Download 生物化學小考(一) 範圍ch1~ch4

生物化學小考(五)
範圍 ch17~ch21
單選題(每題 2 分, 總分 20 分)
1. One amino acid directly involved in the purine biosynthetic pathway is:
(A) alanine.
(B) aspartate.
(C) glutamate.
(D) leucine.
(E) tryptophan
2. The ribosyl phosphate moiety needed for the synthesis of orotidylate, inosinate, and guanylate is
provided most directly by:
(A) 5-phosphoribosyl 1-pyrophosphate.
(B) adenosine 5'-phosphate.
(C) guanosine
5'-phosphate. (D) ribose 5-phosphate.
(E) ribulose 5-phosphate.
3. A cell that is unable to synthesize or obtain tetrahydrofolic acid (H4 folate) would probably be
deficient in the biosynthesis of:
(A) CMP.
(B) dCMP.
(C) orotate.
(D) thymidylate (TMP).
(E) UMP.
4. Which of the following is not true of the reaction catalyzed by ribonucleotide reductase?
(A) Glutathione is part of the path of electron transfer.
(B) It acts on nucleoside diphosphates.
(C) Its mechanism involves formation of a free radical.
(D) There is a separate enzyme for each nucleotide (ADP, CDP, GDP, UDP).
(E) Thioredoxin acts as an essential electron carrier.
5. If the free energy change △G for a reaction is -46.11 kJ/mol, the reaction is:
(A) at equilibrium.
(B) endergonic.
(C) endothermic.
6. The major carrier of chemical energy in all cells is:
(A) acetyl triphosphate.
(B) adenosine monophosphate.
cytosine tetraphosphate.
(E) uridine diphosphate.
(D) exergonic.
(E) exothermic.
(C) adenosine triphosphate.
(D)
7. Which of these statements about nucleic acids is false?
(A) Mitochondria and chloroplasts contain DNA.
(B) Plasmids are genes that encode plasma proteins in mammals.
(C) The chromosome of E. coli is a closed-circular, double-helical DNA.
(D) The DNA of viruses is usually much longer than the viral particle itself.
(E) The genome of many plant viruses is RNA.
8. Precursors for the biosynthesis of the pyrimidine ring system include:
(A) carbamoyl phosphate and aspartate.
(B) glutamate, NH3, and CO2.
(C) glycine and
succinyl-CoA. (D) glycine, glutamine, CO2, and aspartate.
(E) inosine and aspartate.
9. An intermediate of purine degradation in humans is:
(A) glutamate.
(B) NH4+.
(C) succinate.
(D) urea.
(E) uric acid.
10. Which of the following is not known to be involved in the process of assisted folding of
proteins?
(A) Chaperonins
(B) Disulfide interchange
(C) Heat shock proteins
(D) Peptide bond
hydrolysis
(E) Peptide bond isomerization