Amino Acids Flashcards
What enzyme is used to transform L-arginine to L-ornithine?
Arginase
What is the byproduct of this reactions?
L-Arginine to L-Ornithine
UREA
to what location is urea transported to be excreted?
the kidneys
How many molecules of Nitrogen does urea have?
two
one from Aspartate and one from free NH3
What is the precursor for both NH3 and Aspartate?
Glutamate
What conversion of glutamate gives off NH3?
conversion to alpha KG
What happens to amino acids go if there is low energy?
the amino acid is oxidized to recreate ATP
What happens to AA if low glucose?
the AA is sent to the liver to turn into glucose
What happens to AA’s if we have high energy charge and lots of glucose?
the aa is sent to the liver and turned into fat
Exercise can oxidize specific AA’s to make ATP because of what condition made during exercise?
low energy charge
How are proteins sent to the Liver?
they are sent to the liver on Alanine
What AA’s are able to be oxidized in the Krebs cycle?
LIV GAA (GALIVA)
What enzyme is used for Anaplerosis?
Alpha-ketoglutarate
What enzyme is used in the following reaction: pyruvate +glutamate —> Alanine + alpha-ketoglutarate
ALT
What are the plasma trends when exercising?
Gluatamate concentration decreases
Alanine concentrations increase
What is the ATP turnover when exercising compared to normal?
it increases 100 fold
What is the increase in AA turnover during exercise in muscle?
4-10 fold increase
What does fast glycolysis produce?
extra pyruvate to pick up the amino groups from the amino acids being oxidized in muscle
This is the reason for increased alanine
what is the source for exporting amino acids in muscle glycogen?
pyruvate
What do muscles use branched chain amino acids for?
for fuel
use their nitrogen to make glutamine for export
what do muscle and other tissue’s (except the liver) contain to deal with branched chain aa?
branch chain aminotransferase
what amino acids does muscle take up after a meal?
90% of LIV and glutamate
Does the gut have a large uptake of BCAA?
No, it lacks sensitivity
What area constantly releases glutamate?
splanchnic area
What does the splanchnic area to?
take glutamine and coverts it into gluatmate
What AA’s are released in higher quantities than taken in by muscle?
Alanine and glutamine
How do we turn an AA into fat?
- turn aa into alpha-ketoacid
- turn the alpha-ketoaid into acetyl CoA
- make fat (from acetyl CoA)
What enzyme is used to transform Arginiosuccinate into L-arginine?
Arginiosuccinate Lyase
what are the 3 metabolic circumstances where we break down amino acids?
- protein turnover
- protein rich diet
- Starvation, uncontrolled diabetes melltus
Are amino acids stored in the body?
No
How do we get amino acids?
dietary
synthesized
protein degradation
What is done to excess amino acids?
they are catabolized
What are the steps in catabolism of amino acids?
step 1) removal of amino group
step 2) carbon skeleton
What does oxidation of amino acids mean?
to burn them in the aerobic system (krebs cycle and ETS) to get ATP
When are amino acids oxidized?
when the cell’s energy charge is low
How many amino acids can the liver oxidize?
most of the 20 amino acids
Where are free amino acids pooled?
in cells, blood and extracellular fluid
How is the pool of free amino acids supplied?
by breakdown of endogenous protein, dietary protein and synthesis of non-essential AA.
What is the size of the AA pool in a 70 kg person?
100-200 grams of AA (compared to 12Kg of proteins)
What happens to an amino acid if there is a low energy charge?
the amino acid is oxidized to recreate ATP
what happens to the AA if there is low glucose?
the AA is sent to the liver to turn into glucose
What happens to the AA if there is high energy charge and lots of glucose?
The AA i sent to the liver and turned into fat
What enzyme is used to remove the amino group in an AA?
Aminotransferase (aka: transaminases)
When the enzyme aminotransferase removes the amino group from an AA where is the amino group transferred to?
to alpha-ketoglutarate
What molecule is the excretion pathway of nitrogen?
Glutamate
Is glutamate an amino group donor in the biosynthetic pathway?
yes
What is the 1st step in amino acid metabolism?
Remove amino group and transfer to alpha-ketoglutarate
Where do most amino acids transfer their alpha-amino group to?
to alpha-ketoglutarate
What is the required coenzyme for transamination?
pyridoxal phosphate (a derivative of vitamin B6)
What is the primary site for uptake of most amino acids following a meal?
the liver (50-65%)
What percentage of the amino acids are used for the synthesize of protein in the liver?
20 percent are used for protein synthesis. Most stays in the liver while the rest are released into the plasma
What process removes the amino group from the AA?
Amino acid catabolism
What is left when the amino group is removed from an AA?
an alpha-ketoacid
What is the usual pathway for alpha-ketoacids?
usually enter metabolic pathways (krebs, gluconeogenesis, fat synthesis. . .)
Where are most of the AA metabolized?
the liver
Where is ammonia from extrahepatic tissue transported?
to the liver or excreted
What transport Ammonia to the liver?
Glutamine and Alanine
What are the factors that affects what happens to an alpha-ketoacid?
Energy charge Hormones (glucagon/insulin) respiratory quotient glucose concentration Tissue (liver versus muscle)
The alpha-ketoacid Oxaloacetate can be turned into two other molecules?
Aspartate and Asparagine
Which two AA will not be turned into glucose?
Leucine and Lysine
When blood glucose is low, muscle export what for GNG?
Amino Acids
What is the Glucose Alanine cycle that occurs during exercise?
- muscle is releasing alanine during exercise
- liver turns Alanine into glucose
- Liver takes the amino group and converts it to urea
How are amino acids turned into fat?
- turn the amino acid into an Alpha-ketoacid
- Turn the alpha-ketoacid into acetyl CoA
- Make Fat (Use: Acetyl CoA Carboxylase and Fatty Acid synthase)
What are the two ketogenic only AA?
Leucine and Lysine
