Urea cycle and nitrogen metabolism

Question 1

Where does ammonia come from?

Answer 1

intracellular amino-acid turn over
Dietary protein

Question 2

what happens if ammonia builds up?

Answer 2

hyperammonemia
damages brain cells => abnormal behaviour, dizziness, coma and death

Question 3

What conditions cause hyperammonemia

Answer 3

Liver dysfunction
Abnormality in hepatic portal flow
abnormality in urea cycle enzymes
starvation (body breads down skeletal muscle for energy -> more amino acid catabolism)

Question 4

Generally describe the Kreb’s/TCA/Citric acid cycle

Answer 4

Acetyl-CoA converted by a series of enzymes into CO2, water, and ATP

Question 5

What is oxidative deamination?

Answer 5

removal of an amino group from an amino acid or compound => produces ammonia

Question 6

What is transamination?

Answer 6

amino acid transfer between compounds to create a new molecule

Question 7

Label the urea cycle

Answer 7

Question 8

Describe the process of deamination

Answer 8

a-amino acid + a-keto glutarate <=> a-keto acid + glutamate

Question 9

How is excess ammonia removed in the absence of amino acids?

Answer 9

formation of glutamate and glutamine from a-ketoglutarate

Question 10

What is the fate of a-keto acids (product of deamination)?

Answer 10

recycled into the TCA/Kreb’s/Citric acid cycle or used in lipid metabolism
Ketogenic amino acids - will feed lipid metabolism
Glucogenic amino acids will feeds gluconeogenesis

Question 11

Label the urea cycle

Answer 11