do various chores for us. In this case the higher concentration of Na+ outside the cells is allowed to flow in through the SGLT1. As it does, sugars ride in with the ions. The Na-K Pump keeps pumping Na+ out to keep the process going.


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What is the upper limit of number of SNP based mutation in any protein?
I want to know if there is any upper limit of, how many point mutation a protein can have because of disease or nsSNPs? The general studies only focus mostly on a single or double site mutation of any protein structure.

Aren't you limiting yourself to "one" (SNP)? The more mutations, the more likely the protein will not be functional. Theoretically, there is no upper limit. The more vital the protein, the more likely a SNP will adversely affect the individual, and the more likely more mutations will be lethal.

@anongoodnurse: Actually, I wanted to know same thing. If there is any method to determine, how many mutation makes it lethal (or in other words non existent).

Which protein are you wondering about?

Depends on the protein. Also depends on the kind of substitution that is happening. Some functional proteins can tolerate deletion of huge segments. Selection would happen only if the SNP has an adverse effect under the ambient conditions.


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What is the difference between endometrial lining and endometrial stroma?
This is in the context of embryology whereby the syncytiotrophoblast erodes the endometrial stroma during the penetration and implantation of the zygote.
But I don't know the correct terminology of what exactly has been eroded.


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Gene products of recessive/mutated alleles
I probably would not cite a specific example, but some recessive allele work by encoding for the non-functional form of an enzyme. While the dominant allele encodes for sufficient levels of functional enzyme that the dominant phenotype is present in heterozygous individuals. Will the individual have many uselessly non-functional proteins floating around along with everything else?


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Why do some people become more aggressive when tired?
Why do some people become more aggressive when they are tired? I've been thinking about this question for a few days and my 'hypothesis' is that the neural activity in the prefrontal cortex lessens as the brain prioritises the other more primitive parts of the brain. Is it also so that the amygdala becomes more active when tired for some reason?
I've tried to search for answers on Google but can't find any satisfying ones. Optimally, I'd like to see brain scans and have them explained, but maybe that's asking for too much.

From Poor sleep as a potential causal factor in aggression and violence

In most people poor sleep will not evoke actual physical aggression, but certain individuals, such as forensic psychiatric
  patients, may be particularly vulnerable to the emotional
  dysregulating effects of sleep disturbances

The relation between sleep problems and aggression may be mediated by the negative effect of sleep loss on prefrontal cortical functioning. This most likely contributes to loss of control over emotions, including loss of the regulation of aggressive impulses to context-appropriate behavior.

Other potential contributing mechanisms connecting sleep problems to aggression and violence are most likely found within the central serotonergic and the hypothalamic-pituitary-adrenal-axis. Individual variation within these neurobiological systems may be responsible for amplified aggressive responses induced by sleep loss in certain individuals.

being tired affects the brain in some ways similar to being drunk, it is not so much making you aggressive as impairing your ability to suppress aggression. The amygdala routinely produces aggressive impulses which the prefrontal overrides/suppresses. lack of sleep impairs its ability to override.
https://walkerlab.berkeley.edu/reprints/Yoo-Walker_CurrBiol_2007.pdf


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How to track bacteria/ protozoa, unicellular algae in big volumes?
Is there any special cameras and dyes? If I want to track migration/motion of them in 0.1-0.5 cubic metres.

for 3d imaging, you can maybe use MRI and hyperspectral imageing mostly. MRI requires that you feed the bacteria with something radioactive and then have access to an MRI which costs about 100 euros or 300 euros if you are lucky. you'd be lucky if you could see bacteria in an MRI in water. for practical options, sounds like you should arrange a tank with a system of sampling, so that you can get a drop from zones of the tank and count it later in the microscope. https://en.wikipedia.org/wiki/Staining

what's the time frame?

@comprehensible feed radioactive for MRI?

none of them used mri- this, this, or this. All they used light microscopy.

well, using light microscopy I will see in 2d, as I said I need to see them moving in Volume.

@DanielBay hmm 0.1 cubic metre is pretty large 3d volume.


