23. The brain prefers to use _____ as fuel, but under prolonged fasting or starvation it adapts to use _____.
(A) fatty acids； glucose.
(B) glucose； β-hydroxybutyrate.
(C) glycogen； fatty acids.
(D) glucose； fatty acids.
(E) β-hydroxybutyrate； amino acids.

19. The _____ of pyruvate to acetyl-CoA is catalyzed by _____ (A) decarboxylation； pyruvate decarboxylase (B) carboxylation； pyruvate carboxylase (C) transacylation； pyruvate transacylase (D) dehydration； pyruvate dehydration complex (E) decarboxylation； pyruvate dehydrogenase complex

20. The anaplerotic reactions associated with the TCA cycle are a result of the: (A) use of many of the TCA cycle intermediates in biosynthesis. (B) decarboxylation reactions. (C) irreversible nature of some of the TCA cycle reactions. (D) oxidative nature of the TCA cycle. (E) production of GTP and reduced coenzymes.

21. ATP made in glycolysis and the TCA cycle is the result of _____ phosphorylation, and NADH-dependent ATP synthesis is the result of _____ phosphorylation. (A) oxidative； electron (B) proton-gradient； oxidative (C) substrate-level； oxidative (D) substrate-level； electron (E) oxidative； substrate-level

22. The reaction, ATP + AMP → 2ADP, is catalyzed by: (A) adenylatephosphorylase. (B) AMP-phosphotransferase. (C) ADP mutase. (D) adenylate kinase. (E) None are true.

24. Given the following saturated fatty acid, how many β-oxidation cycles does it require to completely metabolize the above fatty acid to acetyl-CoA? (A) 2. (B) 3. (C) 4. (D) 5. (E) 6.

複選題25. Ketone bodies are produced by the β-oxidation of an excess of acetyl-CoA. Which of the followings are ketone bodies? ①②③④⑤(A) ①②③ (B) ①②④ (C) ②③④ (D) ②③⑤ (E) ②④⑤

26. Peptide A has amino acid sequence "CKGHNLRYEKDSAI". 　 1. Sophia used trypsin to digest the peptide. She obtained a pentapeptide. The pI of this pentapeptide is higher than 10. 　 2. Peptide A does not contain any residue with two chiral centers. 　 3. Peptide A contain only one aromatic residue. 　 4. Peptide A does not contain any residue which could be phosphorylated. 　 5. Peptide A does not contain any residue which could be modified with N-linked glycan in glycoproteins. (A) 3, 5 are correct. (B) 1, 3 are correct. (C) 1, 3, 4 are correct. (D) 1, 4 are incorrect. (E) 2, 3 are correct.

複選題27. Please choose the   correct   answer(s) from the following descriptions: 　 1. A residue which has the dihedral angle shown below might be in an alpha-helix.  2. Glc(α1→4)Glc linkage appears in the most abundant homopolysaccharide in the world. 　 3. Phosphorylase releases glucose-1-P from the reducing end of amylopectin. 　 4. The peptide with the sequence "AFAKLWPIEACQA" does not contain any cleavage site for cyanogen bromide. 　　 5. The amino acid "Trp" has the highest extinction coefficient at UV280 nm. (A) 1, 3, 4 are correct. (B) Only 2 is incorrect.(C) 2, 5 are incorrect.(D) 1, 4, 5 are correct.  (E) Only 5 is correct. 

28. There are four proteins A, B, C, D. (Protein A: homotetramer, = 280,000, pI =6； Protein B: monomer, = 113,000, pI=7； Protein C: monomer, = 13,000, pI=8； Protein D is unknown). When Samuel used a gel filtration column to separate them, the elution sequence is A-D-B-C. Samuel dissolved the protein mixture in 20 mM phosphate buffer (pH 8) and loaded to a anion exchange column equilibrated with the same buffer. Protein D could not bind to this column. On an SDS-PAGE gel, protein D runs faster than protein B and slower than protein C. 1. If Samuel used SDS-PAGE to separate A, B, and C. The sequence of the protein bands shown in gel from top to bottom should be A-B-C. 　 2. The molecular mass of protein D must be between 13 and 113 kDa. 　 3. The pI of protein D might be higher than 8. 　 4. D is not a monomer. 　 5. If Samuel used 2-Dimensional electrophoresis to separate them. We could predict that the relative positions of these four proteins is like the image below.  (A) 1, 5 are correct. (D) 2, 4 are correct. (B) Only 2 is incorrect. (E) 3, 4 are correct. (C) 1, 3, 4 are correct.

29. The following data were obtained in a study of an enzyme known to follow Michaelis-Menten kinetics:  The for this enzyme is approximately:(A) 1 mM. (B) 2 mM. (C) 4 mM. (D) 6 mM. (E) 1000 mM.