[FMS] NAM - amino acid metabolism Flashcards
(38 cards)
what is the average adult protein turnover?
What are the body’s protein requirements?
turnover 300-400g/day
recommendation: 50 – 70 g protein per day
what is the half-life of proteins?
most proteins have half-lives of several days
structural proteins have half-lives of years
Hormones & digestive enzymes are degraded very rapidly, with half-lives of minutes.
what is the recommendation of protein daily?
50-70g
how many essential amino acids are there?
20
which 10 amino acids can the body synthesize on its own
remember “private tim hall”
P = phenylalanine
V = valine
T = threonine
T = tryptophan
I = isoleucine
M = methionine
H = histidine
A = arginine
L = leucine
L = lysine
what is nitrogen balance?
N (intake) = N (excretion)
nitrogen excretions are in what form?
- urea
- uric acid
- creatinine
- NH4+
what is a positive nitrogen balance?
N (intake) > N (excretion)
intake more than excretion
when does a positive nitrogen balance occur
- normal children growth
- convalescence after serious illness
- in pregnancy
- after immobilisation after accident
what is a negative nitrogen balance?
N (intake) < N (excretion)
excretion more than intake
when does a negative nitrogen balance occur
- in starvation
- during serious illness
- late cancer stages - cachexia
- injury and trauma
^ If not corrected and becomes prolonged, there will be irreversible loss of essential body tissue
will ultimately lead to death.
what is the pathway of protein degradation for cellular proteins
- If they are recognised as ‘old’ or damaged they are removed by the ubiquitin breakdown system
- They are a mixture of the 20 amino acids
what is the pathway of protein degradation for exogenous proteins
- ‘old’ or damaged sub cellular organelles are taken into vesicles by endocytosis, or autophagocytosis. The vesicle fuses with lysosomes and proteolytic enzymes degrade proteins into amino acids
- Starvation and hormones (e.g. cortisol increase) rates of protein breakdown in muscle
what are amino acids degraded into? ie what are amino acids made of?
It is an oxo (keto) acid with an amine group.
what are the two processes of aa degradation?
oxidative deamination and transamination
What is transamination?
transfer of the amino group of an amino acid onto a keto acid to produce the amino acid of that keto acid and the keto acid of that amino acid.
what does transmination need?
- amino acid
- keto acid
- aminotransferase with pyridoxal phosphate
outline what happens in deamination
outline what happens in transamination
remember: TRANSamination = TRANSfer
what is the fate of oxo-acids in starvation?
carbon skeletons of 13 amino acids converted back to glucsoe by liver, these are classified as ‘glucogenic’.
what are ketogenic amino acids
Leucine and lysine
^ These can only be degraded to acetyl CoA, not pyruvate
what are the 5 glucogenic and ketogenic amino acids?
phenylalanine, tyrosine, tryptophan, isoleucine, threonine
REMEMBER: PITTT
what is the difference between glucogenic and ketogenic amino acids and its ability to be converted to glucose?
glucogenic = can be converted back to glucose by liver
ketogenic = cant be converted back to glucose, can only be degraded to acetyl coA, leucine, lysine
What are the important amino acids in the inter-organ transport of nitrogen?
- Alanine - can be deaminated into pyruvate but not directly
- Glutamate - can be deaminated into pyruvate directly
- Glutamine - can be deaminated into pyruvate but not directly, goes to glutamate to alpha-ketaglutarate.
- Aspartate - can be deaminated into pyruvate but not directly, goes to oxaloacetate.