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is there a constant leakage current across axon even in absence of stimuli?
because of resting potential is their a constant leakage current across membrane due to resistance of membrane and ion pumps continuously pump restore the resting potential ?

yes - and now I have to fill up the minimal amount of characters

Have a look here  -  http://biology.stackexchange.com/questions/36123/if-the-average-resting-potential-of-a-neuron-is-70-mv-why-is-there-such-a-high/36127#36127


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Surgical vs anatomical neck
What is the significance of differentiating anatomical neck and surgical neck of a bone?
What could be criterias for differentiation?
I found an article here that says fractures to surgical neck are benign, could this be a criteria for differentiation?

Most of the time, I have heard this differentiation in context of Humerus bone only. In that context, have a look at the wiki pages on the anatomical and the surgical necks.
From this, and what I remember from anatomy class, this distinction is more a functional; practical distinction rather than that based on strictly defined criteria. Surgical neck denotes the most commonly fractured region of the bone, and also the region most likely to damage the axillary nerve passing nearby, and hence would have the greatest representation in an orthopedic clinic. The anatomical neck, on the other end, is the classical distinction based on the centers of ossification and the insertion of the capsular ligament of the adjacent shoulder joint, which gives a greater weightage to its origin and to the anatomical relations (insertions, etc).


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Where can I find these frequencies for several species?
Where can I find frequencies of nucleotides in the DNA for several species?

You mean the specific AT/GC content?

Assuming you mean AT/GC content, then this page wikipedia offers a table and links.

Since most of the genomes consist of double helix DNA, the only meaningful ratio is GC-content. A comprehensive list of the known genomes that includes GC-content data is available at NCBI (note that default Overview tab doesn't contain the GC-content numbers, you need to select another tab, e.g. Prokaryotes). They also provide an FTP access to the raw data, if you need to process the numbers with software.
If you're interested in particular genomes that are not present in this list, you can calculate all frequencies from the sequence. There are a number of programs to do this. For sequences in FASTA format you even don't need a special software, the analysis can be performed with standard tools, e.g. grep (should be installed in Linux/BSD/MacOSX, obtainable for other systems):
grep -v '^>' sequence.fasta | grep -o '[ATGCatgc]' > tmp
# number of AT pairs
grep -c '[ATat]' tmp
# number of GC pairs
grep -c '[GCgc]' tmp


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How would a herbivore's digestive tract differ from a human's?
How would a herbivore's digestive tract differ from a human's? What are parts (organs, tissues, etc.) or enzymes that can't be found in one but is in the other? Also, is it correct to say that a herbivore's digestive tract would be more complex than a human's because herbivore diets tend to  contain a lot of complex carbohydrates to digest?

it's a bit of simple quesiton... you would have such a more studied answer if you just look at cow digestion online. For one, vegetarianism requires a longer digestive tract, i.e. 5 stomachs and bigger intestines. and they have different intestinal flora than specialized animals of all other kinds. https://en.wikipedia.org/wiki/Ruminant#Ruminant_physiology

It depends on the method of digestion the herbivore utilizes and what they eat, grasses, leaves, fruit, or nuts . Ruminants are only one form of herbivore. A wonderful introduction to the various methods can be foundd here. http://vetsci.co.uk/2010/05/14/comparative-digestion/#
For comparison gorilla which are far more herbivorous than human have a much longer small intestines which is one reason they need a much wider trunk. They also of course need larger teeth with thicker enamel and much larger jaw muscles to chew the tough plant fibers. Not so much more complex digestive systems just bigger/longer.

Cutting/pasting an entire answer is not a good way to answer a question on any SE site. Please look at the answers section of the help section.

Good point let me fix it.

Happily removed my DV and replaced with an UV.

Herbivorous animals certainly tend to have very different digestive tracts to humans, or other carni-/omnivores.  In general, mammals cannot produce enzymes that will digest cellulose, so if an animal is to use cellulose as an energy source there must be another way of extracting its energy.  Principally, this is fermentation.
Fermentation is the process of bacterial breakdown of a sugar-like compound to other molecules, such as gases, acids or alcohol.  Herbivores provide an internal environment that is hospitable to cellulose-fermenting bacteria, and provide them with cellulose (by eating plants!).  They then use the breakdown products of fermentation as an energy source - often the relevant compounds are volatile fatty acids.
Different species have solved the problem of having an internal fermentation chamber in different ways.  Cattle, as many people are aware, have a complex and expanded foregut, and regurgitate their stomach contents to allow further mechanical digestion.  Horses have a vastly expanded hindgut (caecum and large intestine).  Rabbits have an expanded hindgut, and also eat (certain types of) their droppings to allow further mechanical digestion.
One other difference that we can observe in herbivores is in the structure of their teeth.  A carnivore such as a lion will have sharp, pointed teeth and a wide opening jaw to allow catching and killing prey, and tearing of flesh.  Herbivores have broad, flat teeth with rough occlusal surfaces to allow efficient crushing of prehended food.  They may also have adaptations for dental longevity - the horse, for example, has hypsodont or long rooted teeth, that erupt through its lifetime to combat the wear of extended chewing of rough material.

