Protein Breakdown And Urea Formation Flashcards
How do proteins enter the body and what are they broken down into?
Food
Amino acids
What is the normal ratio of amino acids:body protein?
50:50
How is the carbon skeleton formed from amino acids?
The nitrogen is taken off
What is the carbon skeleton used for?
Glucose generation
ATP source
Generation of ketone bodies
What happens to the nitrogen that is removed from amino acids?
Broken down in the liver to form urea and is excreted by the kidney
What is positive nitrogen balance?
There is a build up of body proteins- the amino acid pool is directed towards the making of new proteins
When does positive nitrogen balance occur?
During pregnancy or growth
Exercise and tissue hypertrophy (build up of new muscle protein)
Response to anabolic hormones
What is negative nitrogen balance
A loss of body protein which leads to increased urea production
When does negative nitrogen balance occur?
Wasting diseases, burns, trauma
Response to either an increase in catabolic or a reduction in anabolic hormones (diabetes)
What are the two things that happen to amino acids?
Used or broken down- NEVER STORED
What enzymes facilitate the removal of nitrogen?
Transaminase or aminotransferase
What happens in transamination?
Amino acid A + alpha keto acid B-> alpha keto acid A and amino acid B
Basically the NH3 group is transferred from amino acid A to amino acid B
Give some examples of alpha keto acids
Alpha ketoglutarate
Pyruvate
Oxaloacetate
What are two of the most important transaminases?
Alanine (ALT) and aspartate (AST)
What does aspartate + alpha ketoglutarate produce?
Glutamate and oxaloacetate
In the liver what are oxaloacetate and alphaketoglutarate used to make?
Glucose
In muscle, where can pyruvate be used?
In the TCA cycle and ETC to make ATP
Also gluconeogenesis
What is high levels of AST and ALT in the blood indicative of?
Tissue damage- esp in liver and cardiac muscles
What is the enzyme involved in the formation of amonnia?
Glutamate dehydrogenase
What is the formation of ammonia process known as?
Oxidative deamination
Free ammonia + glutamate ->?
Glutamine
What enzyme does the ammonia + glutamate reaction use?
Glutamine synthase
How is AA nitrogen transferred to urea (3steps)?
Transamination, formation of ammonia. Synthesis of urea
Where does the urea cycle take place?
Mitochondria and cytoplasm
What are the substrates for the urea cycle?
Bicarbonate, aspartate and ammonium ions
CO2+ NH4 ->?
Carbonyl phosphate
Carbonyl phosphate + ornithine ->?
Citrulline
Citrulline + aspartate ->?
Argenine succinate
What are used for exercise in muscles during prolonged exercise or starvation?
Branched aas:
Leucine, isoleucine and valine
How does ammonia get from the peripheral tissues to the liver?
Most synthesise glutamine from glutamate
Glutamine then travels to the liver where glutamate is made
Glutamate undergoes transamination to form pyruvate
Pyruvate used to synthesis glucose
What is the glucose Alanine cycle?
Glucose metabolised to pyruvate in tissue
Pyruvate then used in transamination to form alanine which is transported back to the liver
What are ketogenic amino acids?
Isoleucine, leucine, Tryptophan, phenylalanine, tyrosine, lysine
What are ketogenic amino acids broken down to form?
Acetyl CoA
What are glutagenic amino acids?
Alanine, cysteine, glycine, serine, threonine, tryptophan, valine
What happens to glutagenic amino acids?
Broken down and fed into TCA cycle and at the point of phosphoenolpyruvate used to make glucose
