Amino Acid Metabolism Flashcards
Two parts to amino acid metabolism
1) Maintenance of amino acid pools in cells and blood plasma
2) The use as nutrients
Why is the transaminse reaction so important for amino acid metabolism?
The transaminase reaction allows channelling of amino-groups into particular amino acids such as alanine, aspartate and glutamate. All three can easily be metabolised by the liver and amino-groups be disposed of as urea.
What vitamin is essential to amino acid transaminase?
Pyridoxalphosphate (Vitamin B6)
What is a glucogenic and a ketogenic amino acid?
A glucogenic amino acid is metabolised into compounds that can be converted into glucose. A ketogenic amino acid is converted into acetyl-CoA, which cannot be used to generate glucose.
What is phenylketonuria?
Phenylketonuria is a rare inborn error of metabolism. Its caused by mutations of phenylalanine hydroxylase. In PKU plasma levels of phenylalanine are highly elevated, resulting in amino acid imbalance in the brain. This causes imbalances of neurotransmitters, causing mental retardation if untreated.
Role of stomach in protein digestion
Pepsin and acidity break down complete proteins into smaller parts.
Role of pancreas in protein digestion
Stores four kinds of enzymes for protein fragments to be broken down into oligopeptides (2-20 amino acids).
Enzymes in pancreas
Trypsin, chymotrypsin, elastase and carboxypeptidase
Role of brush-border enzymes
To break down oligopeptides into amino acids, dipeptides and tripeptides
How is the pancreas not digested by its own enzymes
The proteins are stored as pro-enzymes (zymogens) which need to be partially hydrolysed to become active.
Where are amino acids filtered?
In the kidney
What is the role of the kidney tubule in maintaining nutrient, water and ion levels?
The kidney tubule is the place where individual components of the primary urine (formed in the glomerulus) are recaptured. In the proximal tubule all nutrients are reabsorbed and returned to the blood. Water and ions are absorbed all along the tubule.
Where is the urea cycle?
The liver
Role of ornithine
Transports out ammonia for the urea cycle
Role of tetrahydrofolate
Cofactor for amino acid and nucleic acid synthesis. It is turned into formate, which constitutes two carbons of the purine rings.
