15. Which one of the following statements about mRNA stability is true?
(A) Degradation always proceeds in the 5' to 3' direction.
(B) Degradation of mRNA by polynucleotide phosphorylase yields 5'-nucleoside monophosphates.
(C) In general, bacterial mRNAs have longer half-lives than do eukaryotic mRNAs.
(D) Rates of mRNA degradation are always at least ten-fold slower than rates of mRNA synthesis.

(E) Secondary structure in mRNA (hairpins, for example) slows the rate of degradation.

1. Aside from maintaining the integrity of its hereditary material, the most important general metabolic concern of a cell is: (A) keeping its glucose levels high. (B) maintaining a constant supply and concentration of ATP. (C) preserving its ability to carry out oxidative phosphorylation. (D) protecting its enzymes from rapid degradation. (E) running all its major metabolic pathways at maximum efficiency.

2. A function of the glyoxylate cycle, in conjunction with the citric acid cycle, is to accomplish the: (A) complete oxidation of acetyl-CoA to CO2 plus reduced coenzymes. (B) net conversion of lipid to carbohydrate. (C) net synthesis of four-carbon dicarboxylic acids from acetyl-CoA. (D) net synthesis of long-chain fatty acids from citric acid cycle intermediates. (E) Both B and C are correct

3. The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields_______mol of NADH,_______mol of FADH2, and______mol of ATP (or GTP). (A) 2; 2; 2 (B) 3; 1; 1 (C) 3; 2; 0 (D) 4; 1; 1 (E) 4; 2; 1

4. The conversion of palmitoyl-CoA (16:0) to myristoyl-CoA (14:0) and 1 mol of acetyl-CoA by the ẞ-oxidation pathway results in the net formation of: (A) 1 FADH, and 1 NADH. (B) 1 FADH, and 1 NADPH. (C) 1 FADH2, 1 NADH, and 1 ATP. (D) 2 FADH, and 2 NADH. (E) 2 FADH2, 2 NADH, and 1 ATP.

5. If an aerobic organism (for example, the bacterium E. coli) were fed each of the following four compounds as a source of energy, the energy yield per mole from these molecules would be in the order: (A) alanine ＞ glucose ＞ palmitate (16:0). (B) glucose ＞ alanine ＞ palmitate. (C) glucose palmitate ＞ alanine. (D) palmitate ＞ alanine ＞ glucose. (E) palmitate ＞ glucose ＞ alanine.

6. In amino acid catabolism, the first reaction for many amino acids is a(n): (A) decarboxylation requiring thiamine pyrophosphate (TPP). (B) hydroxylation requiring NADPH and O2. (C) oxidative deamination requiring NAD+. (D) reduction requiring pyridoxal phosphate (PLP). (E) transamination requiring pyridoxal phosphate (PLP).

7. Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:(A) oxaloacetate.(B) propionate.(C) pyruvate.(D) succinate.(E) succinyl-CoA.

8. Which one of the following statements about photophosphorylation is false? (A) It can be uncoupled from electron flow by agents that dissipate the proton gradient. (B) The difference in pH between the luminal and stromal side of the thylakoid membrane is 3 pH units. (C) The luminal side of the thylakoid membrane has a higher pH than the stromal side. (D) The number of ATPs formed per oxygen molecule is about three. (E) The reaction centers, electron carriers, and ATP-forming enzymes are located in the thylakoid membrane.

9. The relative concentrations of ATP and ADP control the cellular rates of:(A) glycolysis.(B) oxidative phosphorylation.(C) pyruvate oxidation.(D) the citric acid cycle.(E) all of the above.

10. In the carbon assimilation ("dark") reactions of photosynthesis, the biosynthesis of 1 mol of hexose from 6 mol of carbon dioxide requires: (A) 12 mol of NADPH and 12 mol of ATP. (B) 12 mol of NADPH and 18 mol of ATP. (C) 18 mol of NADPH and 12 mol of ATP. (D) 18 mol of NADPH and 18 mol of ATP. (E) no NADPH and 12 mol of ATP.

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