Welcome to SE Biology. This answer would be improved with some links that confirm your main points. Irrespective, +1 from me.

The information contained in this post requires additional references. Please [edit] to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

The digestive tracts of ruminants (cud chewers) such as
cattle, goats, and sheep are specialized to maximize the benefits
of their endosymbiotic microorganisms. In place of the
usual mammalian stomach, ruminants have a large, four chambered
organ.
The first two chambers, the
rumen and the reticulum, are packed with anaerobic microorganisms
that break down cellulose by fermentation.
The ruminant
periodically regurgitates the contents of the rumen
(the cud) into the mouth for rechewing. When the more thoroughly
ground-up vegetable fibers are swallowed again, they
present more surface area to the microorganisms for their digestive
actions.
The microorganisms in the rumen and reticulum metabolize
cellulose and other nutrients to simple fatty acids, which
become nutrients for their host.
The food leaving the rumen carries with it enormous numbers
of cellulose-fermenting microorganisms. This mixture
passes through the omasum, where it is concentrated by water
absorption.
It then enters the true stomach, the abomasum,
which secretes hydrochloric acid and proteases. The microorganisms
are killed by the acid, digested by the proteases, and
passed on to the small intestine for further digestion and absorption.
The rate of multiplication of microorganisms in the
rumen is great enough to offset their loss, so a well-balanced,
mutually beneficial relationship is maintained.
It would be more correct to say that Herbivores have special adaptations for digesting cellulose rather than complex as humans also have a complex digesting system.
Hope that helps you.

"The rate of multiplication of microorganisms in the rumen is great enough to offset their loss, so a well-balanced, mutually beneficial relationship is maintained." -- well that's how it should work - in modern farming feeding practices often result in derogation of the rumenal bacterial population.


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On the premise of crop rotation, is there similarly a plant or organism able to provide nutrients into its environment that exists in water biomes?
I know of the simple concept of crop rotation, and being able to use certain plants to replenish soil, and was wondering if there is a plant or organism that can or does function similarly but in water. I also know there are some plants that are more resilient (and even function or thrive) in soils high in certain compounds and metals (or, conversely lacking in certain nutrients or conditions), that are otherwise detrimental for other plants or organisms. I am therefore also wondering which plants or organisms function similarly, but again--in water, rather than on land.
I have a particular interest in saltwater environments, but also would like to know if there is something in freshwater environments that provides this function.

The question isn't worded very clearly. Scientifically you cannot talk about crop rotation for natural ecology. Ecology has mutualism, commencalism, companion plants that grow together, i.e. some lichen that have three organisms together, plant, mushroom and bacteria, in sponges growing on trees and on rocks.
Crop rotation is especially important on land because we do monocultures, and our sewage doesnt go back into the field, there is a net drain on the soil minerals. In forests and the sea, the situation is different, because plants adapted to the soil grow and build up nutrients over time by rotting with organisms, being fertilized by worms, snails, insects birds and so forth. In the sea, fish provide that function and there isn't the same net drain on a sea environment as there is in a crop.
If you study green life inside different pots of water, from river, tap, rain, and pond, from different sources and different geologies, you will learn some things about aquatic ecology and nutrients. It reacts  with different plants and at different speeds.
The sea is physically so different from land, that the matter falling from the top can be transported miles away, that little comparison is made between nitrogen fixing in soil and in seawater. Also, the zone with the most light also has the strongest currents, so less chance for exchange of nutrients in ecology micro-climates and biomes.
crop rotation is mostly for N P K fixation.
On land NPK availability is often due to the acidity of the geology, which is not quite the same in the sea, plants can live on basalt or chalk, but they have endless flowing water and a good detritus layer in either.
In the sea, NPK is mostly brought by algea and cyanobacteria, which fall and bring it to the phito-detritus layer.
There are not the same forest type ecosystems in the sea as on land, where forests create many meters of peat bogs and massive NPK reserves, as in jungles sometimes. Because forests are less complex in the sea, less green stuff exists on the sea bed, we can say that the situation for plants is less profitable than on land and that instead the biomass exists more in floating small algea, Coccolithophores and so forth, which account invisible for most of the algal biomass of the sea. I cant find if there is more phyto biomass in the land or in the sea. I figure it's on land.
In freshwater environmetns, lakes can have an over or under abundance of NPK, and can bloom more or less completely for a given Ph and environment, given specific adaptations that help them to cope with a particular Ph. it's a lot more variable that the sea with PH going from 4 to 10 and beyond, when the sea ph is about 7.5-8.4.


