Lesson 19. Cholesterol and Lipoproteins I 1. a. b. c. d.
What is incorrect about the structure of cholesterol? Steroid with four hydrocarbon rings (3 w/ 6C + 1 w/ 5C) Amphipathic (hydroxyl group near polar heads + most of molecule near fatty acid chains) Single polar hydroxyl group No double bond or hydrocarbon tail
1. A: Cholesterol has a hydrocarbon tail, single polar OH, methyl group, and double bond. It is a steroid w/ 4 rings and the OH makes it amphipathic. 2. Where is cholesterol biosynthesis least likely to occur? a. Liver b. Intestine c. Adrenal cortex d. Reproductive tissue e. Adrenal medulla 2. E: The largest production of cholesterol is in the liver, intestine, adrenal cortex, and reproductive tissue. 3. What is true about cholesterol biosynthesis? a. Some carbons are derived from acetyl-CoA b. NADPH is the reducing agent c. Hydrolysis of acetyl CoA and GTP drives the endergonic process d. Synthesis begins in the ER and finishes in the cytosol 3. B: NADPH not NADH is the reducing agent. All carbons are derived from acteyl-CoA. Hydrolysis of acetyl CoA and ATP (not GTP) drives the endergonic (not exergonic) process. Synthesis begins in the cytoplasm and ends in the ER. 4. Place the 6 molecules of cholesterol biosynthesis in order: I. Acetyl CoA II. Mevalonate III. Squalene IV. Isopentenyl pyrophosphate (IPP) V. Lanosterol VI. Cholesterol a.I, II, III, IV, V, VI b.I, II, IV, III, V, VI c. I, II, III, V, IV, VI d. I, II, IV, V, III, VI 4. B: Cytoplasm: Acetyl CoA -> Mevalonate -> IPP ER: IPP -> Squalene -> Lanosterol -> Cholesterol