12. Which is a characteristic of sphingolipids?
(A) They all contain a fatty acid joined to glycerol.
(B) They all contain a long-chain alcohol joined to isoprene.
(C) They all contain ceramide joined to a polar group.
(D) They all contain a carbohydrate joined to a phosphate group.
(E) They all contain a polar head group and two non-polar fatty acids.

8. What is the purpose of using reverse transcriptase in DNA-based technologies? (A) To transcribe RNA into DNA. (B) To replicate DNA. (C) To cut DNA at specific sites.  (D) To ligate DNA fragments. (E) To amplify proteins.

9. CRISPR-Cas9 technology is used for: (A) DNA amplification. (B) gene silencing. (D) protein synthesis. (E) DNA repair.(C) gene editing.

10. Which of the following statements concerning receptor enzymes is correct? (A) They are not usually membrane-associated proteins. (B) They contain an enzyme activity that acts upon a cytosolic substrate. (C) They contain an enzyme activity that acts upon the extracellular ligand. (D) They have a ligand-binding site on the cytosolic side of the membrane. (E) They have an active site on the extracellular side of the membrane.

11. The E. coli recombinant plasmid pBR322 has been widely utilized in genetic engineering experiments. pBR322 has all of the following features except: (A) A number of conveniently located recognition sites for restriction enzymes. (B) A replication origin, which permits it to replicate autonomously. (C) Resistance to antibiotics, which permits rapid screening for recombinant plasmids containing foreign DNA. (D) Small overall size, which facilitates entry of the plasmid into host cells. (E) A number of palindromic sequences near the EcoRI site, which permit the plasmid to assume a conformation that protects newly inserted DNA from nuclease degradation.

13. Which of these statements about triacylglycerol synthesis is correct? (A) Humans can store more energy in glycogen than in triacylglycerols. (B) Insulin stimulates conversion of dietary carbobydrate into triacylglycerols. (C) Triacylglycerols are the building blocks for cell membrane architecture. (D) Mammals are unable to convert carbohydrates into triacylglycerols. (E) Phosphatidic acid is not on the pathway of triacylglycerol synthesis.

14.What are the products of β oxidation of a saturated 20-carbon fatty acid? (A) 1 propionyl-CoA, 9 acetyl-CoA, 9 FADH2, and 9 NADH (B) 9 acetyl-CoA, 8 FADH2,8 NADH (C) 9 acetyl-CoA, 9 FADH2,9 NADH (D) 10 acetyl-CoA, 9 FADH2, 9 NADH (E) 10 acetyl-CoA, 10 FADH2, 10 NADH

15. For skeletal muscle, which of the following correctly pairs the activity state with the source of energy? (A) resting: glucose (B) resting: amino acids (C) exertion: glucose (D) exertion: fatty acids (E) None of the above.

16. Which of the following is true of glucagon? (A) It is released from the pancreatic β-cells when glucose levels are low. (B) Its synthesis and release are exclusively under the control of epinephrine. (C) The primary targets of glucagon are liver, adipose and muscle tissues. (D) Major pathways promoted by glucagon include glycogenolysis and glycolysis. (E) None of the above.

17. Oxidation-reduction reactions in biological system always involve； (A) direct participation of oxygen. (B) transfer of electron(s). (C) mitochondria. (D) formation of water. (E) transfer of hydrogens.

18. Carotenoids have primary roles in photosynthesis as: (A) accessory light-harvesting and photooxidation. (B) accessory light-harvesting and photoprotection from reactive oxygen species. (C) resonance transfer pigments and photooxidation. (D) resonance transfer and photodiffusion protection. (E) None are true.