Metabolism Of Membrane Lipids.
- 1.A 5-year-old girl is presented with hepatosplenomegaly, abnormal bleeding, defects in long bone development, and neurological dysfunction. A liver biopsy reveals an accumulation of glucocerebroside. These symptoms indicate the child is suffering from:
- A.
Fabry's disease
- B.
Niemann-Pick disease
- C.
Krabbe's disease
- D.
Gaucher's disease
- E.
Hurler syndrome
- 2.3-hydroxy, 3-methylglutaryl-CoA (HMG-CoA) is not only the substrate for the rate-limiting enzyme of cholesterol synthesis, but also an intermediate in the synthesis of:
- A.
Heme
- B.
Purines
- C.
Pyrimidines
- D.
Ketone bodies
- E.
Glutathione
- 3.The alleles in the ABO blood group system code for:
- A.
Integral membrane proteins
- B.
Glycosyl transferases
- C.
Peripheral membrane proteins
- D.
Cytoskeletal proteins
- E.
Phosphoglyceride-synthesizing enzymes
- 4.A pregnant woman mentions that 2 years ago, her first child died 2 weeks after birth because the newborn’s “lungs were immature” at birth. Since you are planning a C-section, you want to determine first whether there is a risk of respiratory problems for her current baby. Which of the following results from an analysis of her amniotic fluid would indicate a high risk?
- A.
A low ratio of free cholesterol/cholesterol esters
- B.
An elevated glucose level
- C.
A low lecithin/shingomyelin ratio
- D.
An elevated level of phosphatidylglycerol
- E.
A reduced level of platelet-activating factor
- 5.One in 30 Ashkenazi Jews carries a mutation for Tay-Sachs disease in the heterozygous state. The heterozygotes can be identified by measuring one of the following enzymes in cultured leucocytes:
- A.
Glucocerebrosidase
- B.
Hexosaminidase A
- C.
Iduronate sulfatase
- D.
Ceramidase
- E.
B-galactosidase
- 6.Excess cholesterol needs to be transported to the liver because it cannot be metabolized in most extrahepatic tissues. This 'reverse' transport of cholesterol requires a lipoprotein that is not required for other routes of cholesterol transport. This lipoprotein is:
- A.
IDL
- B.
LDL
- C.
HDL
- D.
VLDL
- E.
Lipoprotein(a)
- 7.Hypercholesterolemic patients taking HMG-CoA reductase inhibitors (statins) produce less cholesterol from endogenous synthesis. Lower intracellular cholesterol levels induce which of the following regulatory changes?
- A.
Enhanced VLDL formation in the liver
- B.
Down-regulation of HMG-CoA reductase
- C.
Higher lipoprotein lipase (LPL) activity
- D.
Higher plasma chylomicron concentration
- E.
An increased number of LDL receptors
- 8.Routine blood studies on an infant show turbid plasma with markedly elevated levels of triacylglycerol. A sample of plasma that has been left in the refrigerator overnight has cream-colored material floating on top. The underlying plasma is clear. Which type of hyperlipoproteinemia is most likely present in this infant?
- A.
Type I
- B.
Type III
- C.
Type IIb
- D.
Type IIa
- E.
Type IV
- 9.You culture fibroblasts from a patient in the laboratory. In order to up-regulate the low-density lipoprotein (LDL) receptors in these cells you should:
- A.
Add cholesterol esters to the medium
- B.
Add excess LDL to the medium
- C.
Inhibit HMG-CoA reductase
- D.
Inhibit the activity of acyl-CoA-cholesterol-acyl transferase (ACAT)
- E.
Add cholestyramine
- 10.A 5-year-old boy develops severe stomach pain after eating a big piece of fatty cheesecake. Serum amylase is found to be mildly elevated. The plasma triglyceride level is 1200 mg/dL, and the total cholesterol is 220 mg/dL. The parents mention that the child does not like fatty foods at all, but this was the first time he tasted cheesecake. Which apolipoprotein might be deficient in this patient to account for his fat intolerance?
- A.
A-I
- B.
C-II
- C.
B-100
- D.
C-III
- E.
E
- 11.A 33-year-old man is found to have tendon xanthomas. When questioned about his lifestyle he says that he exercises regularly, eats balanced meals and is not in any physical distress. A blood analysis reveals plasma total cholesterol of 350 mg/dL and triglycerides of 70 mg/dL. He is treated with cholestyramine and a statin and sent for further analysis. His hyperlipidemia is best classified as:
- A.
Type I
- B.
Type V
- C.
Type III
- D.
Type IV
- E.
Type IIa
- 12.Statins are the most important type of cholesterol-lowering drug, and they lower specifically LDL rather than HDL cholesterol. How do the statins lower LDL cholesterol?
- A.
By reducing the synthesis of apo B-100, the major structural protein of VLDL and LDL
- B.
By stimulating the conversion of excess cholesterol to bile acids in the liver, thereby depleting cholesterol for LDL synthesis
- C.
By stimulating the transfer of cholesterol esters from VLDL and LDL to HDL
- D.
By inhibiting HMG-CoA reductase, thereby preventing cholesterol synthesis and forcing the cells to obtain their cholesterol from LDL
- E.
By stimulating the efflux of free cholesterol from cell membranes to HDL, thereby reducing the amount of cholesterol that is partitioned into LDL
- 13.On physical examination you notice that a patient has tendon xanthomas. A blood analysis reveals a total cholesterol level of 350 mg/dL, which is due mainly to raised levels of LDL, and normal levels of triglyceride. What other investigation would be helpful in this patient?
- A.
Look for eruptive xanthomas
- B.
Do a VLDL analysis
- C.
Isolate the patient's lymphocytes and look for the number of LDL receptors
- D.
Check for hyperthyroidism
- E.
Do a fasting blood glucose
- 14.Cholestyramine can be used for the treatment of hypercholesterolemia, either alone or in combination with a statin. Which enzyme is most immediately affected by cholestyramine tratment?
- A.
Cholesterol ester transfer protein
- B.
Acyl-CoA-cholesterol acyltransferase (ACAT)
- C.
7a-hydroxylase
- D.
HMG-CoA reductase
- E.
Lecithin-cholesterol acyltransferase (LCAT)
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