Deck 28: Lipids: Lipoproteins

Question 1

An increase in which of the following apolipoproteins would most likely be associated with a reduced risk for the development of atherosclerosis?

A) apo(a)
B) apoA-I
C) apoC-I
D) apoC-II
E) apoE

Answer 1

apoE

Question 2

The hypercholesterolemia that is associated with familial hypercholesterolemia is due to which of the following?

A) abnormally elevated production of LDL
B) abnormally elevated production of VLDL by the liver
C) abnormally reduced production of HDL, resulting in a diminished capacity of reverse cholesterol transport
D) defective LDL receptors leading to reduced uptake of plasma LDL and IDL
E) defective remnant receptors on hepatic cells, leading to reduced uptake of chylomicron remnants

Answer 2

defective LDL receptors leading to reduced uptake of plasma LDL and IDL

Question 3

A 13-year-old girl presents with extensive eruptive xanthomas and hepatosplenomegaly. She does not have type 1 or type 2 diabetes as an analysis of circulating insulin and glucose levels indicates they are normal. Examination of plasma indicates that it quite milky, indicating a lipemia. Analysis of the lipid content of the plasma shows a massive accumulation of chylomicrons and triglycerides. The teenager is placed on a fat-free diet, which reduces the lipemia and all of the other clinical manifestations. A deficiency in which of the following apolipoproteins would account for the observed symptoms of this particular hyperlipoproteinemia?

A) apoA-I
B) apoA-IV
C) apoB-100
D) apoC-II
E) apoE

Answer 3

apoC-II

Question 4

A deficiency in which of the following proteins would have the most significant effect on the ability of HDL to deliver nonhepatic cholesterol to LDL?

A) apoB-48
B) apoB-100
C) apoE
D) cholesteryl ester transfer protein (CETP)
E) lecithin:cholesterol acyltransferase (LCAT) ratio

Question 5

Overexpression of Lp-PLA2 is associated with an increased risk of cardiovascular disease. Which of the following represents a primary mechanism for this effect of the enzyme?

A) binding to the LDL receptor on hepatocytes
B) disulfide bonding to apoB-100 in LDL
C) hydrolysis of oxidized phospholipids
D) inactivation of platelet-activating factor
E) interaction with tissue plasminogen activator

Question 6

A 2-month-old male child is presented with microcephaly (head size smaller than normal), micrognathia (abnormally small lower jaw), ptosis (drooping eyelids), a small upturned nose, cleft palate, and ambiguous genitalia. Following biochemical analysis it is determined that the infant has highly elevated levels of 7-dehydrocholesterol in his tissues. These findings are indicative of which of the following disorders?

A) Dubin-Johnson syndrome
B) familial intrahepatic cholestasis type 2
C) Rotor syndrome
D) Smith-Lemli-Opitz syndrome
E) Tangier disease

Question 7

Lipoprotein lipase (LPL) is the endothelial cell- associated enzyme necessary for release of fatty acids from circulating lipoproteins. Which of the following apolipoproteins is required to activate LPL-mediated release of fatty acids from chylomicrons?

A) apoA
B) apoB-48
C) apoB-100
D) apoC-II
E) apoE

Question 8

A 28-year-old man has the following symptoms: diffuse grayish corneal opacities, anemia, proteinuria, and hyperlipemia. His renal function is compromised and serum albumin level is elevated. Plasma triglycerides and unesterified cholesterol levels are elevated, as are levels of phosphatidylcholine. These symptoms are indicative of which of the following lipoprotein-associated disorder?

A) Bassen-Kornzweig syndrome
B) familial hypercholesterolemia (FH)
C) familial hypertriacylglycerolemia
D) familial lecithin-cholesterol acyltransferase (LCAT) deficiency
E) Wolman disease

Question 9

Which of the following apoproteins is found exclusively associated with chylomicrons?

A) apoA
B) apoB-48
C) apoC-II
D) apoD
E) apoE

Question 10

High plasma levels of the lipoprotein particle identified as lipoprotein(a) (Lp[a]) have been shown to be a primary risk factor for coronary heart disease and stroke. Lp(a) is a unique lipoprotein assembled from low-density lipoprotein (LDL) and a single glycoprotein called apolipoprotein(a) (apo[a]). Apo(a) is associated with LDL via a disulfide linkage to which other apolipoprotein?

