Question

12. Which of the following best describes the components of phospholipids? A) Glycerol, one fatty acid, two phosphate groups and an aminoalcohol B) Glycerol, two fatty acids, one phosphate group, and an aminoalcohol C) Sphingosine, two fatty acid, one phosphate group and an aminoalcohol D) Glycerol, three fatty acids, and a phosphate group 13. When ribose adopts the most stable cyclic structure hemiacetal, which of the following is happening? A. it becomes a furonose C. an acetal is formed B. C-1 and C-5 atoms are connected by an oxygen atom D. a racemic mixture, 50% beta anomer 150% alpha anomer is formed 14. The compound shown is which? ное A Ribose B D -ketose CD-Aldose D. Galactose E. An epimer of glucose CHOH 15. The common precursor of prostaglandins, thromboxines and leukotrienes is A. Cholesterol B. Arachidonic acid C Progesterone D. Estradiol 16. Prostaglandins are A. Bile salts important for digestion of fats B Sex hormones C Emulsifying agents D. Membrane components E. Inflammatory agents 17. Heating a fat with water and which of these reagents will make a soap? A HCI B. H SOC. HNO D.CaCl E. NaOH 18. Which of the following defines all lipids? A) The presence of a specific functional group The number of cyclohexane rings in it Their insolubility in water D) Their content of phosphate 19. All steroids contain at least how many rings? Al B.2 C.3 D. 4 E.S . 20. Unsaturated lipids are converted to saturated fatty acids by which one of the following processes A. Dehydration B. Hydrogenation C. Saponification D. Hydration

Answer 1

12. Option B.

Phospholipids are known to be made up of two fatty acids, one glycerol and one phosphate group. Usually phosphate groups also contain amino alcohols for example hydroxy group containing amino acid like serine, or ethanol amines scuh as choline. fatty acid groups render hydrophobicity to the phospholipids while phosphate groups constitute hydrophilic portion. They impart amphiphilic character to phsophlipids and glycerol helps to join these hydrophobic and hydrophilic portions.

13. Option B

Formation of hemiacetals or acetals occur through the reaction between oxygen atom of alcohol and carbonylgroup of either aldehyde or ketone. This can occur both intermolecular and intramolecular pathways. In case of ribose, the formation of intramolecular hemiacetal happens through oxygen bond connecting C1 and C5 carbons. Six membered pyranose rings are formed in favor to 5 membered furansoe ring.

14. Option B.

The given structure contains ketone functional group suggesting that it belongs to D-ketose group.

Aldose gerally contain aldehyde functional group hich is absent in given structure, while ribose has both hydroxyl and aldehyde groups.

15. Option B

Arachidonic acid is precursor fro prostaglandins and thromboxanes arealso related to prostaglndins.