Q: Which of the following equations is used to estimate LDL cholesterol in plasma after a 12- to 14-hour fast?

$$\text{LDL cholesterol} = \text{total cholesterol} - (\frac{\text{TG}}{5} + \text{HDL cholesterol})$$

Question 1

Which of the following best describes the structural organization of a typical plasma lipoprotein particle?

Accepted Answer

A hydrophobic core of triacylglycerols and cholesteryl esters surrounded by a monolayer of phospholipids, free cholesterol, and apolipoproteins.

Question 2

Which apolipoprotein is essential for the activation of lipoprotein lipase (LPL) during the metabolism of chylomicrons and VLDL?

Accepted Answer

Apo C-II

Question 3

A patient presents with elevated plasma LDL cholesterol and premature coronary heart disease. Genetic analysis reveals a mutation causing loss of function in the LDL receptor. Which of the following best explains the biochemical consequence?

Accepted Answer

Decreased hepatic uptake of LDL, leading to increased plasma LDL and cholesterol.

Question 4

Which enzyme catalyzes the esterification of free cholesterol within cells, preparing it for storage?

Accepted Answer

ACAT (Acyl-CoA:cholesterol acyltransferase)

Question 5

Which of the following equations is used to estimate LDL cholesterol in plasma after a 12- to 14-hour fast?

Accepted Answer

$$	ext{LDL cholesterol} = 	ext{total cholesterol} - (\frac{	ext{TG}}{5} + 	ext{HDL cholesterol})$$

Question 6

Which lipoprotein is primarily responsible for the transport of dietary triacylglycerols from the intestine to peripheral tissues?

Accepted Answer

Chylomicrons

Question 7

A patient with type IIa hyperlipoproteinemia would be expected to have an excess of which lipoprotein in plasma?

Accepted Answer

LDL

Question 8

Which of the following drugs lowers plasma cholesterol by inhibiting the regulatory step in cholesterol biosynthesis and upregulating LDL receptor activity?

Accepted Answer

Statins

Question 9

Which of the following mechanisms is NOT a proposed antiatherogenic effect of HDL cholesterol?

Accepted Answer

Promotion of LDL oxidation to oxLDL

Question 10

A patient is prescribed gemfibrozil for hyperlipidemia. What is the primary mechanism by which this drug lowers plasma triglyceride levels?

Accepted Answer

Activation of lipoprotein lipase, promoting rapid turnover of VLDL

Question 11

Which of the following statements best explains why patients with nephrotic syndrome often have altered plasma lipoprotein levels?

Accepted Answer

Loss of proteins in urine stimulates hepatic lipoprotein synthesis, increasing plasma lipoproteins.

Question 12

Which of the following is a direct effect of increased intracellular cholesterol in hepatocytes following LDL uptake?

Accepted Answer

Inhibition of HMG-CoA reductase activity

Question 13

Which of the following best describes the fate of chylomicron remnants after their triacylglycerol content is depleted?

Accepted Answer

They are taken up by the liver via apo E receptor-mediated endocytosis and degraded by lysosomal enzymes.

Question 14

Which of the following is a distinguishing feature of HDL compared to other plasma lipoproteins?

Accepted Answer

Nascent HDL is discoidal and becomes spherical after LCAT action.

Question 15

A patient with a mutation in the gene encoding apo B-100 would most likely have impaired metabolism of which lipoprotein?

Accepted Answer

LDL

Question 16

Which of the following best explains why statin therapy reduces both fatal and nonfatal heart attacks in patients with coronary artery disease?

Accepted Answer

Statins lower plasma LDL cholesterol, reducing atherosclerotic plaque formation.

Question 17

Which of the following is a secondary cause that can alter plasma lipoprotein levels?

Accepted Answer

Diabetes mellitus

Question 18

Which of the following statements about the endogenous pathway of lipid transport is correct?

Accepted Answer

VLDL is synthesized in the liver, delivers triglycerides to tissues, and is converted to LDL via IDL.

Question 19

Which of the following is a direct effect of hepatic lipase activity?

Accepted Answer

Hydrolysis of phospholipids and triglycerides in HDL and IDL

Plasma Lipoproteins: Structure, Metabolism, and Clinical Implications

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