Answer questions about the following molecule. 1. Which of the following stateme
ID: 1072846 • Letter: A
Question
Answer questions about the following molecule.
1. Which of the following statements about cholesterol is not correct?
(a) Cholesterol is a steroid that contains a tetracyclic ring system.
(b) Cholesterol is a steroid that contains 8 chiral carbons and can form 28 or 256 stereoisomers.
(c) Each atom or group attached to a ring-junction carbon (i.e., carbons a –e) is in a trans or axial position. Because of this the tetracyclic ring system is mostly flat.
(d) Cholesterol is used to synthesized vitamin D, bile acids, sex hormones, and adrenocorticoid hormones.
(e) Cholesterol is not found in the cell membranes of animals.
2. Which of the following statements about cholesterol is not correct?
(a) LDLs (low-density lipoproteins) transport cholesterol from the liver to tissues and cells.
(b) HDLs (high-density lipoproteins) transport unused cholesterol from the tissues and cells back to the liver where it is degraded to bile acids and excreted in feces.
(c) HDLs promote atherosclerotic deposits in blood vessels but LDLs reduce such risks.
(d) Cholesterol is insoluble in blood plasma unless complexed to lipoproteins.
(e) Cholesterol is synthesized in the liver, therefore plants do not synthesize cholesterol.
HO CH Cholesterol CH3Explanation / Answer
1(d) is incorrect because cholesterol composes about 30% of all animal cell membranes which is required to build and maintain membranes and modulates membrane fluidity.
2 (c) is incorrect because HDL cholesterol is considered “good” cholesterol because it helps remove LDL cholesterol from the arteries whereas LDL cholesterol is considered the “bad” cholesterol because it contributes to plaque, a thick, hard deposit that can clog arteries and make them less flexible. This condition is known as atherosclerosis