25. Which enzyme is deficient in phenylketonuria?
(A) Phenylalanine hydroxylase.
(B) Tyrosine hydroxylase.
(C) Phenylalanine transaminase.
(D) Phenylalanine deaminase.
(E) Tyrosine kinase. 

21. Which of the following statements correctly describes the roles of insulin and glucagon in glucose homeostasis? (A) Insulin promotes glycogenolysis and gluconeogenesis in the liver, while glucagon promotes glycolysis and glycogenesis. (B) Insulin stimulates glucose uptake in muscle and adipose tissues by upregulating GLUT4 transporters, whereas glucagon primarily acts on the liver to increase glucose production. (C) Insulin inhibits lipogenesis and enhances β-oxidation of fatty acids, whereas glucagon stimulates lipogenesis and inhibits β-oxidation. (D) Both insulin and glucagon act through receptor tyrosine kinases to mediate their effects on target tissues. (E) Insulin and glucagon are secreted by pancreatic β-cells in response to high glucose levels.

22. Which of the following statements about oncogenes and tumor suppressor genes is INCORRECT? (A) Oncogenes are typically derived from proto-oncogenes through activating mutations, which lead to a gain of function and promote uncontrolled cell proliferation. (B) Tumor suppressor genes usually require both alleles to be inactivated by mutations or deletions to lose their function, a concept described by the "two-hit hypothesis." (C) Mutations in oncogenes are often dominant, while mutations in tumor suppressor genes are typically recessive. (D) Oncogenes are involved in processes such as apoptosis and DNA repair, whereas tumor suppressor genes primarily regulate growth and cell division. (E) The p53 protein, a tumor suppressor, plays a key role in the DNA damage response by inducing cell cycle arrest or apoptosis.

23. Which of the following hormones or neurotransmitters is NOT derived from an amino acid? (A) Serotonin. (B) Thyroxine (T4). (C) Dopamine. (D) Testosterone. (E) Epinephrine.

24. Which of the following organelles plays a crucial role in the modification and sorting of secretory proteins? (A) Endoplasmic reticulum. (B) Lysosome. (C) Autophagosome. (D) Golgi apparatus. (E) Peroxisome.

1. Which of the following statements is correct regarding acetyl-CoA carboxylase? (A) Acetyl-CoA carboxylase is an allosteric enzyme. (B) Acetyl-CoA carboxylase is regulated by hormones via changes in its phosphorylation state. (C) Acetyl-CoA carboxylase is the most important enzyme in the regulation of lipogenesis. (D) All of the above are correct

2. Which of the following statements is wrong regarding the regulation of acetyl-CoA carboxylase? (A) Citrate promotes the conversion of the enzyme from an inactive dimer to an active polymeric form (B) Long-chain acyl-CoA promotes inactivation of the enzyme by phosphorylation of the enzyme. (C) Long-chain acyl-CoA promotes the tricarboxylate transporter, which transports citrate out of mitochondria into the cytosol. (D) All of the above are correct

3. Which of the following nucleotide triphosphates is the structure above?  (A) CTP (B) ATP (C) dATP (D) dCTP

5. Based on the table above, which of the following DNA sequences corresponds to the potential coding region for this peptide? (表格請見試卷) (A) ATG CCT TAC GAT GTG CCT GAT TAT GCT (B) TAA CCC TAT GAT GTA CCC GAC TAC GCC (C) TAT CCA TAA GAC GTC CCA GAT TAT GCA (D) TAC CCG TAT GAC GTC CCG GAC TAC GCG

7. To further characterize the viral protein, a synthetic DNA probe with 18 nucleotides was used to screen cDNA libraries prepared from viral infected serum. According to the table above, which of the following peptides will minimize the number of DNA probes for the screening?  (A) YPYDVP (B) PYDVPD (C) YDVPDY (D) DVPDYA

8. Which of the following descriptions of carnitine palmitoyltransferase-I is correct? (A) The enzyme is located in the inner mitochondrial membrane. (B) The enzyme transfers the long-chain acyl group from CoA to carnitine, forming acylcarnitine and releasing CoA. (C) The enzyme also binds acylcarnitine and transports it across the membrane in exchange for carnitine. (D) All of the above are correct.