25. For each molecule of acetyl-CoA that enters the citric acid cycle, which of the following sets represents the net products of the cycle?
(A) 2 CO₂, 2 NADH, 2 FADH₂, 1 GTP, 1 oxaloacetate
(B) 2 CO₂, 3 NADH, 1 FADH₂, 2 GTP, 1 oxaloacetate
(C) 2 CO₂, 2 NADH, 1 FADH₂, 2 GTP, 0 oxaloacetate
(D) 2 CO₂, 3 NADH, 1 FADH₂, 1 GTP, 1 oxaloacetate
(E) 2 CO₂, 3 NADH, 1 FADH₂, 1 GTP, 0 oxaloacetate

21. Which type of damage to DNA structure is most likely to be caused by UV light? (A) Deamination (B) Pyrimidine dimers (C) Depurination (D) Depyrimidination (E) Hydrolysis of the phosphodiester bond

22. Which compound is an intermediate of the β-oxidation of fatty acids? (A) CH3—(CH2)20—CO—COOH (B) CH3—CH2—CO—CH2—CO— OPO32– (C) CH3—CH2—CO—CH2—OH (D) CH3—CH2—CO—CO—S—CoA (E) CH3—CO—CH—CO—S—CoA

23. Which of the following enzymes requires coenzyme B1 as cofactor? (A) Pyruvate decarboxylase (B) Malic enzyme (C) Alcohol dehydrogenase (D) Citrate synthase (E) Pyruvate carboxylase

24. Which of the following statements is not correct? (A) Bacterial peptidoglycan contains (β1→4) glycosidic linkage. (B) Cellulose contains (β1→4) glycosidic linkage. (C) Starch contains (α1→6) glycosidic linkage. (D) Glycogen contains (α1→4) glycosidic linkage. (E) Lactose contains (α1→4) glycosidic linkage.

26. Fatty acids are activated to acyl-CoA, however, why the acyl group is further transferred to carnitine for β-oxidation? (A) Carnitine is required to oxidize NAD+ to NADH. (B) Acyl- CoAs easily cross the mitochondrial membrane, but the fatty acids themselves will not. (C) Acyl-carnitines readily cross the mitochondrial inner membrane, but acyl-CoAs do not. (D) Fatty acids cannot be oxidized by FAD unless they are in the acyl-carnitine form. (E) Carnitine can be oxidized to provide additional energy in mitochondria.

27. Which of the following is the building block for the biosynthesis of phenylalanine, tyrosine, and tryptophan? (A) Pyruvate (B) Phosphoenolpyruvate (C) Acetyl-CoA (D) α-Ketoglutarate (E) Ribose-5-phosphate

28. The reactions of citric acid cycle where CO2 is produced are catalyzed by ________ and ________, respectively. (A) Isocitrate dehydrogenase; Malate dehydrogenase (B) Isocitrate dehydrogenase; α-ketoglutarate dehydrogenase (C) α-ketoglutarate dehydrogenase; Succinate dehydrogenase (D) α-ketoglutarate dehydrogenase; Malate dehydrogenase (E) Succinate dehydrogenase; Malate dehydrogenase

29. Which of the following is false regarding the oxidation of 1 mole of palmitate (16:0) by the β-oxidation pathway? (A) 1 mole of ATP is needed. (B) 8 moles of acetyl-CoA are formed. (C) 8 moles of FADH2 are formed. (D) AMP and PPi are formed. (E) The reactions occur in the mitochondria.

30. What is the source of the polar head group in the formation of sphingomyelin? (A) CDP-choline (B) Phosphocholine (C) Cardiolipin (D) Phosphoserine (E) Phosphatidylcholine

31. Which one of the following is one kind of interspecific interaction along a food chain? (A) Competition (B) Predation (C) Parasitism (D) Mutualism (E) Positive interaction