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How do detergents interfere with protein assays?
This has been getting me stuck. I've tried to understand what a detergent would do in an assay, but I can't figure out whether it would affect the protein or the reagent (say, in a Bradford assay).

Depending on the detergent, its concentration, and the exact assay being performed, it can affect both the protein and the assay reagent(s). Some detergents will bind the (usually colorimetric) reagent, or otherwise chemically react with it, giving high background to your assay and sometimes completely masking the specific signal of the assay itself. Many modern protein assays are tolerant of a fairly low level of various detergents, perhaps some but not others, and this underscores the necessity of running a buffer/diluent-only control to verify the background of your measurements. Other assays, like Bio-Rad's DC Protein Assay or the Pierce Detergent Compatible Bradford Assay Kit from ThermoFisher, are engineered to tolerate a certain (often fairly high) level of detergent without increasing the background of the assay.


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What is the difference between a "semi-contracted" muscle and a "contracted" muscle?
I read on http://www.spine-health.com/glossary/muscle-tension:

Muscle tension refers to the condition in which muscles of the body remain semi-contracted for an extended period.

What is the difference between a "semi-contracted" muscle and a "contracted" muscle?

If you consider the length of a muscle can vary from resting length to shortest length, my guess is that semi-contracted is somewhere in between. I believe that spine-health.com isn't being entirely clear with their definitions.

I think they're refering to rate coding and motor unit recruitment.


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Why is hunting big animals more dangerous for the species?
I've heard in a lecture about protection of primates that one reason the classical population dynamics doesn't work is that the aboriginal hunters tend to hunt the big, strong and healthy individuals that have the best chance of becoming a successful parent.
Is this effect really so significant that it outweighs the fact that the hunters don't have to hunt so many of them in order to get the same amount of meat?
[Additional explanation]:
This question asks about the best strategy in protecting rare wild animal species against excessive hunting. We don't have to intervene when lions hunt zebras because less zebras means less food for lions - so the ratio of zebras and lions doesn't change much so there's no danger of any species getting extinct. Unlike the natural predators and prey, it has been found that the amount of meet hunted by people in forests isn't anyhow dependant on the number of animals living in the nature because humans use tools which give them a huge advantage over the "prey". Also, number of people living in a forest isn't  dependent on the sources in the wild, due to the rise of agriculture.
There was a research how much is the size of an animal connected to the probability a hunter will hunt specifically this animal and it has been found that the hunters tend to pick the physically biggest, strongest and healthiest individuals. This phenomenon has been marked as dangerous for the future preservation of wild species because (that's my guess) the most healthy and strong are the most likely to rear healthy offspring. I said to myself that from what I've learned about evolution, the difference between the physical fitness of an individual feed by a less strong parent (compared to the rest of the population) and an individual feed by a stronger parent can't be so big that it overweighs the fact that when a hunter hunts smaller animals, he's more likely to hunt more of them (That's something that has been studied) so the overall number of hunted animals is actually bigger. So my question is, wheter I'm correct or wheter the factor of the bigger number of animals you hunt when you hunt small animals actually isn't as important as the fact that healthy and strong parents will rear healthy and strong offspring.

For some reason I have a difficulty understanding your question... as if one variable is missing.. can you clarify? in what relation is hunting big animals dangerous to which species? the species being hunted or us humans? one thing could for example be if you look at sweden... the bigger the animal, the bigger the offspring. how likely would it be for a wolf to attack a big moose, rather than a small moose? maybe it has something to do with the species being able to protect itself?

