24. Which of the following nucleotide serves as a key second messenger in signaling pathway?
(A)
(B)
(C)
(D)
(E)

20. Which of the following statements is NOT one of the major metabolic functions of liver? (A) Bile production to facilitate lipid digestion and absorption. (B) Both synthesis and oxidation of fatty acids. (C) Synthesis of triacylglycerols and phospholipids. (D) Conversion of ketone bodies into acetyl-CoA, which then enters the Krebs cycle and be oxidized for energy production. (E) Both synthesis and metabolism of plasma lipoproteins.

21. Which of the following descriptions about cholesterol synthesis and metabolism is CORRECT? (A) The rate limiting step of cholesterol synthesis is regulated by HMG-CoA synthase. (B) Cholesterol transported with lipoprotein in the blood circulation are mostly as free form cholesterol, while the cholesterol stored in adipose tissue are esterified by long chain fatty acids. (C) Insulin activates HMG-CoA reductase by promoting its dephosphorylation. (D) Monoclonal antibody against proprotein convertase subtilisin/kexin 9 (PCSK9) lowers serum LDL cholesterol by enhancing the degradation of the LDL receptor. (E) Increased amount of cholesterol activates transcription factor sterol regulatory element-binding protein (SREBP) to increase HMGCR (Gene of HMG-CoA reductase) mRNA transcription.

22. Which of the following description about nucleic acid is INCORRECT? (A) DNA synthesis involves a more intricate and precise proofreading, the DNA repair mechanisms are preserved among all organisms. (B) The initiation steps of DNA and RNA synthesis both require RNA primers. (C) During RNA replication, only a portion of the genome is synthesized, whereas during DNA replication, the entire genome is synthesized. (D) Many short fragments, called "Okazaki fragments", formed on the lagging strand of DNA synthesis. (E) Mitochondrial DNA is circular, which is structurally similar to bacterial DNA.

23. Which of the following description purine and pyrimidine de novo synthesis INCORRECT? (A) The initial reaction of purine biosynthesis is forming phosphoribosyl pyrophosphate (PRPP). (B) Both adenosine monophosphate (AMP) and guanosine monophosphate (GMP) can be derived from inosine monophosphate (IMP). (C) The so-called orotate pathway of pyrimidine de novo synthesis involves using PRPP serves as a scaffold for the subsequent assembly of the pyrimidine ring to form uridine 5'-monophosphate (UMP). (D) Thymidylate synthase is the sole enzyme responsible for de novo biosynthesis of thymidine monophosphate (TMP). (E) Cross-regulation exists between purine and pyrimidine biosynthesis, suggesting coordinated control of their biosynthesis.

25. Which of the following is a nucleotide, which is composed of a nitrogenous base, a pentose sugar and a phosphate? (A) Adenine (B) Guanylate (C) Thymidine (D) Deoxycytidine

26. In each of the following pairs of amino acids, identify which amino acid would be most soluble in water: (A) Glu, Ile (B) Tyr, Phe (C) Ser, Ala (D) Trp, His

30. Which peptide has greater absorbance at 280 nm ? (A) Ser-Val-Trp-Asp-Phe-Gly-Tyr-Trp-Ala (B) Gin-Leu-Glu-Phe-Thr-Leu-Asp-Gly-Tyr (C) Asp-Tle-Asn-Pro-Thr-Arg-Asp-Val-Phe (D) Asn-Phe-Gln-Met-Thr-Leu-Tyr-Lys-Tyr

1.Identify the components that is/are NOT a part of DNA. (A) Ribose (B) Base A, T, C, G (C) 5'-phosphate group (D) 3'-hydroxyl group (E) Deoxyribose

2.DNA is a structurally dynamic molecule that can exist in a variety of helical forms. Which of the following is/are NOT a known DNA structure? (A) A-DNA (B) B-DNA (C) , C-DNA (D) X-DNA (E) Z-DNA

複選題3. Which of the following enzymes is/are required for DNA replication? (A) Helicase (B) Topoisomerase (C) DNA polymerase (D) DNA ligase (E) Recombinase