Catabolism of carbon skeleton of amino acids
Q. 1 Which of the following is not synthesised from tyrosine?
A | Norepinephrine | |
B |
Melatonin |
|
C |
Thyroxine |
|
D |
Dopamine |
Q. 1
Which of the following is not synthesised from tyrosine?
A |
Norepinephrine |
|
B |
Melatonin |
|
C |
Thyroxine |
|
D |
Dopamine |
Ans.
B
C
C
Explanation:
Q. 2
Which of the following is derived from tyrosine ‑
A |
Melatonin |
|
B |
Serotonin |
|
C |
Melanin |
|
D |
Niacin |
Ans.
Explanation:
Ans. is ‘c’ i.e., Melanin
Tyrosine is a precursor of many important compounds such as catecholamines (epinephrine, norepinephrine ), dopamine), thyroxine, triiodothryonine, melanin.
Q. 3
Enzyme deficient in tyrosinemia type 1
A |
Phenylalanine hydroxylase |
|
B |
Tyrosinase |
|
C |
Fumarylacetoacetate hydroxylase |
|
D |
Tyrosine transaminase |
Ans.
Explanation:
Ans:C
Tyrosinemia
It is a defect in the metabolism of tyrosine. It may be of the following types:-
- Tyrosinemia type-I (tyrosinosis/hepatorenal syndrome):- It is due to a defect in fumarylacetoacetate hydroxylase deficiency. Patients with chronic tyrosinosis are prone to develop cirrhosis and hepatic carcinoma. There is a cabbage-like odour in acute tyrosinosis.
- Tyrosinemia type – II (Richer-Hanhart syndrome):- It is due to deficiency of tyrosine transaminase (tyrosine aminotransferase).
- Neonatal tyrosinemia: – It is due to a deficiency of hydroxyphenyl pyruvate hydroxylase.