@Hallur I edited the question to make it clearer. Yes, the animals are endangered by the hunters who kill them.

keep in mind primates take a long time to reproduce and reach maturity, many times when you kill a parent you are also killing living but not fully grown offspring, and for many primates it can also destabilize the society as well, which hurts everyone and can cause more subsequent deaths. The largest healthiest primate tend to also be the highest standing in the trope, so killing them can trigger infighting and infanticide.

@John Oh yes, the nutritional differences can definitely play a role. It just seems to me that when you kill an animal before its reproductive age, you affect the nature much more.

Size is not the same thing as as age, primates can vary quite a bit in size and health independent of age. the biggest in not automatically the oldest. in an interdependent social species the rank of the individual has other effects. think of it like the difference between the president dying and a homeless guy dying while both are regrettable one has a much stronger effect on the rest of the population.

@John Hmm...I guess the assumption that the size doesn't say much about the age is too general to be the case. But you have a point, the stronger individuals should be better at providing nutrients for the others.

This question still doesn't make any sense. I can't understand what you're asking at all - can you frame your question in a single, easy-to-understand, grammatically-correct sentence? Are you asking about how humans affect the evolution of primates? Which ones? Or are you asking about the effects of killing a prime figure in a family unit on the offspring? Please clarify exactly what kind of situation you are asking about, and what your question actually is. Some citations supporting the ideas presented in your question as facts would also be useful.

I can see two different sides to this question.
On one side,
From Darwin's Theory of Evolution, the more adapted you are, the better chance at reproducing you will have, thus passing on your genes.

"Survival of the fittest" is a phrase that originated from Darwinian
  evolutionary theory as a way of describing the mechanism of natural
  selection. The biological concept of fitness is defined as
  reproductive success.

In this case, you hunt the fittest, strongest animals that can procreate and protect their descendants, leaving the weakest alive. The weakest may not be able to continue the lineage because of their weakest gene pool and the species existence could be at stake.
On the other side,
A reputated Oxford Zoologist, Richard Dawkins wrote:

We are survival machines – robot vehicles blindly programmed to
  preserve the selfish molecules known as genes

In this particular example, being strong, fit and healthy could be interpreted as being unfit for evolution, since it attracts predators (humans) to kill, as would not be the case for medium sized less meaty healthy individuals. The true adaptation that could make the specie survive in this case is via the weakest members that are not worth the effort to be hunted but still can survive other threats.
There is several more viewpoints that could be described knowing more details about exactly which animals, their environnement, the other predators and the exact contribution of the "healthy strongest" specimens you described as being hunted.
Nevertheless, hunting animals can always endanger the specie depending on the frequency of the hunt, frequency of the animal reproduction and several other factors, so can many other human behaviors.
Source: The selfish gene - Richard Dawkins (Book)

Sorry, you got it wrong. When I wrote that it is dangerous for the species when the hunters hunt the stronger individuals more often, I didn't mean it could cause troubles due to the selective pressure, I meant that when a parent is healthy and strong, it probably doesn't lack nutrients himself, so it can't fully concentrate its effort towards providing food for the offspring. Also there is a better chance the offspring will even born and grow up healthy.

@Probably"when a parent is healthy and strong, it probably doesn't lack nutrients himself, so it can't fully concentrate its effort towards providing food for the offspring"  This makes no sense. Your comment is as clear as your question was before Hallur's edit...

@Probably I answered the question "Why is hunting big animals more dangerous for the species?". Evolution has it's say in this because it will truly determine the degree at which hunting the big animals affects the survival of the specie (i.e the "dangerouseness for the specie"). Take it as an answer in the long time, this can be discussed a lot since it isn't a specific scenario that can be studied but rather a general question.

It was my edit and I'm not talking about evolutionary disadvantage, I'm talking about disadvantage in physical fitness (yes, it is being passed on from parent to offspring as well to a certain extent.)

@Probably I think you are misunderstanding the lecture you heard. If the lecturer was talking about fitness, they almost certainly meant it in an evolutionary context. If you hunt the strongest animals, you are culling those who have been most successful in their environment. Leaving behind only the evolutionarily weaker animals means that the next generation may be weaker as well. Smaller animals could also be young/not sexually mature, so you reduce a population's rate of reproduction by taking out the animals that would otherwise have the best chance to reproduce successfully.


