31. Nitrogen Metabolism

Question 1

protein turnover is

Answer 1

300-400 g per day

Question 2

amount of protein degraded and resynthesized from amino acids

Answer 2

protein turnover

Question 3

sum of all free amino acids in cells and extracellular fluid

Answer 3

amino acid pool

Question 4

sources of amino acid pool

Answer 4

• degradation and turnover of body protein
• dietary intake
• synthesis of nonessential amino acids

Question 5

first phase of amino acid catabolism involves

Answer 5

•transamination -aminotransferase, pyridoxal phosphate
•oxidative deamination
-glutamate dehydrogenase

Question 6

second phase of AA catabolism

Answer 6

• carbon skeletons of alpha keto acids converted to intermediates of
• glycolysis
• krebs cycle

Question 7

excretion of excess nitrogen by humans as non toxic , water soluble urea

Answer 7

ureotelic

Question 8

birds, who excrete uric acid as semisolid guano

Answer 8

uricotelic

Question 9

seen in telostean fish, which excrete highlyy toxic ammonia

Answer 9

ammonotelic

Question 10

Transamination of amino acids

enzyme and coenzyme

Answer 10

enzyme: aminotransferase
coenzyme: pyridoxal phosphate

Question 11

all amino acids transfer their alpha amino group to alpha ketoglutarate –> glutamate
EXCEPT

Answer 11

Lysine
Threonine
Proline
Hydroxyproline

KTP + Hyp

Question 12

2. oxidative deamination of glutamate

Answer 12

L-glutamate –> alpha ketoglutarate
+ NH3
(glutamate dehydrogenase)
to release ammonia

Question 13

glutamate +ammonia

requires this enzyme

Answer 13

glutamine synthase

Question 14

glutamine is deaminated to release ammonia in 2 organs

and through what enzyme

Answer 14

liver - high protein intake
kidneys - response to metabolic acidosis

enzyme: glutaminase

Question 15

In muscle, ammonia is released through

Answer 15

pyruvate transaminated to alanine

alanine -> liver -> pyruvate