Cholesterol-chemistry and metabolism- Multiple choice questions

1)- Cholesterol is a precursor of all of the followings except-

a) Taurocholate

b) Glycocholate

c) Calcitriol

d) Corticosteroids

e) Calcitonin.

2)- All 27 carbon atoms of cholesterol are derived from-

a) Acetyl co A

b) Acetoacetyl co A

c) Propionyl co A

d) Succinyl co A

e) Malonyl co A

3)- Cytosolic  3-hydroxy-3-methylglutaryl CoA (HMG CoA) is reduced to Mevalonate for the synthesis of cholesterol, the enzyme catalyzing this irreversible step is-

a) Thiolase

b) Thioesterase

c) Thiophorase

d) HMG Co-A synthase

e) HMG Co-A reductase.

4)- Which out of the following statement best describes ACAT (Acyl co A cholesterol acyltransferase)?

a) Required for reverse cholesterol transport

b) Rate limiting enzyme for bile acid synthesis

c) Requires monounsaturated fatty acid for esterification of cholesterol

d) Required for degradation of chylomicrons and VLDL

e) It is a major component of HDL.

5)- Which out of the following statement is incorrect about bile salts?

a) The major constituent of bile

b) Solubilize dietary lipids

c) Major breakdown products of cholesterol

d) Taurocholate is the major bile salt.

e) Bile salts are highly effective detergents

6)-A deficiency of apoprotein C-ll results in the disease hyperlipoproteinemia type I in which there is a significant increase in the concentration of plasma triacylglycerol. Which of the following is true about the condition?

a) VLDL and HDL increase

b) Plasma appears milky

c) There is a risk of premature IHD

d) Serum total cholesterol increases

e) Apo C-II acts as an activator of the LCAT enzyme.

7)- Which of the following lipid-lowering drugs act by inhibiting the absorption of dietary cholesterol?

a) Statins

b) Ezetimibe

c) Colestipol

d) Clofibrate

e) Cholestyramine

8)- In familial hypercholesterolemia, cholesterol is deposited in various tissues because of the high concentration of LDL cholesterol in the plasma. Of particular concern is the oxidation of the excess blood LDL to form oxidized LDL (oxLDL). The oxLDL is taken up by immune-system cells called macrophages, which become engorged to form foam cells. Which statement best describes the formation of foam cells?

a) LDL receptors on peripheral cells are upregulated

b) LDL receptors for modified LDL (Ox LDL) are not down-regulated

c) LDL enters by pinocytosis to form foam cells

d) There is increased de no synthesis of cholesterol

e) Cholesterol is not extracted from macrophages by HDL

9)-A patient presents with very high levels of serum cholesterol. After a series of tests, it is concluded that the patient has high circulating levels of LDL cholesterol, but has normal levels of the liver LDL receptor. One possible explanation for this observation is which of the following?

a) The patient has a mutated form of apoprotein B-100.

b) The inability to selectively remove cholesterol from the LDL complex.

c) The absence of the enzyme lipoprotein lipase.

d) Decreased levels of acyl-CoA: cholesterol acyltransferase.

e) Altered phosphorylation of the LDL receptor.

10) A patient presents in your office with very high levels of serum cholesterol. He states that he has tried to follow the diet and exercise regimen you gave him last year. You decide that this patient would benefit from a drug such as Lipitor (atorvastatin). This class of drugs is effective in treating hypercholesterolemia because it has what effect?

a) Stimulates phosphorylation of the β-hydroxy-β-methyl glutaryl- CoA reductase enzyme

b)- Decreases the stability of the β-hydroxy-β-methyl glutaryl-CoA reductase protein

c)-Binds cholesterol preventing it from being absorbed by the intestine

d)- Directly prevents the deposition of cholesterol on artery walls

e)- Inhibits the enzyme β-hydroxy-β-methyl glutaryl-CoA reductase.

11)-Free cholesterol can affect cholesterol metabolism in the body by inhibiting cholesterol biosynthesis. The step at which free cholesterol inhibits its biosynthesis is by inhibiting which of the following processes?

a) Cyclizing of squalene to form lanosterol

b) Reduction of 7-dehydrocholesterol to form cholesterol

c) Formation of mevalonate from hydroxymethylglutaryl-CoA

d) Kinase that phosphorylates hydroxymethylglutaryl-CoA reductase

e) Condensation of acetyl-CoA and acetoacetyl-CoA to form hydroxymethyl glutaryl-CoA

12) A patient with hereditary type I hyperlipidemia presents with elevated levels of chylomicrons and VLDL triglycerides in the blood. The main function of the chylomicrons in circulation is to do which of the following?

a) Transport lipids from the liver

b) Transport dietary lipids from the intestine to target tissues

c) Transport cholesterol from IDL to LDL

d) Act as a receptor for triacylglycerols in the liver

e) Bind cholesterol esters exclusively

13) The modification to bile salts that increases the working pH range and amphipathic nature of bile salts is

a) 7α-Hydroxylation

b) Dehydroxylation by intestinal bacteria

c) Esterification

d) Conjugation to taurine or glycine

e) Formation of salts with sodium and Potassium.