A) apoA-I
B) apoB-48
C) apoB-100
D) apoC-II
E) apoE

Question 11

A 16-year-old teenager 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 the plasma of this patient accounting for the milky appearance?

A) apo(a)
B) chylomicrons
C) HDL
D) IDL
E) LDL

Question 12

Laboratory results for a patient with uncontrolled type 1 diabetes reveal hyperglycemia (634 mg/dL) and hypertriglyceridemia (498 mg/dL). Which of the following represents the most likely cause of the hypertriglyceridemia in this patient?

A) absence of hormone-sensitive lipase
B) decreased lipoprotein lipase activity
C) deficiency in apoprotein C-II
D) deficiency in LDL receptors
E) increased hepatic triglyceride synthesis

Question 13

A 23-year-old female presents with low red blood cell count, corneal opacities, and renal insufficiency. She is diagnosed with a deficiency in ratio of lecithin to cholesterol acyltransferase (LCAT). In which of the following reactions is LCAT involved?

A) converting cholesterol to cholesterol esters
B) hydrolysis of HDL
C) promoting uptake of HDL into liver cells
D) transfer of cholesterol esters from HDL to VLDL
E) uptake of cholesterol from liver cells

Question 14

You have referred a 27-year-old woman to a lipid research center for investigation of moderate hypertriglyceridemia. Analysis of her serum revealed the presence of abnormal lipid and lipoprotein profiles. Both HDL and LDL were less dense than normal and showed significant elevations in triglyceride content with the mass of triglycerides approximately the same as that of cholesterol. A deficiency in which of the following is the most likely cause of the observed lipid abnormalities?

A) apoB-100
B) cholesterol ester transfer protein (CETP)
C) hepatic triglyceride lipase
D) lecithin-cholesterol acyltransferase (LCAT)
E) lipoprotein lipase

Question 15

You are carrying out a clinical trial of a new investigational drug for the treatment of hypercholesterolemia. Results of your studies indicate that consumption of the drug results in clear elevation in the level of circulating HDL in most of the test subjects. Given these results, which of the following proteins is most likely the target of the investigational drug?

A) apoB-100
B) apoC-II
C) cholesterol ester transfer protein (CETP)
D) hepatic triglyceride lipase (HTGL)
E) lecithin-cholesterol acyltransferase (LCAT)

Question 16

Obesity is an epidemic in the United States and other industrialized countries, resulting in significant health consequences and expense. Therefore, discovering novel therapies for modifying food intake would have particular benefits to the treatment of obesity. Recent work has demonstrated that feeding behaviors are reduced following the consumption of fat through the actions of which of the following apolipoproteins?

A) apoA-IV
B) apoB-100
C) apoB-48
D) apoC-II
E) apoE

Question 17

You are studying the activities of a compound that is purported to be an inhibitor of the antioxidant functions of HDL. Administration of this compound to experimental animals does indeed result in elevated levels of oxidized LDL (oxLDL) in the plasma. Which of the following proteins is the most likely target of this compound accounting for the reduced antioxidant function of HDL?

A) apoA-I
B) apoC-II
C) apoE
D) cholesterol ester transfer protein (CETP)
E) lecithin-cholesterol acyltransferase (LCAT)

Question 18

Which of the following statements best distinguishes VLDL from chylomicrons?

A) only chylomicrons are involved in the delivery of triglyceride to the adipocyte
B) only chylomicrons are produced by the liver
C) only chylomicrons contain phospholipids and cholesteryl esters
D) only VLDL are produced during periods of starvation
E) VLDL have a higher percentage of triglyceride than chylomicrons

Question 19

Plasma triglyceride derived from dietary fats is transported in the plasma as which of the following?

A) albumin complexes
B) chylomicrons
C) HDL
D) LDL
E) VLDL

Question 20

An increased plasma concentration of cholesterol is most likely to be caused by a deficiency of which of the following?

A) bile acid synthetic enzymes
B) HDL receptors
C) 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase
D) insulin receptors
E) LDL receptors

Question 21

A 23-year-old man is found to be incapable of producing chylomicrons. Which of the following is the most likely consequence of this disorder?

