E4 Amino Acid Metabolism Flashcards
what 4 groups are attached to a carbon to make an amino acid?
hydrogen, amine group (NH2), hydroxyl group (COOH), and R group
T/F. the diet is an important source of amino acids.
true
when we get amino acids through our diet, what are they absorbed by and where are they sent?
absorbed- by intestine
sent to- the blood
T/F. most proteins are short-lived.
true
can we store amino acids like we do glucose (glycogen) or fatty acids (TAGs)? why or why not?
NO
if we are not using it, we break it down (catabolism)
where in the body will you find free amino acids? (amino acid pool)
cells, blood, extracellular fluid
the amino acid pool is supplied by the breakdown of what three things?
- endogenous protein
- dietary protein
- synthesis of non-essential aa
if we are not using the aa to build larger proteins, we break it down. what we convert it into depends on what two things?
- which aa it is
2. what tissue we are in
what is the primary location for most of our aa breakdown?
liver
after a meal, the liver gets majority of the aa from the _________.
portal blood
T/F. after a meal, the liver gets most of the aa from the portal blood. once the aa reach the liver, some stay in the liver and most are released into the blood.
false; most stay in the liver while the rest are released into the blood
what type of aa are an exception and are used more by skeletal muscle and the heart rather than the liver?
branched chain amino acids
T/F. Most of the ATP production in the liver is from FA oxidation.
false; from aa oxidation
skeletal muscle is only able to significantly oxidize 6 amino acids. name them.
- leucine
- isoleucine
- valine
- glutamate
- aspartate
- asparagine
(LIV GAA)
of the six amino acids that are oxidized by skeletal muscle, which ones are branched chain amino acids?
leucine, isoleucine, and valine
LIV
if an aa loses an amino group, what does it become?
alpha ketoacid
if alanine loses an amino group, what does it become?
pyruvate
T/F. alpha ketoacids have no amino groups.
true
if an alpha keotacid gains an amino group, what does it become?
(alpha) amino acid
define transamination.
transfer of an amino group from one amino acid to an alpha ketoacid
if an amino group (N) is transferred to an alpha ketoglutarate, what does it become?
glutamate
define deamination.
removal of an amino group from an amino acid
if an amino group is removed from an aa, what are the products?
alpha ketoacid and an ammonium ion
T/F. transamination can occur in many tissues.
true
what enzyme is associated with transferring an amino group from one amino acid to an alpha ketoacid? does it require a coezyme?
aminotransferase/transaminases
coezyme: pyridoxal phosphate
what is the common amino group acceptor?
alpha-ketoglutarate
when aminotransferases are involved in transamination, is the reaction reversible?
yes
what enzymes are associated with deamination?
lyases, dehydratases, or dehydrogenases
oxidative deamination of glutamate in the liver provides nitrogen for what cycle?
urea cycle
what are the reactants and products of glutamate dehydrogenase?
R: NAD+ and glutamate
P: NADH, NH4, alpha ketoglutarate
what type of reaction is glutamate dehydrogenase involved in?
redox reactions
match the alpha ketoacid to the aa.
A. alanine
B. glutamate
C. aspartate
D. glutamine
- alpha ketoglutarate
- oxaloacetate
- pyruvate
A. 3
B. 1
C. 2
D. 1
alpha ketoglutarate + 1N= _______
alpha ketoglutarate + 2N= ________
1- glutamate
2- glutamine
T/F. Glutamate is important in transporting amino groups to and from peripheral tissues.
false; glutamine
what enzyme is responsible for oxidative deamination and will produce ammonium for excretion via urea cycle?
glutamate DH
what enzyme adds an amino group to glutamate to become glutamine?
glutamine synthetase
what enzyme removes an amino group from glutamine to become glutamate?
glutaminase
T/F. glutamate DH will remove an amino group from glutamine while glutaminase will remove an amino group completely.
false; glutamate DH will remove amino group completely
glutamine comes from glutamate via which enzyme?
glutamine synthetase
glutamate comes from glutamine via which enzyme?
glutaminase
what enzyme is responsible for the following reaction?
alanine pyruvate
alanine aminotransferase (ALT)
aka
glutamate-pyruvate transaminase (GPT)
what are the steps in the muscle for ALT/GPT?
- aa oxidized
- transfer the amino group to alpha ketoglutarate
- becomes glutamate
- amino group is then transferred to pyruvate
- becomes alanine
- alanine sent to liver via blood
what are the steps in the liver for ALT/GPT?
- amino group transferred from alanine to alpha ketoglutarate
- pyruvate can enter GNG
- pyruvate converted to glucose
- glucose sent to muscle
oxaloacetate + 1N= ________
oxaloacetate + 2N=________
1- aspartate
2- asparagine
what enzyme is responsible for transferring an amino group from glutamate to oxaloacetate to produce aspartate?
aspartate aminotransferase (AST)
aka
glutamate-oxaloacetate transaminase (GOT)
glutamate + oaa –> alpha ketoglutarate + aspartate
is an important rxn for three reasons. name them.
