Amino Acid Metabolism Flashcards
What are the sources of free amino acids in the body?
Degradation of: ingested protein, biosynthesis of some (non-essential), and degradation of endogenous protein
Differentiate essential from non-essential amino acids
Essential: cannot be synthesized by the body- has to be eaten in the diet
Non-essential: amino acids that can be synthesized via other pathways. Does not have to be eaten
What are free amino acids used for?
Resynthesis of endogenous protein Precursors for the synthesis of other biomolecules Energy production (and amino group is excreted as urea in the process)
Is the biosynthesis of amino acids sufficient to allow net synthesis of protein?
No. If you don’t eat enough protein in your diet, you will eventually lose muscle mass
What are two pathways by which protein degradation occurs?
Lysosome and proteosome
What is the half life of a protein?
The range varies from minutes to days
What is the “turnover” of protein in an adult?
Adults degrade and resynthesize 2-3% (~300g) of their total body protein every day.
What happens to excess amino acids?
Excess amino acids are degraded, not stored.
What is the recommended dietary allowance for daily protein?
55g
55g of amino acids are degraded daily. What are they being used for?
Biosynthesis of purines, pyrimidines and porphyrins
Carbon skeletons: (used for energy)
What would happen if you ate a protein free diet?
You would lose muscle mass. The body requires 55g of protein per day, and thus you would break down muscle mass for an additional amino acid supply
Define nitrogen balance
Nitrogen ingested (protein) = nitrogen excreted (urea)
If you eat more protein, you pee out more urea
The degradation of amino involves what two processes? What is their role?
1) Removal of the nitrogen to form urea –> excretion for nitrogen balance
2) Degradation of the carbon skeletons –> energy production
What is the first step in the degradation of many amino acids?
transamination
Where does biosynthesis urea occur?
The liver