MEH - Protein and amino acid metabolism Flashcards
Name 4 important nitrogen containing compounds in the body
Proteins
Amino acids
RNA/DNA
Creatine
What is creatinine and what is it used for clinically (2)?
Breakdown of creatine and phosphocreatine in muscle.
Usually excreted at a constant rate - is proportional to muscle mass so can be used to estimate muscle mass
Also indicator of renal function (raised level on damage to nephrons)
What are the normal figures for nitrogen balance in 70Kg man? What is the amino acid pool in the body?
16g in via diet
2g out via hair skin nails
14g out via urine and faeces
16g amino acid pool
Is a negative nitrogen balance normal? What are some causes?
Never normal
Causes e.g. infection, malnutrition, trauma
What part of protein metabolism is a potential source of ammonia?
Removal of the amino group - ammonia quickly converted to urea which isn’t toxic
Ammonium ions are also toxic
Name a glucogenic, ketogenic amino acid and one that does both
1) Glucogenic - Alanine
2) Ketogenic - Lycine
3) Both - Tryptophan
When does AA mobilisation occur? How is it regulated?
During extreme starvation
Under hormonal control:
Insulin/growth hormone - decrease mobilisation and increase protein synthesis
Cortisol - increase mobilisation and decrease protein synthesis
How can Cushing’s syndrome lead to striae?
Excess cortisol
Excess protein breakdown
Weakens skin structure - striae
What are the 9 essential AAs? If Learnt This Huge List May Prove Truly Valuable
Isoleucine Lysine Threonine Histidine Leucine Methionine Phenylalanine Tryptophan Valine
Which amino acids are conditionally essential and what does this mean?
Arginine
Tyrosine
Cysteine
In pregnancy/children these may become essential so will need to be supplemented from the diet
Non-essential amino acids can be synthesised - Where does the carbon skeleton come from for this (3)? Where does the amino group come from (2)?
Can come from:
Glycolysis intermediates (C3) Pentose phosphate pathway (C4 & C5) Krebs Cycle (C4 & C5)
Amino group comes from transamination from another amino acid - or from ammonia.
What is hydrogen sulphide and what is the relevance of amino acids in relation to it?
It is a signalling molecule that requires specific amino acids in it’s synthesis
What other types of compounds require amino acids for their synthesis?
- Some neurotransmitters - GABA, 5-HT
- Hormones - e.g. thyroid
- Signalling molecules - NO
What part of the amino acid is used in oxidative metabolism and how?
The carbon skeleton
- Removal of amino group
- Carbon skeleton will then go onto make ketones or glucose to then go onto stage 3 and 4 metabolism (TCA cycle and ETC)
What is the most common amino acid formed from transamination? From what intermediate (ketoacid).
Glutamate from alpha-ketoglutarate