A) fasting hyperglycemia
B) impaired absorption of dietary lipids
C) increased risk of hypertriglyceridemia
D) increased risk of lactic acidosis
E) increased serum urea nitrogen concentration

Question 22

A 30-year-old woman is brought to the physician because of a rash on her arms for 2 months and severe abdominal pain for the past 24 hours. She indicates that she has had intermittent upper abdominal pain during the past 1 to 2 years. Physical examination shows yellow papules on the extensor surfaces of the upper extremities. Palpation of the epigastric region of her abdomen causes pain. Her blood work shows serum amylase activity is increased and fasting serum concentrations of chylomicrons and triglycerides are markedly increased. Which of the following changes in apolipoprotein concentrations is most likely in this patient?

A) decreased apoA-I
B) decreased apoB-III
C) decreased apoC-II
D) increased apoB-100
E) increased apoE

Question 23

A genetically based deficiency of which of the following will most likely result in decreased lipoprotein lipase activity?

A) apoC-II
B) bile salt deconjugase
C) ceruloplasmin
D) hormone-sensitive lipase
E) pancreatic lipase

Question 24

The primary function of LDL is to transport which of the following?

A) cholesterol to peripheral tissues
B) cholesterol from tissues to the liver
C) dietary-derived lipid to the liver
D) free fatty acids from adipocytes
E) triglycerides to adipocytes

Question 25

A 40-year-old man with a 10-year history of type 1 diabetes mellitus comes to the physician for a routine examination. He was diagnosed with pancreatitis 25 years ago after a 2-year history of recurrent abdominal pain. Physical examination shows a thin habitus and abdominal tenderness. After a 12-hour fast, his serum triglyceride concentration is 4000 mg/dL (normal = 60-134). Intravenous heparin is administered in order to examine the patient's lipoprotein lipase activity. Plasma lipoprotein lipase activity is assayed and is extremely deficient in this man's blood. Which of the following proteins is most likely deficient in this patient?

A) apoA-I
B) apoB-48
C) apoB-100
D) apoC-II
E) apoE

Question 26

A 20-year-old man comes to the physician because of recurrent episodes of acute abdominal pain since childhood. The pain usually occurs after eating a meal with a rich dessert. Physical examination shows a small number of xanthomas on the buttocks and knees. A fasting lipid analysis shows milky plasma; there is markedly increased serum concentration of triglycerides and chylomicrons. His serum LDL-cholesterol concentration is within the reference range, and serum HDL-cholesterol concentration is decreased. This patient most likely has a defect of which of the following proteins?

A) apoA-I
B) apoC-II
C) apoE
D) HDL receptor
E) LDL receptor

Question 27

Cholesterol is transported in the bloodstream in LDL, which bind to specific membrane receptors on the peripheral tissue cell membranes. The cholesterol then enters these cells by which of the following mechanisms?

A) carrier-mediated diffusion on the cholesterolspecific carrier in the cell membrane
B) cholesterol-specific gated channel
C) endocytosis, where it is released from the LDL in the lysosomes
D) by first being converted to cholesterol esters by plasma enzyme lecithin-cholesterol acyltransferase (LCAT)

Question 28

Which of the following is involved in the transport of newly synthesized triglycerides from the liver to adipose tissue?

A) chylomicrons
B) HDL
C) IDL
D) LDL
E) VLDL

Question 29

A defect in which of the following proteins or complexes would result in the inability of HDL to transfer peripheral tissue cholesterol to circulating LDL?

A) acyl-CoA:cholesterol acyltransferase (ACAT) ratio
B) clathrin
C) lecithin-cholesterol acyltransferase (LCAT)
D) lipoprotein lipase
E) phosphorylated mannose residue

Question 30

Which of the following is most likely to occur to the LDL receptor after it has been dissociated from LDL in the acidic early endosome?

A) digested by proteasomes in the cytosol after release from the endosome
B) recycled back to the cell membrane from the endosome in transport vesicle
C) recycled into a vesicle in the trans-Golgi complex and transported to the cell membrane
D) transcytosis
E) transferred to lysosomes where it is degraded by lysosomal enzymes