Final Flashcards
Unlike fats and carbs there is no _______ _____ for amino acids
storage form
Nitrogen ________ is nitrogen ingested = nitrogen excreted
balance
What are the 3 ways to get amino acids
dietary proteins
de novo synthesis
degradation of cellular proteins (normal turnover)
What is the major stomach protease
pepsin
Protein degradation continues in the lumen of the intestine by _______ proteases
pancreatic
What are the two cellular protein degradation
Lysosomal degradation (no energy, extracellular proteins that are taken into cells by endocytosis)
Proteasomal degradation (requires ATP, mainly endogenous proteins)
Lysosomes contain about ___ hydrolytic enzymes
50
In lysosomal degradation-starving cells, there is a selective pathway that preferentially degrades cytosolic proteins containing the sequence ______
KFERQ
Proteins that are going to be degraded are “tagged” with protein called
ubiquitin (proteasome digests it, it is attached to lysine residues on target proteins)
____ or more ubiquitins have strong signals for degradation
4
What are the 4 fates of amino acids
-can be used for protein synthesis
-if not needed for protein synthesis must be degraded
-first step in amino acid degradation is the removal of the nitrogen
-removed amino group is converted urea in the liver
______ uses its own amino acids as fuel during prolonged exercise and during fasting
muscle
The amino group of the amino acid being degraded is first removed form the _____ ______ being degraded
amino acid
Once the amino acid is removed from the amino acid being degraded, its transferred to ____________ which then becomes __________
alpha-ketoglutarate
glutamate
alpha-ketoglutarate converted to glutamate is catalyzed by what enzyme
aminotransferases
All aminotransferases contain the cofactor
PLP (pyridoxal phosphate)
PLP is derived from what
pyridoxine (Vitamin B6)
The aminotransferase enzymes also have value clinically as _________ agents
diagnostic
What are the 4 clinical values of plasma aminotransferases
-normally intracellular enzymes
-plasma concentration are typically low
-elevated plasma levels = indicate damage to cells rich in these enzymes
-AST and ALT measurements are of particular diagnostic value
What do AST and ALTs test for
liver damage
heart damage
(high plasma levels of both indicate more severe damage)
What is amino acid catabolism
-transamination reaction occurs 1st
-then oxidative deamination to release ammonia which is combined with CO2 to make urea
What is glutamate dehydrogenase
occurs only in liver mitochondria
oxidative deamination and needs an electron acceptor of NAD+
In severely impaired hepatic function and cirrhosis _________ intoxication develop
ammonia
When ammonia concentration increases in blood and other bio fluids, it diffuses across the BBB causing ammonia _____________
encephalopathy