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Sodium concentration during action potential generation

At the peak of the graph, is the concentration of Na+ outside the cell more than inside? That must be to overcome the electrical force in the opposite direction.
When is the concentration of Na+ greatest inside the cell? At the peak assuming the Na+ channel close immediately at it then it is also greatest at 3. If there is still passage of Na+ then 3 is the maximum. Is this true or false?
One last question: is the inside of membrane actually negative, or only negative relative to the outside? In a galvanic cell for example, a given rod isn't actually negative, but it is negative relative to another.

As you said, it is negative relative to another.

This was the very first result on google, and I reckon that the calculations are correct: http://www.physiologyweb.com/lecture_notes/neuronal_action_potential/neuronal_action_potential_na_and_k_concentrations_do_not_change_during_an_action_potential.html

Very good question. I use it routinely when I teach basic neurophysiology. The key to the answer is to understand that the change in the membrane potential is not caused by transport of large amounts of ions over the membrane. It is simply the change in permeability of the membrane to these ions that change the potential. The membrane potential can be calculated by the Goldman equation from the permeabilities of the individual ions ($\ p_x$ indicates the permeability of ion X).
$\ E_m = \frac{RT}{F} \ln{ \left( \frac{ P_{\text{Na}}[\text{Na}^{+}]_\mathrm{out} + P_{\text{K}}[\text{K}^{+}]_\mathrm{out} + P_{\text{Cl}}[\text{Cl}^{-}]_\mathrm{in} }{ P_{\text{Na}}[\text{Na}^{+}]_\mathrm{in} + P_{\text{K}}[\text{K}^{+}]_{\mathrm{in}} + P_{\text{Cl}}[\text{Cl}^{-}]_\mathrm{out} } \right) }$
It is therefore not the transfer of charges as such that drive the change in membrane potential, but a small amount of ions must be moved to counteract the capacitive properties of the cell membrane. The cell membrane acts as a capactor, which means that the voltage across the cell membrane cannot change instantly, but changes as charges are redistributed between the two sides. These charges are moved by Na and K ions moving through the channels in the membrane.
Because we can model the membrane as a capacitor in an electric equivalent circuit, we can estimate the amount of ions moved during the AP. The charge (Q) across a capacitor (cell membrane) is measured in Coulomb (C) and calculated as the product of the capacitance and the voltage across the capacitor: $\ Q=C_m V_m$. If we assume a spherical cell with diameter 10µm and a membrane capacitance of 1$\mu F/cm^2 $ (= $\ 0.01F/m^2 $) and for simplicity assume that the membrane potential changes by 0.1V during an action potential (from -70 mV to +30 mV), we can calculate the number of charges moved.
The total capacity of the cell membrane is $\ 4\times\pi \times (5\times10^{-6}m)^2 \times 0.01F/m^2 = 3.14\times10^{-10}F $. As we change the voltage by 0.1V, this means that we must move a charge of $\ 3.14\times10^{-10}F\times0.1V=3.14\times10^{-11}C $ across the membrane. Given that the charge carried by one monovalent ion (the elementary charge) is $\ 1.6\times10^{-19}C$ we must move $\ 2\times10^6$ ions.
The volume of the cell is $\ \frac43\pi\times(5\times10^{-6}m)^3 =5.24\times10^{-16}m^3=5.24\times10^{-13}l$. If we assume intracellular concentrations at the start of the action potential to be [Na+] = 0.01M and [K+] = 0.15M we can calculate the number of Na+ and K+ ions in the cell by multiplying with Avogadro's number ($\ A_N = 6.02\times10^{23}$). Thus: number of Na+ ions = $\ 0.01M\times5.24\times10^{-13}l\times6.02\times10^{23}=3\times10^9$ and number of K+ ions = $\ 4.7\times10^{10}$.
Given that $\ 2\times10^6$ Na+ ions were moved into the cell during an AP and the same number of K+ ions moved out, the percent change in concentration can be calculated. The change in $\ [Na^+]$ due to one AP is therefore $\ \frac{2\times10^6}{3\times10^9}\times100\ percent=0.07\ percent $
and the change in $\ [K^+]$ is  $\ \frac{4.7\times10^{10}}{3\times10^9}\times100\ percent=0.004\ percent$
In conclusion, the changes in intracellular concentrations of Na and K during a single action potential is insignficant, and can easily be counterbalanced by the continuous action of the Na/K-ATPase. In most cases, even if the nerve cell fires repeatedly at high rates, there is no measurable change in concentrations.

