Ch 18 Nitrogen Metabolism Flashcards
(23 cards)
What is the process of nitrogen fixation in legumes?
Nitrogen fixation into NH3 happens in the root nodules of legumes like soybean and redbud trees.
Where does nitrogen fixation also occur aside from legumes?
In marine bacteria called cyanobacteria.
What type of environment do root nodules create for nitrogen fixation?
Anaerobic environment.
What is the overall reaction catalyzed by nitrogenase?
N2 + 8 H+ + 8 e− + 16 MgATP → 2 NH3 + H2 + 16 MgADP + 16 Pi.
Why is ammonia assimilated into useful compounds?
Ammonia is toxic at high concentrations.
Which amino acids are formed from ammonia?
- Glutamate
- Glutamine.
How is glutamate formed from α-ketoglutarate?
By reductive amination catalyzed by glutamate dehydrogenase.
What enzyme converts glutamate to glutamine?
Glutamine synthetase.
What is the importance of transaminases?
They help diagnose serious liver disease and heart attacks.
What do transamination reactions transfer?
An amino group from one amino acid to an α-keto acid.
What are the products of transamination reactions?
- New amino acid
- α-keto acid.
What is the role of pyridoxal phosphate (PLP) in transamination?
PLP is covalently attached to the transaminase and holds the amino acid.
What is the fate of carbon skeletons in amino acid metabolism?
They can follow glucogenic or ketogenic pathways.
What are glucogenic amino acids catabolized to?
Pyruvate or oxaloacetate.
What are ketogenic amino acids catabolized to?
Acetyl-CoA or acetoacetyl-CoA.
What is a precursor of serotonin?
Tryptophan.
What cycle produces urea?
The urea cycle.
Where does the urea cycle occur?
In the liver.
What is the main nitrogen source for the urea cycle?
- Ammonia
- Aspartate.
What is carbamoyl phosphate used for in the urea cycle?
It is an amino group acceptor/donor.
Name the intermediate formed when citrulline is exported to the cytoplasm.
Citrullyl-AMP.
What happens to argininosuccinate in the urea cycle?
It is cleaved to arginine and fumarate.
What two products are formed when arginine is cleaved?
- Urea
- Ornithine.
