Carnitine

Carnitine

Q. 1

Amino acid used in Carnitine synthesis is which of the following?

 A

Alanine

 B

Lysine

 C

Arginine

 D

Tyrosine

Q. 1

Amino acid used in Carnitine synthesis is which of the following?

 A

Alanine

 B

Lysine

 C

Arginine

 D

Tyrosine

Ans. B

Explanation:

Carnitine is a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine. In living cells, it is required for the transport of fatty acids from the cytosol into the mitochondria during the breakdown of lipids for the generation of metabolic energy. It is widely available as a nutritional supplement.


Q. 2

Carnitine-acylcarnitine translocase acts as an inner membrane exchange transporter. Carnitine is synthesized from:

 A

Alanine

 B

Arginine

 C

Lysine

 D

Glycine

Q. 2

Carnitine-acylcarnitine translocase acts as an inner membrane exchange transporter. Carnitine is synthesized from:

 A

Alanine

 B

Arginine

 C

Lysine

 D

Glycine

Ans. C

Explanation:

Levocarnitine (L-carnitine):

  • It is an endogenous carboxylic acid that facilitates transport of long-chain fatty acids into mitochondria for beta-oxidation and prevents intracellular accumulation of toxic acyl-CoA. 
  • L-Carnitine is ubiquitous in diets rich in meats and dairy products and is also synthesized in the body from the amino acids lysine and methionine.
  • Valproic acid causes carnitine deficiency, resulting in mitochondrial dysfunction. 
  • Primary defects of carnitine transport may manifest as Reyes syndrome, cardiomyopathy, or skeletal myopathy with hypotonia.
 
Ref: Thomas J.A., Van Hove J.L. (2012). Chapter 36. Inborn Errors of Metabolism. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.

Q. 3

The substance essential for transfer of fatty acids across mitochondrial membrane:

 A

Cera tine

 B

Ceratinine

 C

Carnitine

 D

Coenyzme A

Q. 3

The substance essential for transfer of fatty acids across mitochondrial membrane:

 A

Cera tine

 B

Ceratinine

 C

Carnitine

 D

Coenyzme A

Ans. C

Explanation:

C i.e. Carnitine


Q. 4

All are true about 0-oxidation except:

 A

Activation of FA is a must

 B

Carnitine palmitoyl transferase I is present in outer mitochondrial membrane

 C

Carnitine palmitoyl trasferase II is present in mitochondrial matrix

 D

FA activation requires 2ATP.

Q. 4

All are true about 0-oxidation except:

 A

Activation of FA is a must

 B

Carnitine palmitoyl transferase I is present in outer mitochondrial membrane

 C

Carnitine palmitoyl trasferase II is present in mitochondrial matrix

 D

FA activation requires 2ATP.

Ans. C

Explanation:

C i.e. Carnitine palmitoyl trasf erase II is present in mitochondrial matrix

Long chain activated fatty acid penetrate the inner mitochondria( membrane only in combination with carnitineQ. Carnitine, a carrier molecule, acts like a ferry boat and transport long chain acyl- CoA across mitochondiral membrane otherwise inner mitochondrial membrane is impermeable to acyl -CoA.


Q. 5

Hepatotoxicity caused by valproate can be prevented by-

 A

Zinc

 B

Carnitine

 C

Pyridoxine

 D

Vit K

Q. 5

Hepatotoxicity caused by valproate can be prevented by-

 A

Zinc

 B

Carnitine

 C

Pyridoxine

 D

Vit K

Ans. B

Explanation:

Ans. is ‘b’ i.e., Carnitine

o Valprate is a hepatotoxic drug.

o Hepatotoxicity is due to its metabolite 4-pantenoic acid.

o Valprate hepatotoxicity is more common in persons with mitochondrial enzyme deficiency and may be ameliorated by administration of Carnitine, which valproate therapy can deplete.


Q. 6

Which is involved in transport of long chain acyl-CoA in mitochondria?    

 A

Ornithine

 B

Xanthine

 C

Carnitine

 D

Albumin

Q. 6

Which is involved in transport of long chain acyl-CoA in mitochondria?    

 A

Ornithine

 B

Xanthine

 C

Carnitine

 D

Albumin

Ans. C

Explanation:

 

In humans carnitine is synthesized from protein-derived trimethyllysine in liver, brain and kidney.

Muscles take up carnitine from the blood in an exchange-diffusion process with endogenous deoxycarnitine, the immediate precursor of carnitine.

Besides catalysing the transport of long-chain acyl groups in mitochondria, carnitine is necessary for the export of intramitochondrially produced short-chain acyl residues and for the trapping and the elimination of unphysiological compounds (benzoic, pivalic, valproic acids etc.).


Q. 7

Role of carnitine in lipid metabolism ‑

 A

Catalyzation of the cyclization sequence

 B

Essential for extracellular transfer of fatty acids

 C

Essential for biosynthesis of fatty acids

 D

Transfer of activated long chain FFA into mitochondria

Q. 7

Role of carnitine in lipid metabolism ‑

 A

Catalyzation of the cyclization sequence

 B

Essential for extracellular transfer of fatty acids

 C

Essential for biosynthesis of fatty acids

 D

Transfer of activated long chain FFA into mitochondria

Ans. D

Explanation:

Ans. is ‘d’ i.e., Transfer of activated long chain FFA into mitochondria

Activated long chain fatty acid (acyl CoA) cannot penetrate inner mitochondria! membrane.

Acyl group of acyl CoA is transferred to carnitine, resulting in formation of acylcarnitine.

Acylcarnitine is then transported across the inner mitochondria! membrane into the mitochondria! matrix by translocase.

Once inside the mitochondrion, acyl group of acylcarnitine is transferred back to CoA, resulting in formation of acyl-CoA which undergoes 13-oxidation.


Q. 8

Carnitine is synthesised from ‑

 A

Methionine

 B

Arginine

 C

Histidine

 D

Choline

Q. 8

Carnitine is synthesised from ‑

 A

Methionine

 B

Arginine

 C

Histidine

 D

Choline

Ans. A

Explanation:

 

Carnitine is synthesized from amino acids lysine and methionine.



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