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Lecture 31

Urea Cycle and NO synthesis

What carbon sources can be broken down for energy? Carbohydrates, proteins, and fatty acids
What are the sources for amino acids for energy generation in the body? Dietary protein
What organs don't use amino acids for energy? Brain and the Red blood cells
What two amino acids specifically breakdown to form Acetyl-CoA? Lysine and Leucine
What three amino acids can be used in the liver to make glucose? Alanine, aspartate, and glutamate
What are two fates of an alpha keto acid? Kreb's cycle or gluconeogenesis
What enzyme transfers the amine from amino acids in the muscle to pyruvate? What are the products? Co-factor? Pyruvate + Glutamate --> Alanine and A-ketoglutarate; Alanine aminotransferase; PLP
How does alanine get to the liver? Travels in the blood
What is Alanine the amino acid that travels in the blood? Alanine is a stable molecule. Free ammonia is too toxic and other amino acids are more reactive
What amino acid releases ammonia in the muscle? Glutamate
What does ALT stand for? Alanine aminotransferase
What reaction does ALT catalyze? The transamination from alanine to glutamate
Why is alanine converted to glutamate in the liver? Glutamate carries the free amine which is later released to the urea cycle
What are two fates for glutamate in the liver? It can enter the citric acid cycle through alpha keto glutarate or it can do transamination with OAA to form Aspartate which enters the urea cycle
What are two types of amines that enter into the urea cycle? The amine from aspartate and the amine from glutamate
What is the carbon backbone that free ammonia attaches to? Bicarbonate- HCO3
What is the first molecule that enters the urea cycle? Why does it take 2 ATPs to form this product? Carbomoyl phosphate; it takes 1 ATP to do the reaction and 1 ATP to phosphorylate it
Where does the amine from aspartate enter the urea cycle? After the citrulline intermediate
What carbon skeleton is released by the urea cycle and enters the citric acid cycle? Fumarate
What amino acid is synthesized in the urea cycle? Arginine
Where do the two amines and the carbonyl of urea originate from? the two amines come from aspartate and glutamate; the carbonyl comes from bicarbonate
What are the substrates, source of oxygen and products of NO synthesis? Substrate(arginine and NADPH)Products(NADP+, Citrulline, and NO)
What second messenger is increased in the presence of NO? cGMP
What affect does cGMP have on blood vessels? Relaxes smooth muscles and increases vasodilation
What enzyme cleaves cGMP to form 5' GMP? cGMP phosphodiesterase
What happens to the NO formed in the endothelial cell? It leaves the endothelial cell and enters the smooth muscle to affect guanylyl cyclase
What reaction does guanylyl cyclase catalyze? GTP to cGMP
What does viagra do? Inhibits the penile form of PDE so cGMP levels stay high
Created by: bettyboucher