21. Which statement is   correct   for fatty acid biosynthesis?
(A) Double bonds can be introduced in Golgi body.
(B) Chain lengthening occurs either in ribosome or endoplasmic reticulum.
(C) The carbon source at site of endoplasmic reticulum is malonyl-ACP.
(D) Ribosome is the principle enzyme for fatty acid biosynthesis.
(E) Carbon dioxide is involved in the formation of malonyl-CoA.

17. Aminotransferases are enzymes that have all of the following characteristics   except  : (A) can make an α-keto acid from an α-amino acid. (B) use pyridoxal phosphate as a carrier of amino groups. (C) catalyze highly reversible reactions. (D) use ATP. (E) serum levels are used as a clinical measure of tissue damage.

18. Which amino acid is the precursor of the methyl group donor in biological methylation? (A) Tryptophan. (B) Histidine. (C) Methionine. (D) Arginine. (E) Lysine.

19. What situation is most likely to the formation of ketone bodies? (A) Starvation. (B) Diabetes not suitably controlled. (C) Intake high in lipids, low in carbohydrates. (D) All of the above. (E) None of the above.

20. What effect do ketone bodies have on blood pH? (A) Lower blood pH. (B) Increase blood pH. (C) Neutralize blood pH. (D) No effect on blood pH. (E) Can't determine.

22. Where does the fatty acid synthesis occur in the cell? (A) Autophagosome. (B) Cytoplasm. (C) Mitochondrial matrix. (D) Golgi body. (E) Inner mitochondrial membrane.

23. In analytical ultracentrifugation the sedimentation coefficient, which is expressed in Svedberg units (S), characterizes a sedimenting particle on the basis of: (A) size only. (B) shape only. (C) charge only. (D) both size and shape. (E) None of these.

24. Which of the following statements is   true  ? (A) In order to replicate both DNA strands, E. coli synthesizes each strand in the opposite direction (one 5'-3', one 3'-5'), so they can be synthesized at once. (B) Okazaki fragments are short DNA pieces that explain how DNA is synthesized on the leading strand. (C) A primer strand in DNA replication is needed because it ensures the fidelity of the newly synthesized DNA strand. (D) DNA repair mechanisms are essentially the same whether the DNA has minor damage or major damage.

25. The cyclic form of sugars (A) has one more chiral center than the open-chain form. (B) loses a chiral center compared to the open-chain form. (C) is not usually found in nature. (D) has one more carbon atom than the open-chain form. (E) has one less carbon atom than the open-chain form.

複選題26. Mr. Bean synthesizes a pentapeptide "DPRTH". Choose the   correct   answer from the following descriptions (pK₂ of the N-terminal amino group of the peptide is 9.1； pK₁ of the C-terminal carboxyl group of the peptide is 2.1； pKa of D is 3.65, pKa of R is 12.5, pKa of H is 6): (A) The pI value of the peptide is around 4. (B) The pI value of the peptide is around 7. (C) The pI value of the peptide is around 11. (D) When 0.1 mg of the peptide is dissolved in 100 mM Tris (pH 9), it could bind to a cation exchange column. (E) All the residues in this peptide contain one chiral center only.

27. Which of the following statements about protein-ligand binding is   correct  ? (A) The (association constant) is equal to the concentration of ligand when all of the binding sites are occupied. (B) The is independent of such conditions as salt concentration and pH. (C) The larger the , the weaker the affinity. (D) The larger the , the smaller the (dissociation constant). (E) The larger the , the faster the binding.