def make_secondary_structure(pdb_dict):
    """Creates a dictionary of helices and strands, with each having a list of
    start and end residues.

    :param pdb_dict: the .pdb dict to read.
    :rtype: ``dict``"""

    helices, strands = [], []
    for helix in pdb_dict.get("HELIX", []):
        helices.append([
         f"{helix[19]}.{helix[21:25].strip()}{helix[25].strip()}",
         f"{helix[31]}.{helix[33:37].strip()}{helix[37].strip() if len(helix) > 37 else ''}",
        ])
    for strand in pdb_dict.get("SHEET", []):
        strands.append([
         f"{strand[21]}.{strand[22:26].strip()}{strand[26].strip()}",
         f"{strand[32]}.{strand[33:37].strip()}{strand[37].strip() if len(strand) > 37 else ''}",
        ])
    return {"helices": helices, "strands": strands}