catabolism of protein and amino acid nitrogen

Question 1

Biosynthesis of urea

Answer 1

1. transamination
2. oxidative deamintaion of glutamate
3. ammonia transport
4. reactions of urea cycle

Question 2

Retards ubiquitination
A. Asp,arg
B. Met, ser
C.Iso, Leu
D.Val,Pro

Answer 2

B

Asp, Arg-accelerates

Question 3

Only amino acid that undergoes oxidative deamination at an appreciable rate in mammalian tissues
A.alanine
B.glutamic acid
C.glutamine
D.glutamate

Answer 3

D

Formation of ammonia from a-amino groups occurs mainly by L-glutamate

Question 4

Serves as carrier of amino groups during transamination

Answer 4

Pyridoxical phosphatey

Question 5

Formed during transfer of amino nitrogen to a-ketoglutarate

Answer 5

L-glutamate

Question 6

Conversion of a-amino nitrogen to ammonia by glutamate amintransferase and GDH
A. Transdeamination
B. Urea cycle
C. Alanine formation
D. Oxidative deamination

Answer 6

A.

Question 7

What function in the brain is impaired due to depletion of a-ketoglutarate?

Answer 7

TCA in neurons.

(Ammonia reacts with a-ketoglutarate to form glutamate

Question 8

Plays a major role in ammonia detoxification and acid-base homeostasis
A.glutamine synthase
B.glutamate synthase

Answer 8

A.

Glutamine increases in metabolic acidosis and decreases in metabolic alkalosis

Question 9

Major end product of nitrogen catabolism in humans

Answer 9

Urea

Question 10

Which of the following does not play a major metabolic role in urea synthesis of mammals
A.ornithine
B.citruline
C.glutamine
D.arginosuccinate

Answer 10

C.

No net lossor gain of a,b,d and arginine

Question 11

Functions solely as an enzy,e activator in synthesis of urea

Answer 11

N-acetylglutamate

Question 12

Rate-limiting enzyme of urea cycle

Answer 12

Carbamoyl phosphate synthase I

Question 13

Carbamoyl phosphate plus ornithine forms
A. Fumarate
B. Aspartate
C. Citrulline
D. arginine

Answer 13

C.

Formation of ornithine and metabolism of citrulline occurs in cytosol

Question 14

Citrulline plus Aspartate forms
A. Fumarate
B. Ornithine
C. Arginine
D. Arginosuccinate

Answer 14

D. Provides second nitrogen of urea

Question 15

Cleavage of arginosuccinate forms

Answer 15

Arginine and fumarate

Catalyzed by arginosuccinate lyase

Question 16

Trnasamination of oxaloacetate by glutamate aminotransferase reforms
A. Aspartate
B. Fumarate
C. Citrulline
D. Arginine

Answer 16

A.

Question 17

Releases urea by hydrolytic cleavage of guanidino group of arginine

Answer 17

Liver arginase

Ornithine and lysine are potent inhibitors

Question 18

Precursor of muscle relaxant nitric oxideA. Aspartate
B. Fumarate
C. Citrulline
D. Arginine

Answer 18

D

Question 19

Defect in carbamoyl phosphate syntthase I causes

Answer 19

Hyperammonemia type I

Question 20

Defect in ornithine transcarbamyolase

Answer 20

Hyperammonemia type 2

Question 21

Syndrome caused by mutation of ORNT 1 gene

Answer 21

HHH syndrome

Hyperornithemia, hyperammonemia, homocitrulinuria

Question 22

Technique of choice for screening neonates for inherited metabplic diseases

Answer 22

Tandem mass spectrometry