14)- A 53-year-old male patient with elevated levels of low-density lipoprotein (LDL) cholesterol, signs of premature cholesterol gallstone disease and substantially elevated triglycerides visited his physician for a follow-up to check his current status. The patient had received various statin, HMG-CoA-reductase inhibitors therapies for the past 2 years. However, after blood work done at this follow-up visit, complications had still not subsided. This patient has similar problems as two of his siblings.

Which of the following best explains this patient’s dyslipidemia?

a) An influx of abnormal phospholipids in the gallbladder as a result of ileal disease

b) A loss of HMG-CoA reductase function

c) A loss of CYP7A1 (cholesterol 7α-hydroxylase) function

d) Elevated levels of ACAT

e) Less number of LDL receptors

15)-A patient has been on combination statin and Cholestyramine therapy to lower his serum cholesterol levels. Prior to any surgery, this patient would be well advised to be supplemented with which of the following?

a) Vitamin A

b) Vitamin B12

c) Vitamin C

d) Vitamin K

e) Linolenic acid.

17)- An 18-year-old male with sickle cell anemia develops severe right upper abdominal pain radiating to his lower right chest and his right flank 36 hours prior to admission to the ER. He also reports that his urine is the color of iced tea and his stool now has a light clay color. On examination, his temperature is slightly elevated, and heart rate is rapid. He is exquisitely tender to pressure over his right upper abdomen. The sclerae of his eyes are slightly yellowish in color.

What is the most likely cause of this patient’s symptoms?

a) A cholesterol-rich gallstone

b) A defect in the synthesis of bile acids

c) A defect in heme synthesis

d) A gallstone rich in calcium bilirubinate

e) A sickle cell crisis brought on by overexertion

18) Which of the following compounds directly inhibits the expression of the HMG-CoA reductase gene?

a) Squalene

b) HMG-CoA

c) Lanosterol

d) Isopentenyl pyrophosphate

e) Cholesterol

19) Which of the following vitamins can be used in high doses to treat hypercholesterolemia?

a) Niacin

b) Riboflavin

c) Pyridoxine

d) Folic acid

e) Thiamine.

20) A teenage boy presents with moderate to severe epigastric pain. Physical examination reveals extensive eruptive xanthomas and hepatosplenomegaly. A blood sample reveals milky plasma. Which of the following is the most likely lipoprotein to be elevated in this patient ‘s plasma?

a) Chylomicrons

b) Chylomicron remnants

c) HDL

d) IDL

e) LDL

21) A 25-year-old female was referred to a lipid research center for the investigation of moderate hypertriglyceridemia because the plasma lipid and lipoprotein profiles showed abnormalities. Both HDL and LDL were more buoyant and showed elevations in TG content with the mass of TG approximately the same as that of cholesterol. A deficiency in which of the following is the most likely cause of this patient’ s lipid abnormality?

a) Lecithin-cholesterol acyltransferase (LCAT)

b) Lipoprotein lipase

c) Apoprotein C-II

d) Hepatic lipase

e) Apoprotein B-100

22) Laboratory results for a patient with uncontrolled Type I diabetes mellitus reveal hyperglycemia (634 mg/dL) and hypertriglyceridemia (498 mg/dL). The most likely cause of hypertriglyceridemia in this patient is which of the following?

a) Deficiency in apoprotein C-II

b) Increased hepatic triglyceride synthesis

c) Decreased lipoprotein lipase activity

d) Deficiency in LDL receptors

e) Absence of hormone-sensitive lipase

 

Key to answers

1)-e,     

2)-a,      

3)-e,      

4)-c,      

5)-d,      

6)-b,              

7)-b,      

8)-b,      

9)-a,      

10)-e,   

11)-c,              

12)-b,

13)-d,   

14)-c,    

15)-d,   

16)-d,   

17)-d,   

18)-e,              

19)- a,  

20)-a,   

21)-d,   

22)-c