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}
