Metabolism of Chylomicron

Metabolism of Chylomicron

Q. 1 In chylomicrons, the Principle Apo-protein is:
 A Apo A-I
 B Apo A-II
 C Apo B-100
 D Apo B-48
Q. 1 In chylomicrons, the Principle Apo-protein is:
 A Apo A-I
 B Apo A-II
 C Apo B-100
 D Apo B-48
Ans. D

Explanation:

Apo B-48


Q. 2

Which of the following are incorporated into the core of nascent chylomicrons?

 A

Triglyceride

 B

Triglyceride and Cholesterol

 C

Triglyceride, Cholesterol and Phospholipids

 D

Free fatty acids

Q. 2

Which of the following are incorporated into the core of nascent chylomicrons?

 A

Triglyceride

 B

Triglyceride and Cholesterol

 C

Triglyceride, Cholesterol and Phospholipids

 D

Free fatty acids

Ans. B

Explanation:

After ingestion of a meal, dietary fat (triglyceride) and cholesterol are absorbed into the cells of the small intestine and are incorporated into the core of nascent chylomicrons.


Q. 3

The chyle from intestine is rich with chylomicrons. Which of the following form the protein core of chylomicrons?

 A

Triglyceride only

 B

Triglyceride + cholesterol

 C

Triglyceride + cholesterol + phospholipid

 D

Only cholesterol

Q. 3

The chyle from intestine is rich with chylomicrons. Which of the following form the protein core of chylomicrons?

 A

Triglyceride only

 B

Triglyceride + cholesterol

 C

Triglyceride + cholesterol + phospholipid

 D

Only cholesterol

Ans. C

Explanation:

The triacylglycerol, cholesterol ester and phospholipid molecules along with apoproteins B48, and apo-A are incorporated into chylomicrons.
 

Four major groups of lipoproteins:

  • Chylomicrons, derived from intestinal absorption of triacylglycerol and other lipids.
  • Very low density lipoproteins (VLDL, or pre–lipoproteins), derived from the liver for the export of triacylglycerol.
  • Low-density lipoproteins (LDL, or -lipoproteins), representing a final stage in the catabolism of VLDL.
  • High-density lipoproteins (HDL, or -lipoproteins), involved in cholesterol transport and also in VLDL and chylomicron metabolism.

Triacylglycerol is the predominant lipid in chylomicrons and VLDL, whereas cholesterol and phospholipid are the predominant lipids in LDL and HDL, respectively.

Ref: Botham K.M., Mayes P.A. (2011). Chapter 25. Lipid Transport & Storage. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper’s Illustrated Biochemistry, 29e.

Quiz In Between


Q. 4

A human subject takes part in a nutritional research study. After ingesting a very fatty meal, serum samples are taken for research studies at 1 hour and 3 hours. These studies measure the average diameter of the chylomicrons, showing an average chylomicron diameter of 500 nm at 1 hour, which drops to an average diameter of 150 nm at 3 hours. Where is the enzyme responsible for this change located?

 A

Adipocytes

 B

Endothelial cells

 C

Enterocytes

 D

Hepatocytes

Q. 4

A human subject takes part in a nutritional research study. After ingesting a very fatty meal, serum samples are taken for research studies at 1 hour and 3 hours. These studies measure the average diameter of the chylomicrons, showing an average chylomicron diameter of 500 nm at 1 hour, which drops to an average diameter of 150 nm at 3 hours. Where is the enzyme responsible for this change located?

 A

Adipocytes

 B

Endothelial cells

 C

Enterocytes

 D

Hepatocytes

Ans. B

Explanation:

Chylomicrons are produced by enterocytes (intestinal epithelial cells), using gut luminal triglycerides for the source of the lipid. The chylomicrons are secreted into the gut lymphatic system, and from there drain eventually into the systemic venous system from the thoracic duct, and hence into the serum portion of the blood. They are initially large and have a very high triglyceride content. With time, lipoprotein lipase releases triglycerides from the chylomicron core by hydrolyzing them to more easily absorbed fatty acids. The enzyme is located on the external surface of the vascular endothelium of tissues with triglyceride needs such as skeletal muscle, cardiac muscle tissue, and lactating breast. The result of lipoprotein lipase activity is that the chylomicrons shrink in size.

While adipose tissue can utilize chylomicrons, lipoprotein lipase is located on the endothelial cells rather than adipocytes. Adipocytes have an adipose tissue lipase, which is an intracellular enzyme that can cleave triglycerides to glycerol and fatty acids, allowing them to be released into the circulation when chylomicrons are low.
 
Enterocytes have the ability to pick up mixed micelles from the gut lumen for repackaging in the smooth endoplasmic reticulum as chylomicrons.
Hepatocytes pick up the chylomicron remnants after the lipoprotein lipase shrinks them.
Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 26. Digestion, Absorption, & Nutritional Principles. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.

Q. 5

Which helps in the transport of chylomicrons from intestine to liver :

 A

Apoprotein B

 B

Apoprotein A

 C

Apoprotein C

 D

Apoprotein E

Q. 5

Which helps in the transport of chylomicrons from intestine to liver :

 A

Apoprotein B

 B

Apoprotein A

 C

Apoprotein C

 D

Apoprotein E

Ans. A

Explanation:

A i.e. Apoprotein B


Q. 6

Major apolipoprotein of chylomicrons

 A

B-100

 B

D

 C

B-48

 D

None

Q. 6

Major apolipoprotein of chylomicrons

 A

B-100

 B

D

 C

B-48

 D

None

Ans. C

Explanation:

Ans. is ‘c’ i.e., B-48 

Quiz In Between



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