Below is a schoolbook example of the membrane potential combined with the individual conductivities of Na+ and K+ during an action potential (AP) (Fig. 1);

Fig. 1. Membrane potential and conductivities of the two most important ions in AP generation. source: Physiology Web
And in Fig. 2 is an example of the currents of Na+ and K+ during an action potential (AP) (Fig. 1). Note that K+ stays high due to amanipulation of ion concetrations.

Fig. 2. Sodium and potassium currents during AP generation.
However, you ask about the concentrations of Na+ in the cell. As far as I know, this has not been investigated directly. Intracellular Ca2+ concentrations, for example, can be imaged with various imaging techniques, but absolute Na+ and K+ concentrations have to be measured with intracellular electrodes. So while the conductivities and the currents are depicted quite clearly in the above figures, they do not show the absolute concentrations of Na+ or K+ and I doubt it can be found anywhere in the literature. It can of course be mathematically deduced, by calculating the number of ions entering the cell using the Nernst equation and correcting that for the background effect of the sodium-potassium pump and other factors that alter Na+ concentration in the cell (protein transporters and what not). It will at least give an approximation of [Na+]i.

Thank for the information about the current and how absolute concentration weren't measured.
Can you just solve this question for me?
At the peak of the graph, Is the concentration of Na outside the cell is more than inside? because that must be to overcome the electrical force in the opposite direction
Because our book shows that at the peak the concentration of Na outside is lower than inside which is not reasonable to me.

@user3733086 the idea I have is that, even though the peak Na+ concentration inside is still greater than outside, the amount of Na+ that exits the cell is sufficient to revert the the electric potential. Remember that there are other ions intervening, and that the potential differences are measured in mV

See my answer to another question: the emphasis there is on resting potential but it is relevant to this one too. tl;dr: Very few ions actually move across the membrane (relative to the total number of ions present) during an action potential. The intracellular concentration of sodium does not change much during a spike, far less than 1%.


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Do we understand how (some) proteins work?
Are there proteins whose operation we can describe from first principles using chemistry or physics?
I've had introductory college courses in biology, and some classes in neuroscience, so I know that the behavior or purpose of many proteins is well characterized. But the descriptions of how proteins work—at least in what I've read—are always sort of similar and vague, “X binds to Y and the shape of the protein changes, which does Z”. At the level of the material I'm reading, I wouldn't necessarily expect much more, but I am curious whether researchers actually have a more detailed understanding of how proteins work. Can we describe the way that (some) proteins work in the same way that an engineer can describe how an internal combustion engine works?

That depends strongly on the resolution scale you want to look at. How ribosomes work (a classical example for a molecular machinery) is pretty well understood, though surely not the binding partners for each and every amino acid in these huge complexes is known.

Ribosomes aren't really proteins, but yes we do understand how some individual proteins work, the problem is that the interactions of charge , shape,and bonding on each amino acid interact with each other so the larger the proteins the more difficult it is to understand all of the layered interactions. that's why de novo protein design is so difficult and why even simple design needs computers. If you want to learn more "Protein structure prediction"  or "Bioinformatics" are good search terms. Or you can get started here, https://www.expasy.org/proteomics

Yes. Hemoglobin is a very well studied example.

Yes. For a number of proteins, including certain classes of enzymes, we have a very good biochemical idea of how the reaction catalysis works - the metal catalyst ion binds to these amino acids here, the substrate binds to these other residues like so, and in doing so induces a conformational change bringing the catalytic ion and a water molecule in close proximity to the substrate, where X chemical reaction takes place, then the substrate is released and the reaction center is recharged likewise.


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Was mammal body better suited for some type of the marine environment than the body of fish?
When some of the land mammals came back to the oceans, they seem to be successful in the competition with fish at least in some environment even though they seem to have a huge disadvantage in the need of breathing above the water. So how did they succeed in the competition with fish?

I think you have cause and effect reversed.  Marine mammals probably didn't start out competing with fish, they started eating fish.  A bear, for instance, isn't particularly adapted to marine life, yet can (in suitable environments) catch & eat them successfully.  Over time the more successful fishers might evolve to look like otters, say, and then seals...

