Midterm II: Past Paper Questions

Question 1

Which lipoprotein carries cholesterol to the extrahepatic tissues?

• chylomicron?
• HDL?
• IDL?
• LDL?
• VLDL?

Answer 1

LDL

Question 2

Free fatty acids in the bloodstream are:

• bound to hemoglobin?
• carried by the protein serum albumin?
• freely soluble in the aqueous phase of blood?
• nonexistent; the blood does not contain FFA?
• present at levels that are independent of epinephrine?

Answer 2

carried by protein serum albumin

Question 3

Lipoprotein lipase acts in:

• hydrolysis of TAGs of plasma lipoproteins to supply fatty acids to various tissues?
• intestinal uptake of dietary fat?
• intracellular lipid breakdown of lipoproteins?
• lipoprotein breakdown to supply needed amino acids?
• none of the above?

Answer 3

hydrolysis of TAGs of plasma lipoproteins to supply fatty acids to various tissues

Question 4

The role of hormone-sensitive TAG lipase is to:

• Hydrolyze lipids stored in the liver?
• hydrolyze TAGs stored in adipose tissue?
• hydrolyze membrane phospholipids in hormone-producing cells?
• synthesize TAGs in the liver
• synthesize lipids in adipose tissue

Answer 4

hydrolyze TAGs stored in adipose tissue

(mobilizes stored fats, inhibited by insulin)

Question 5

Which of the statements about TAG synthesis is correct?

• phosphatidate is not on the pathway of TAG synthesis
• mammals are unable to convert carbohydrates into TAG
• insulin stimulates conversion of dietary carbs into TAG
• humans can store more energy in glycogen than TAG

Answer 5

Insulin stimulates conversion of dietary carbohydrates into triacylglycerols

Question 6

The function of the NPC1L1 transporter is: (one answer)

• to pump out bile salts into biliary capillaries
• to pump out bile salts into the epithelial intestinal cells
• to pump in cholesterol into the epithelial intestinal cells
• to pump out cholesterol into the biliary capillaries
• to pump out either cholesterol or bile salts into the biliary capillaries

Answer 6

to pump in cholesterol into the epithelial intestinal cells

Question 7

Which of the listed states is characterized by elevated concentration of free fatty acids in the blood plasma? (more than 1 answer)

• following release of glucagon
• prolonged fasting
• after a meal
• in the course of insulin therapy

Answer 7

• following release of glucagon (see mobilization of TAG stored in adipose tissue slide)
• Prolonged Fasting

Question 8

Which of the following statements are true for leptin? (more than one answer)

• Leptins are secreted by adipocytes
• Mice lacking leptin receptors are obese
• High leptin level usually means large volume of adipose tissue
• Leptins increase appetite
• Leptins directly regulate insulin secretion

Answer 8

• Leptins are secreted by adipocytes
• Mice lacking leptin receptors are obese
• High leptin level usually means large volume of adipose tissue

Question 9

Which of the following statements is not valid for lipoprotein lipase?

• An enzyme with a low Km is present in the mammary gland
• VLDL carries its cofactor
• it degrades the majority of plasma triacylglycerols
• its activity in adipose tissue increases in the fasting state
• it is bound to the luminal surface of capillary endothelial cells

Answer 9

Its activity in adipose tissue increases in the fasting state

(adipose tissue has higher Km than heart tissue, allowing redirection of TAG’s from adipose tissue to the heart in fasting state. see Harper p. 257)

Question 10

Select the statements relevant to control mechanisms involved in the regulation of the plasma cholesterol level: (more than one answer)

1. LDL receptors are under transcriptional control based on SREBP
2. SREBP is released following cholesterol-dependent proteolysis of a precursor protein
3. SREBP is a nuclear receptor that binds sterols
4. LXR is a nuclear receptor that binds sterols
5. Cyp7a is under transcriptional control based on LXR
6. LXR prevents the release of cholesterol from the cells

Answer 10

1, 2, 4, 5

• LDL receptors are under transcriptional control based on SREBP
• SREBP is released following cholesterol-dependent proteolysis of a precursor protein
• LXR is a nuclear receptor that binds sterols
• Cyp7a is under transcriptional control based on LXR

Question 11

Lipoprotein Lipase hydrolyzes TAGs of the following lipoproteins: (more than one answer)

• VLDL
• nascent chylomicron
• mature chylomicron
• chylomicron remnant
• HDL3

Answer 11

• VLDL
• mature chylomicron
• HDL3 (this one seems weird, but according to answer sheet is correct)

Question 12

Which factors in which sequence of the list reflects most completely the major route of cholesterol stored in extrahepatic tissue to its disposal in the intestine as bile salts?

1. LDL
2. HDL
3. Cholesterolester transfer protein (CETP)
4. lipoprotein lipase
5. hepatic lipase
6. LDL receptor
7. Cyp7a
8. ABCA1 transporter

Answer 12

8, 2, 3, 1, 6, 7

• ABCA1 transporter
• HDL
• CETP
• LDL
• LDL receptor
• Cyp7a

Question 13

Which statements are valid for the scavenger receptors (SR)?

1. SR’s are alternative specific receptors for the uptake of LDL
2. Following binding of LDL to SRA, the ligand-receptor complex is internalized
3. SRB1 is the major receptor for the uptake of oxidized LDL in macrophages
4. SRA is under cholesterol-dependent transcriptional control
5. SRB1 participates in the uptake of HDL-cholesterol in the liver

Answer 13

2, 5

• Following binding of LDL to SRA, the ligand-receptor complex is internalized
• SRB1 participates in the uptake of HDL-cholesterol in the liver

Question 14

Plasma level of unesterified fatty acids is increased: (multiple answers)

• in starvation
• in well-fed state
• by glucagon
• by ACTH
• by insulin

Answer 14

• in starvation
• by glucagon
• by ACTH