18. Which of the following statements about lipoproteins is INCORRECT?
(A) High density lipoproteins (HDL) absorbs cholesterol and carries it back to the liver.
(B) Chylomicrons are mainly composed of cholesterol absorbed from the gut.
(C) Very low density lipoprotein (VLDL) are large triglyceride-rich lipoproteins produced in liver.
(D) Low density lipoproteins (LDL) are the main transporters of cholesterol in the blood, carry cholesterol from the liver to cells throughout the body.
(E) Intermediate density lipoproteins (IDL) are derived from VLDL after removal of triacylglycerol.

14. Which one of the following descriptions is WRONG? (A) Caffeine is a trimethylxanthine. (B) Theophylline is a dimethylxanthine. (C) Theobromine is the bypoxanthine derivative of cocoa. (D) Theobromine and theophylline are similar but lack the methyl group at N-1 and at N-7, respectively.

15. Which one of the following subunits is NOT contained in the basic DNA-dependent RNA polymerase of the bacterium Escherichia coli? (A) α subunit (B) β subunit (C) ω subunit (D) σ subunit

16. Which of the following descriptions about apolipoproteins is CORRECT? (A) Apo A-I is the ligand for LDL receptor, while Apo B-100 binds to HDL receptor. (B) Nascent VLDL and nascent chylomicron both contain Apo C and E. (C) Apo C-II serves as the enzyme cofactor of lipoprotein lipase. (D) Apo B-48 on VLDL and Apo B-100 on LDL were encoded from two different genes, and the peptide sequence homology are about 70%. (E) Apo B-100 contains LDL receptor binding domain, but Apo-E cannot bind to LDL receptor.

17. Which of the following descriptions about acylglycerol and sphingolipid synthesis is CORRECT? (A) In adipose tissue, glycerol 3-phosphate is synthesized by the phosphorylation of glycerol. (B) Glycerol 3-phosphate is phosphorylated by glycerol kinase, and there is no alternative synthesis pathway from glycolysis. (C) Glycerol 3-phosphate acyltransferase is the rate limiting step of triacylglycerol synthesis. (D) Phosphatidylcholine synthesis involve ADP-activated choline. (E) All sphingolipids are formed from ceremide.

19. Seahorse XFe analyzer is designed to measure oxygen consumption rate. Which of the following drug can be added to measure the maximum oxygen consumption rate of cells to estimate the maximal mitochondrial function? (A) High concentration of glucose. (B) Substrate of Isocitrate dehydrogenase, Isocitrate. (C) CarbonyI cyanide-p-trifluoromethoxyphenyIhydrazone (FCCP): uncouplers which disrupt the permeability of the inner membrane. (D) High concentration of pyruvate. (E) Antimycin A: complex Ill inhibitor.

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.

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