20.A purified peptide was treated with Cyanogen Bromide (CNBr), resulting in two fragments. Treatment of the original peptide with Trypsin yielded three fragments. Chymotrypsin treatment resulted in no cleavage. Recall the specific cleavage sites for Trypsin (positively charged side chains) and Chymotrypsin (aromatic side chains). Which sequence is consistent with these findings? (A) Met-Gly-Phe-Lys-Ala-Gly (B) Ala-Met-Lys-Arg-Gly-Gly (C) Arg-Lys-Met-Tyr-Ser-Gly (D) Gly-Met-Arg-Lys-Trp-Gly (E) Lys-Met-Phe-Arg-Ala-Gly

9. Phospholipids are the primary structural components of the cell membrane bilayer. Which of the following descriptions regarding the function of phospholipids in the membrane bilayer is the most accurate? (A) Phospholipids, through their amphipathic nature, spontaneously form a barrier that prevents the free movement of water-soluble substances in and out of the cell. (B) The primary function of phospholipids is to act as active transport pumps, directly consuming ATP to move ions across the membrane. (C) Phospholipids remain in a fixed, static state within the membrane to provide mechanical rigidity and replace the need for a cytoskeleton. (D) The main function of phospholipids is to act as enzymes that catalyze the translation and modification of membrane (E) proteins. Phospholipids use their hydrophilic tails to create channels in the membrane core to facilitate the simple diffusion of large polar molecules.

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