Amino Acid and Protein Metabolism Flashcards
Explain the importance of dietary protein?
- only some amino acids can be synthesised in the body, other need to be ingested
- amino acids are required to make proteins and for neurotransmitters, nucleotides, creatine
- they act as a source of blood glucose in fasting and starvation
What is the amino acid pool?
All the amino acids in the extracellular fluid.
They are free amino acids and they can mix and exchange with other free amino acids distributed throughout the body.
What is the average turnover of amino acids in the body per day?
300g-400g
Most proteins have a half life of a few days. Which protein is an exception?
Collagen
Can we store protein in the body?
What happens to surplus amino acids?
No storage form of protein
Surplus is rapidly catabolised and the nitrogen excreted as urea
How many amino acids do we rely on the diet to give us?
Half (10)
What are 3 essential amino acids we need to make?
- alanine
- aspartate
- glutamate
What is a healthy nitrogen balance in an adult?
Total nitrogen intake should be equal to the total nitrogen excretion.
Give details on positive nitrogen balance
N intake > N excretion Protein synthesis exceeds the rate of breakdown During normal growth in children In convalescence after serious illness After immobilisation after an accident In pregnancy
Give details on negative nitrogen balance
N intake < N excretion In starvation During serious illness In late stages of some cancers In injury and trauma If not corrected and becomes prolonged, there will be irreversible loss of essential body tissue and will ultimately lead to death
What happens in the degradation of most cellular proteins?
Foreign proteins?
cellular = recognised as old and removed by ubiqutin breakdown system giving a mixture of the 20 amino acids
Foreign exogenous protein - taken into vesicles by endocytosis or autophagocytosis, the vesicle fuses with lysosomes and proteolytic enzymes degrade proteins into amino acids
What is formed from amino acid degradation?
Pyruvate
What happens in oxidative deamination?
Water and a coenzyme is added to an amino acid and this forms a keto acid, ammonia and the coenzyme.
When transamination occurs, an amino acid is added to 2-oxaglutarate to form what?
an oxo acid and glutamate
What do all aminotransferases contain?
A tightly bound prosthetic group which is derived from vitamin B6 and it acts as a carrier of the amino group
