30. The synthesis of purine and pyrimidine nucleotides differ in that:
(A) pyrimidine biosynthesis is
tightly regulated in the cell, whereas purine biosynthesis is not.
(B) ATP is required in the
synthesis of purines but not in the synthesis of pyrimidines.
(C) pyrimidines go through many
steps, adding a single carbon or nitrogen each time, whereas the basic skeleton for purines is
formed by two main precursors.
(D) purine formation requires a THF derivative, whereas
pyrimidine formation does not.
(E) purine biosynthesis starts with the formation of PRPP,
whereas pyrimidines incorporate the PRPP near the end of the pathway.

1. In biochemical metabolism, decarboxylation and carboxylation requires __________ and __________, respectively. (A) biotin, cobalamin. (B) pyridoxine, thiamine. (C) thiamine, cobalamin. (D) thiamine, biotin. (E) cobalamin, pyridoxine.

2. (A) Transaldolase, (B) Transketolase, (C) Glucose 6-phosphate dehydrogenase, (D) Phosphopentose isomerase, (E) Phosphopentose epimerase deficient will cause pamaquine -induced hemolytic anemia.

3. Which of the following statements about fatty acid metabolism is true? (A) Carnitine serves as a carrier to transport acetyl units from the mitochondrion to the cytosol for fatty acid synthesis. (B) Malonyl CoA is the two-carbon unit for fatty acid synthesis. (C) Decarboxylation initiates fatty acid degradation. (D) α - oxidation occurs in the endoplasmic reticulum of the liver and kidney and preferred 10 or 12 carbon fatty acids when  oxidation is defective. (E) ω - oxidation occurs in the peroxisomes and preferred a branched-fatty acid.

4. Among major human plasma lipoprotein classes, ____________ is the highest triacylglycerol content basis on dry weight, and ___________ is the principal form in which cholesterol is transported to tissues. (A) high density lipoprotein (HDL) chylomicron, (B) low density lipoprotein (LDL) intermediate density lipoprotein (IDL), (C) very low density lipoprotein (VLDL) chylomicron (D) chylomicron LDL, (E) IDL HDL.

5. In addition to pentose phosphate pathway, the source of NADPH for fatty acid biosynthesis is(A) Pyruvate dehydrogenase complex, (B) malate dehydrogenase, (C) citrate lyase,(D) malic enzyme, (E) 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) lyase.

6. Experiments that investigated the Pasteur effect showed that when oxygen is introduced to anaerobic yeast, where glycolysis is occurring, all intermediates beginning with ________ become depleted due to inhibition of the enzyme _________. (A) glucose-6-phosphate, hexokinase. (B) fructose-6-phosphate, phosphofructokinase. (C) fructose-1,6-bisphosphate, phosphofructokinase. (D) phosphoenolpyruvate, pyruvate kinase. (E) fructose-1,6-bisphosphate, fructose-1,6-bisphosphate aldolase.

7. Insulin can __________ phosphofructokinase 2, __________ pyruvate dehydrogenase complex, ______________ acetyl CoA carboxylase, and _____________ lipase to regulate glucose and lipid metabolism in animal cells. (A) active, active, active, active. (B) inactive, inactive, inactive, inactive. (C) active, active, active, inactive. (D) inactive, active, inactive, active. (E) active, inactive, active, inactive.

8. Which of the following compounds are the inhibitors of gluconeogenesis？1. ATP, 2. AMP, 3. acetyl CoA, 4. citrate, 5. glucose 6-phosphate, 6. fructose 2,6-bisphosphate.(A) 1 and 5. (B) 2 and 6. (C) 1 and 4. (D) 3 and 5. (E) 3 and 6.

9. Which of the following statements is not true? (1) In muscle, the activity of phosphofructokinase is regulated by pH value. (2) Lactase deficiency cause many adults are intolerant of milk. (3) In vertebrate liver, fructokinase is bypassed during fructose metabolism, often leading to conversion of excess fructose into fat. (4) Ethanol is metabolized in the cytosol of liver that will elevate the [NADH]/[NAD+ ] ratio, and inhibit glycolysis and gluconeogenesis. (5) Compared to hexokinase, glucokinase displays sigmoidal kinetics for glucose uptake and higher glucose affinity. (A) 1 and 3, (B) 2 and 4, (C) 3 and 5, (D) only 3, (E) only 5.

10. Which of following statements is false? (A) Ionophores can destroy the electrochemical gradients in the living cells. (B) The Na+ -K + pump acts in all cells to maintain lower concentrations of K+ inside and Na+ outside. (C) Tetrodotoxin is found in some organs of the puffer fish and has a good affinity and inhibitor for sodium channel. (D) Cobratoxin and -bungarotoxin have high affinity with acetylcholine receptor. (E) Acetylcholine binds to its receptor in the postsynaptic membrane opens Na+ channel and depolarization the postsynaptic membrane, generating a new action potential.

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