Ok, so the main advantage was the size? I assume there were no bigger predators in the seas before. If you could link me any source, I'd consider this a nice answer ;)

Sharks can be pretty large - I think bigger than most land mammals, and a good many marine ones.  Other fish like tuna & swordfish can be pretty big, too.  These (or their ancestors) all existed for many milliions of years before marine mammals, but coexisted with ichthyosaurs, pleisosaurs, mosasaurs, &c.  It isn't necessary that mammals displaced prior predators, only that they could catch enough small fish to survive & reproduce.

By asking So how did they succeed in the competition with fish? you are making the false assumption that they had somehow to succeed at some form of competition. What lead you to this false assumption is I think either of the following two mistakes..

A misunderstanding of the principle of competitive exclusion.
A false assumption about the existing overlap between marine mammals ecological niche and fishes ecological niches

Competitive exclusion
The principle of competitive exclusion states that two species occupying exactly the same ecological niche cannot stably coexist. One must either become extinct or shifts its ecological niche (process that is known as character displacement).
A consequence of the above is that if two species have ecological niches that partially overlap, they can still stably co-exist.
Ecological niche of marine mammals
There are two independent lineages of mammals that evolve marine life (cetacea and sirenia). I don't know which one you have in mind when asking the question and a sensitive complete answer would depend on the lineage of interest. However, in any case, there is such a diversity of ecological niches in fishes that it is hard to really fully address the question.
Marine mammals occupy different ecological niches. There is no question of whether one has an advantage over the other as the species do not compete for the same ressources.
A typically important reason for why marine mammals and most fishes occupy different ecological niches relate to their size differences. Simply put, mammals to be quite big! For example a orca eat fishes (and other things) that had few predators before. There is therefore not much competition involved.
Just to reiterate... in your comment you say so the main advantage was the size?. Size was one of the biggest reason why they would be able to occupy previously unoccupied ecological niches. But it is not an advantage toward competition with fishes as you seem to be thinking as there probably little competition.


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when does an erythrocyte start carrying oxygen molecules and what is the binding capacity
As it is in the title, I am just wondering when does an erythrocyte (especially Reticulocyte) start carrying oxygen molecules and what is the binding capacity for oxygen.
That is, Under normal conditions, reticulocytes are the youngest erythrocytes released from the bone marrow into circulating blood. They mature for 1-3 days within the bone marrow and circulate for 1-2 days before becoming mature erythrocytes. How much oxygen molecule a reticulocytes can carry ?
I mean, I need an approximation of the number of O2 molecules bound to hemoglobin per reticulocyte

Erythrocytes contain many hemoglobin proteins. Each protein has 4 haem groups, and oxygen molecules bind to in porrin ring inside these haem groups. The binding capacity is the affinity each haem group has for oxygen. This changes depending on the external conditions, for example PH.
For example, when the ph is quite low (acidic), this is often due to CO2 build up in the local area, dissolving in the blood to form carbonic acid. This means that there is anaerobic activity happening in the area so it needs more oxygen. The oxygen associated with the hemoglobin will disassociate making it available for the surrounding tissue. It is important to remember that the process is not concrete and is always fluctuating. There are many curves that show the likelihood of association and disassociation. I would recommend looking at these disassociation curves to understand.
Erythrocytes are typically oxygenated in the lungs (supplied by the pulmonary artery from the heart). After oxygenation, the blood goes back to the heart via the pulmonary vein in order to be sent round the body. Reticulocytes are immature erythrocytes and will be carrying increased amounts of haemoglobin as they develop it. The following link leads to a paper which approximates haemoglobin content in reticulocytes.

https://www.ncbi.nlm.nih.gov/pubmed/18027835

Thank you for your answer and the link. I updated my question

@bantandor what specifically about this answer and the linked paper don't answer your question, or give you the tools to find the answer on your own? Are you looking for an approximation of the number of $O_2$ molecules bound to hemoglobin per reticulocyte? You need to be clear about what you're asking for, and be willing to do some research on your own.

Actually, yes I am looking for an approximation of the number of O2 molecules bound to hemoglobin per reticulocyte


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What scorpion is this and is it lethal?

Found indoors in Florianopolis, Brazil.
Is able to hang from a web like something inside the jar.

I have another photo of the underside but cannot add because of reputation.

It's it a spider? Had it been a scorpion it would have been armed with a  sting.

It is a spider. Note the spinnerets at the caudal end of the abdomen, and the absence of claws. An eye pattern would be really nice; I think it's a jumping spider of some kind.