def find_orphans(model):
    """
    Return metabolites that are only consumed in reactions.

    Parameters
    ----------
    model : cobra.Model
        The metabolic model under investigation.

    """
    return [met for met in model.metabolites
            if (len(met.reactions) > 0) and all(
                (not rxn.reversibility) and (rxn.metabolites[met] < 0)
                for rxn in met.reactions)]