L29 - Nitrogen Metabolsim 2 Flashcards
What is transamination?
The process by which -NH2 is transferred from an amino acid to a keto-acid to form a new amino acid
What amino acid does ammonia assimilation change nitrogen into?
Glutamate
What are 2 kinds of enzyme that catalyse transamination called?
Transaminases and Aminotransferase
What compound acts as a coenzyme to transfer the -NH2 group?
Pyridoxal Phosphate (PP)
What does transamination allow?
allows plants and some micro-organisms
When glutamate reacts with keto-acids with the R groups following, which amino acid does it create?
a) -CH3 (Pyruvate)
b) -CH2OH (3-phosphoglycerate)
c) -CH2COOH (oxaloacetate)
a) Alanine
b) Serine
c) Aspartate
What is the source of keto-acids for amino acid synthesis?
Intermediates of carbohydrate and lipid metabolism
If some enzymes that are necessary to make some of the AAs where are they gained from? What are these called?
Those amino acids have to be supplied in the diet or growth medium
They are called essential or indispensable AAs
Name the essential amino acids for humans for each category:
a) Basic AAs
b) Branch chain AAs
c) Aromatic AAs
d) Others
a) Arginine, Lysine, Histidine
b) Leucine, Isoleucine, Valine
c) Tyrosine, Tryptophan, Phenylalanine
d) Methionine, Threonine
Can excess amino acids taken in in the diet be stored for later?
No - they are degraded
Name and describe the 2 stages of AA degradation
1) Deamination
- opposite of transamination
- NH2 group is transferred from the AA to 2-oxo-glutarate to form glutamate
2) Oxidative deamination
- reverse of ammonia assimilation
- the NH2 group of glutamate is removed by glutamate dehydrogenase
The keto acids formed during deamination feed into the central metabolic pathways. What happens to each:
a) glycogenic keto acids
b) ketogenic keto acids
a) they can be used as a substrate for glucose synthesis
b) they can be used to synthesise ketone bodies
The NH3 formed by oxidative deamination is potentially toxic to animals, what do most to do get rid of it? How are birds, most reptiles and fish different?
Convert it to urea, as then it can be excreted through the kidneys as urine.
Birds and most reptiles excrete uric acid
Fish excrete ammonia
Where does the first part of the process of getting rid of NH3 take place?
In mitochondria and requires 2ATP
What enzyme is needed for the first step of getting rid of NH3 and what does it convert into what?
Carbamoyl phosphate synthetase
Converts:
bicarbonate + ammonia —> carbamoyl phosphate
requiring 2ATP
