15. The function of a molecular chaperone is to: A.act as an energy source during the polymerization of amino acids into a polypeptide. B.act as a carrier molecule and bring “activated” monomers to a polymer for incorporation. C.bind to specific structures on the polypeptide in order to assist the folding of a protein into its correct three dimensional shape. D.unfold proteins with the incorrect three-dimensional shape and refold them into the proper shape. E.transport rRNA from the nucleus to the cytoplasm. Answer: C (The structure and function of macromolecules, fig. 5.26, pp. 79–80) Chaperonins (also called chaperone proteins) are protein molecules that assist in the proper folding of other proteins. Molecular chaperones do not actually specify the correct final structure of a polypeptide. They work instead by keeping the new polypeptide segregated from “bad influences” in the cytoplasmic environment while it spontaneously folds.
16. Ethidium Bromide is used in electrophoresis of DNA fragments because it:
17. The species Homo sapiens first appeared in which geologic epoch?