Hepatic Protein Metabolism and AA in Nitrogen Balance

Question 1

How do AA get absorbed into the blood?

Answer 1

Passive Diffusion

Question 2

What fuels does the liver use?

Answer 2

Glucose, amino acids, fatty acids

Question 3

Role of endo and exopeptidases?

Answer 3

Endo: Break peptide bonds between non-terminal AA
Exo: Break peptide bonds between terminal AA and form monomers

Question 4

What is transamination?

What is catalyst?

Answer 4

Transfer of alpha-amino group from AA to keto-acid

Catalyst: Aminotransferases (Cytosol and Mitochondria)

Question 5

What is anabolic nitrogen balance?

Answer 5

Positive balance, nitrogen intake greater than loss

Question 6

Transamination products?

Answer 6

Alpha-keto acid that can go on to KC and glutamate

Question 7

Describe oxidative deamination and its catalyst

Answer 7

AA catabolism, results in amino group liberation as free NHS

Glutamate Dehydrogenase

Question 8

Describe nitrogen balance?

Answer 8

Measure of equilibrium of protein turnover (intake-loss)

Question 9

Average nitrogen intake?

Answer 9

0.8g/Kg body weight

Question 10

What’s the glucose-alanine cycle?

Answer 10

Series of reactions where Amino groups and carbons from muscle transported to the liver

Question 11

G-A cycle: What reactions take place in muscle?

Answer 11

Glucose –> Pyruvate (Glycolysis)

Pyruvate –> Alanine (Transamination)

Question 12

G-A cycle: What reactions take place in liver?

Answer 12

Alanine –> Pyruvate (Oxidative Deamination)
NH3 goes onto the Urea cycle
(Pyruvate into glucose via gluconeogenesis)