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How are carbohydrates and fats stored in our body?
Carbohydrates stored as Glucogen
Fats are stored as Triacylglycerol
What is the metobolic fate of amino acids?
Use it or convert it to urea and eliminate it.
If it is stored, it becomes a toxic storage form.
What is the name of the enzymes that process the urea in the liver?
Urea is synthesized in the liver by the enzymes of the UREA CYCLE
What is the overall fate of amino acids?
Notice the link between the urea cycle and citric acid cycle.
In order to have a constant development of ATP, all the intermediates of the citric acid cycle need to be maintained.
What is the fate of the nitrogen skeleton of an amino acid when it is degraded oxidatively?
Metabolized and used in the citric acid cycle to synthesize glucose
What intermediate of the urea cycle is produced as a byproduct that can be supplied to the citric acid cycle?
Fumaric acid (Fumarate) - This will help fill any gaps in the citric acid cycle.
What is the name of the shunt pathway that links the urea cycle to the citric acid cycle?
The Asparatate-arginino-succinate shunt
Describe transamination reaction. Give an example including the enzyme catalyzing the reaction and the cofactor used.
Requires pyridoxal phosphate (Vitamin B6) as cofactor
α-Amino groups are converted to NH4+ ion by which process and enzyme?
Oxidative Deamination of Glutamate - Removal of amine group
Glutamate dehydrogenase - An oxidizing enzyme.
How is the ammonia group transported in the bloodstream?
Ammonia is Transported in the Bloodstream Safely as Glutamine and Alanine as its carriers and then finally into the Liver
What are the two enzymes needed to synthesize and break down glutamine?
Glutamine synthetase - two steps to form Glutamine from Glutamate.
Glutaminase - Converts Glutamine back to Glutamate
What enzyme converts Pyruvate to Alanine?
Alanine aminotransferase - This happens in the live tissue
What are Alanine an Glutamine converted to once they arrive into the liver?
Back to Glutamate
Alanine uses Glutamate Pyruvate Transaminase Enzyme
Glutamine uses Glutaminase Enzyme
NH₄⁺ is converted to Carbamoyl phosphate in Mitochondria by what enzyme?
Carbamoyl phosphate synthetase I - Rate Limiting Step
CPS I for Urea Biosyntheses
Which two amino acids are the carriers of amino acid nitrogen from the muscle and other tissues to the liver?
Alanine an Glutamine
Why it is necessary to convert glutamate to alanine and glutamine?
Because glutamate cannot cross the membrane; therefore, glutamate is converted to alanine and glutamine because they can cross the membrane.
Which enzyme is required to regenerate glutamate from alanine in liver tissue?
At which cellular site the rate-limiting enzyme of the urea cycle is localized?
Mitrochondria - Carbamoyl phosphate synthetase I
How is Carbamoyl phosphate synthetase I (CPS-I) regulated?
CPS-I is activated by N-Acetyl Glutamate (NAG).
CPS-I is a Allosteric actitvator.
Arginine stimulates NAG synthesis
How bicarbonate used to form carbamoyl phosphate is activated in urea cycle reaction?
ATP - it activates the bicarbonate in the first step.
What happens during the second reaction in the first nitrogen-acquiring reaction?
Carbamate is formed by ammonia displacing phosphorly group.
What happens during the third reaction in the first nitrogen-acquiring reaction?
Carbamate is phsophorylated to to yield carbamoyl phosphate
Which intermediate is produced when ATP and bicarbonate react before ammonium ion is captured in the first reaction of urea cycle?
How many molecules of ATPs are required to produce carbamoyl phosphate in the first priming reaction of urea cycle?
Nitrogen from Carbamoyl Phosphate Enters the Urea Cycle via formation of what amino acid?
What amino acid is used as a substrate to form Citrulline?
Ornithine - Carbamoyl Phosphate is also a substrate
Once in the cytosol, what is the second nitrogen-acquiring reaction?
Argininosuccinate synthetase condenses citrulline with aspatate
What enzyme releases urea?
Arginase catayzes the hydrolysis of arginine to produce Urea and regenerate ornithine in cytosol.
What links the urea cycle and citric acid cycle?
Aspartate -Arginosuccinate Shunt
Fummarate which is fed back into the citric acid cycle. This links the citric acid cycle with the urea cycle.
How is the urea cycle regulated in regards to Substrate availability?
High rate of NH3 production, high rate of urea production
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