Lecture 33 - Amino Acid Metabolism I Flashcards
Degradation and re-synthesis of proteins.
protein turnover
These are organelles that are important in protein turnover. They physically degrade proteins, usually by means of acidification or peroxide.
A. proteosome
B. ubiquitin
C. lysozome
D. hydrolase
C. lysozome
These act as a molecular “garbage can” and degrade proteins that have been marked by molecular “tags.”
A. proteosome
B. ubiquitin
C. lysozome
D. hydrolase
A. proteosome
The urea cycle is important in the removal of _____ from blood.
a. nitrogenous compounds
b. amino acids
c. amino groups
c. amino groups
Removal of the ammonium group from an amino acid occurs via a two step process. Step 1 is the transfer of the NH3 to ______.
glutamate (deamination)
Step 2 of amino acid metabolism is the ___________
release of NH4 (ammonium) from glutamate (dehydrogenation)
_____ is required to accept the NH3 from glutamate
A. Vitamin B6 (pyridoxine)
B. Vitamin B3
C. NAD
B. B3
________ is required to accept the NH3 from amino acids.
A. Vitamin B6 (pyridoxine)
B. Vitamin B3
C. NAD
A. Vitamin B6 (pyridoxine)
____ serves as a co-factor to cleave NH3 from glutamate.
A. Vitamin B6 (pyridoxine)
B. Vitamin B3
C. NAD
C. NAD
The reaction removing NH3 from glutamate occurs in ____.
A. muscle
B. brain
C. liver
C. liver
produces urea
DRAW THE UREA CYCLE.
Check your drawing
Citrulline + Asp = _______________
argininosuccinate
argininosuccinate is degraded to _____________
fumarate
A patient presents with large amounts of ornithine in the blood. What enzyme is most likely deficient?
ornithine transcarbamoylase
A patient presents with elevated arginine levels. What enzyme is deficient?
argininase I
A patient would except to have low levels of fumarate in what enzyme deficiency?
argininosuccinate lyase
A patient would have large amounts of aspartate in what enzyme deficiency?
Argininosuccinate synthetase (uses aspartate and citrulline to form argininosuccinate)
From what source does urea obtain its nitrogen?
ammonium and aspartate
from what source does urea obtain its carbon?
CO2
The product of the arginine to ornithine reaction in the urea cycle can be used as a measurement of liver function. What is the product and what is the test?
urea; blood urea nitrogen
Explain why NH4+ is toxic to the nervous system?
In order to remove excess NH4 from the nervous system, the urea cycle must be run almost continuously. This results in decreased NADPH, decreased alpha-ketogluterate (a TCA intermediate), and decreased ATP.
This has the overall effect of “de-energizing” the brain.
What amino acid is primarily used in transporting NH4 in the brain?
Glutamine
What AA is used to transport NH4 in the liver?
Alanine
What two enzymes are solely ketogenic?
lysine and leucine
Following the removal of NH3 from proteins, the _________ may be used as fuel molecules.
A. carbon skeletons
B. carbonyl
C. carboxylic acid group
A. carbon skeletons
What is the mechanism behind NS damage in hyperammonemia?
Defects in the urea cycle produce large amounts of urea.
This will inactivate the neuronal Na/K/Cl ATPase pumps, changing cellular osmolarity.
This osmolarity change results in the swelling/rupture of neurons.
Solely ketogenic AAs
Lysine (K)
Leucine (L)
Both ketogenic and glycogenic AAs
Frank, will you interpret?
F- phenylalanine
W-Twyptophan
Y-tYrosine
I-Isoleucine
