Week 7 - Protein metabolism Flashcards
What is protein digestion in the stomach initiated by?
Pepsin and hydrochloric acid.
What 2 proteases are secreted in the small intestine?
Pancreatic proteases and enterocyte proteases.
This results in peptide fragments and free amino acids being absorbed by the small intestine.
What % of all amino acids does the gut extract?
40-50%
What % of amino acids (not absorbed by gut) that enter portal vein make it to the muscle?
Only 10-11%
Following ingestion, how is protein source denatured into polypeptides in the stomach?
By the highly acidic environment (pH 1.5-3.5)
Where does dietary protein pass once it has been denatured in the stomach?
Small intestine
What happens to denatured proteins in the small intestine, and what enzyme is this initiated by?
Denatured proteins are neutralised via bicarbonate to a pH 6-9.
This is initiated by secretin which acts on pancreas to secrete bicarbonate.
What happens to denatured proteins after they have been neutralised?
Undergo further degradation via protease enzymes into single amino acids to enter circulation for use as a substrate for energy or protein synthesis.
What is the relationship between muscle protein breakdown and synthesis in a fasted state?
Breakdown > synthesis = negative net balance
What is the relationship between muscle protein breakdown and synthesis in a fed state?
Synthesis > breakdown = positive protein balance
What is transamination?
The transfer of 1 amino group from 1 molecule to another.
What enzyme is transamination catalysed by?
Aminotransferase
What is deamination?
The amino acid removal and loss of its amino group
What toxic product is formed as a result of deamination?
Ammonia - converted into urea in the liver and is excreted by kidneys.
By what process does the liver use its pool of amino acids for glucose synthesis?
Gluconeogenesis.