- provides N for nucleotide synthesis
- provides N for urea cycle
- malate-aspartate shuttle
T/F. when we remove the amino group, the alpha ketoacid is left and can be converted into metabolic intermediates depending on the need of the cell.
true
in amino acid metabolism we have removed the amino group. what do we do with the nitrogen??
use it or excrete it
aspartate is being catabolized. what enzyme do we need and what is the rxn?
aspartate aminotransferase (AST)/(GOT)
aspartate + alpha ketoglutate oaa + glutamate
alanine is being catabolized. what enzyme do we need and what is the rxn?
alanine aminotransferase (ALT)/(GPT)
alanine + alpha ketoglutarate pyruvate + glutamate
oxidative deamination of glutamate.
what enzyme do we need and what is the rxn?
glutamate DH
glutamate + NAD+(NADP+) –> alpha ketoglutarate + NADH + NH4+
what is a unique feature about the reaction that uses glutamate DH?
it can use either NAD+ or NADP+
what are two other amino acids that can be directly deaminated? what enzymes do they require?
threonine - threonine dehydratase
serine - serine dehydratase
what are the products of threonine dehydratase?
alpha ketobutyrate and NH4+
what are the products of serine dehydratase?
pyruvate and NH4+
T/F. the liver can breakdown all amino acids.
false; most aa’s except branched chain (LIV)
what two amino acids will transport out the amino group from peripheral tissues?
alanine and glutamine
T/F. the reaction that uses glutamine synthetase is energy producing.
false; energy requiring
R: glutamate + NH4+ + ATP
P: glutamine + ADP
glutamine can transport the amino groups to what two places?
- the liver for excretion
2. tissues that need it
the ammonium ion (NH4+) we are not using needs to be excreted as _____ because it is toxic.
urea
what is the tissue location for the urea cycle? cell location?
tissue- liver
cell- matrix and cytosol
where do we get the nitrogen that will be excreted as urea?
- free NH4+ (glutamate DH)
[R: NAD+ and glutamate
P: NADH, NH4, alpha ketoglutarate] - transferred rom aspartate
where do we get the carbon for the urea molecule?
HCO3- (bicarbonate)/hydration of CO2
what are the 4 intermediates of the urea cycle that we need to know?
- ornithine
- citrulline
- argininosuccinate
- arginine
what is the first and important step of the urea cycle?
produce carbamoyl phosphate
what is the location where carbamoyl phosphate is produced?
matrix
what enzyme is responsible for producing carbamoyl phosphate?
carbamoyl phosphate synthetase I (carbamoyl phosphatase)
T/F. the urea cycle is energy requiring and uses 2 ATP.
true
what is the key regulatory step of the urea cycle?
carbamoyl phosphatase
what are the reactants of carbamoyl phosphatase?
HCO3- + NH3 + 2 ATP
where do we get the 1st nitrogen that enters the urea cycle?
deamination of glutamate
in the allosteric regulation of the urea cycle, what is the main regulator?
N-acetylglutamate (NAG)
T/F. N-acetylglutamate (NAG) is activated in the presence of decreased amino acids.
false; increased amino acids
what are the two amino acids that will help activate NAG?
arginine and glutamate
once carbaoyl phosphate is made, it will be a reactant with what intermediate to produce L-citrulline?
L-ornithine
carbamoyl and L-ornithine will produce _______ and ______.
L-citrulline and Pi
L-citrulline along with ATP and what amino acid will produce argininosuccine?
aspartate
L-citrulline + ATP + aspartate will produce ______, ______, and ______.
argininosuccinate, AMP, Pi
argininosuccinate will become ______ and produce ______.
L-arginine; fumarate
when argininosuccinate becomes L-arginine, where does the fumarate that is produced go?
Krebs
L-arginine –> L-ornithine
what enzyme is responsible?
arginase
what are the reactants and products of arginase?
R: L-arginine
P: L-ornithine
T/F. when L-ornithine becomes L-arginine; urea is released.
false; L-arginine becomes L-ornithine via arginase= urea released
where is urea transported to to be excreted?
to the kidneys via blood
T/F. some ammonia diffuses back into the blood and is sent to GI and excreted in feces.
true
define hyperammonemia.
elevated level of NH4+
what are two ways to get hyperammonemia?
- genetic
2. alcohol consumption
define genetic hyperammonemia.
1 in 15,000 births
can lead to coma, brain damage
what happens if you have excessive alcohol consumption and get hyperammonemia?
cirrhosis
liver cannot convert ammonia to urea
