Protein and amino acid metabolism Flashcards
Give an example of a glucogenic amino acid.
Alanine
Give an example of a ketogenic amino acid.
Lysine
Give an example of an amino acid that is both glucogenic and ketogenic.
Tryptophan
What effect does insulin have on protein synthesis?
It increases protein synthesis
What effect does glucocorticoids such as cortisol have on protein synthesis?
It deceases protein synthesis
Why can Cushing’s syndrome lead to striae?
There is excess cortisol stimulating excessive protein breakdown
Glutamate is a precursor for …….
GABA
Tryptophan is a precursor for serotonin. True or false?
True
What are the two main pathways to facilitate nitrogen removal?
Transamination and deamination
All aminotransferases are a derivative of vitamin ….
Vitamin B6
Which enzyme uses oxaloacetate as a substrate instead of a-ketoglutarate? (Transamination)
Aspartate aminotransferase
What is the name of the two key aminotransferases associated with liver function? And what is their role?
Alanine aminotransferase (ALT)- Converts alanine to glutamate Aspartate aminotransferase (AST)- Converts glutamate to aspartate
Where does deamination occur?
The liver and the kidney
Which two amino acids can enter the urea cycle?
Glutamate and aspartate
Is the urea cycle regulated?
No. It is inducible but not regulated.
What is a glucogenic amino acids?
Amino acids that can be converted to glucose via gluconeogenesis
What are ketogenic amino acids?
Amino acids that can be degraded directly into acetyl CoA which is the precursor of ketone bodies.
What causes refeeding syndrome?
Ammonia toxicity due to the down-regulation of the urea cycle
Defects in the urea cycle leads to what?
Hyperammonia and accumulation/excretion of urea cycle intermediates
What are the symptoms of hyperammonemia?
Vomiting, lethargy and irritability
Which organ is ammonia very toxic to and why is it toxic?
It is toxic to the brain and disrupts cerebral blood flow as well as altering the blood-brain barrier.
Ammonia can combine with which amino acid to move from the periphery to the liver or kidney for disposal?
Glutamate. It combines with glutamate to form glutamine via Glutamine synthase.
Which enzyme is deficient in PKU?
Phenylalanine hydroxylase
What accumulates in PKU and how is it excreted?
Phenylalanine accumulates and phenylketones are consequently seen in the urine
