Protein Breakdown + Urea Formation Flashcards
Metabolism of amino acids
Amino acids are either used or broken down but not stored
What are 2 parts of amino acids?
Carbon skeleton
Nitrogen
What is carbon skeleton of amino acid used for?
Energy metabolism
Biosynthetic pathway
The removal of nitrogen
Nitrogen is toxic so has to removed safely
In mammals, nitrogen is converted to non-toxic neutral compound urea + excreted in urine
What are 3 steps in which nitrogen from amino acids are transferred to urea?
Transamination
Formation of ammonia
Formation of urea
What enzymes are involved in transamination?
What do they do?
Amino transferase
2 most important are alanine transferase and aspartame transferase
They transfer amino group from an amino acid to a-keto acid
What are 3 a-keto acids?
a-ketoglutarate, pyruvate + oxaloacetate
What occurs in formation of ammonia?
Ammonia formed is substrate for urea cycle
Glutamate can form ammonia directly by action of glutamate dehydrogenase
Reaction is fully reversible and can use either NAD or NADP
Elimination of free ammonia
Free ammonia generated in tissue combines with glutamate to give glutamine
Enzyme involved is glutamine synthase
What is urea cycle?
Means of excreting nitrogen
Enzyme present in liver but not muscle
Take place in mitochondria + cytoplasm
Substrates are bicarbonate, aspartate, ammonium ions (released from glutamine or glutamate)
What occurs in formation of urea?
Uses 2 amino groups
Bicarbonate= breakdown of carbon skeleton
Ammonium ions from glutamate
Aspartate comes from transamination
What are 2 types of amino acids?
Glucogenic
Ketogenic
Positive nitrogen balance
Taking in more nitrogen than excreting Enhanced by anabolic steroids Exercise Process growth Pregnancy
Negative nitrogen balance
Not taking in sufficient
Breaking down more than you are taking in
Protein deficiency
Pathological process
