Session 1- protein and aa metabolism Flashcards
What effect do these hormones have on protein synthesis?
- Insulin
- Growth hormone
- Cortisol
How does cortisol exert its effect?
Insulin and growth hormone promote uptake of amino acids and protein synthesis
Cortisol promotes proteolysis in muscle by activating aminotransferases in the liver
Is excess protein stored?
No, the amino acids are converted to metabolites or excreted
What is the first step in amino acid breakdown?
Removal of the amino group by transamination/ deamination
Amino acid catabolism; What happens to the amino group?
What is the remaining structure called?
If not transferred to another aa, it is converted to urea and excreted via the urine
Urea; (CO(NH2)2)
C-skeleton of the amino acid
What are ketogenic and glucogenic amino acids?
The C-skeletons of ketogenic amino acids produce acetyl CoA which can make ketone bodies
C-skeletons of glucogenic amino acids produce intermediates in gluconeogenesis. E.g. pyruvate
Name two ketogenic amino acids
Name amino acids which are both ketogenic and glucogenic
Lysine & leucine
Tryptophan Tyrosine Isoleucine Phenylalanine Threonine
Metabolism of glucose, fatty acids, amino acids and ketone bodies all produce which molecule?
Acetyl CoA
enters the TCA cycle
How many kg of nitrogen is there in the body?
Most of the nitrogen in the body is found where?
Approx. 2kg
Mostly proteins (90%) then DNA & RNA
Average half life of a protein?
Total protein turnover per day in an adult?
80 days
300-400 g per day
What is a positive nitrogen balance?
When does it occur?
Taking in more protein than you excrete
Periods of active growth, pregnancy and tissue repair
What is a negative nitrogen balance?
When does it occur?
Taking in less nitrogen than you excrete
Starvation, malnutrition, trauma
How does nitrogen enter and leave the body?
Enters mostly in protein
Leaves via - urea (85%) - creatinine - ammonia - uric acid some direct loss of protein via hair, skin, nails
How to remember the 10 essential amino acids?
PVT TIM HALL
Phenylalanine valine threonine tryptophan isoleucine methionine histidine arginine (conditional) leucine lysine
Name three amino acids which are conditionally essential
Explain when they become essential
Tyrosine - only if phenylalanine is low (its precursor)
Arginine - only during periods of active growth bc the body can produce small amounts
Cysteine - only if methionine (its precursor) is low
Which amino acid is the precursor for Tyrosine?
Phenylalanine
Which amino acid is the precursor for Cysteine?
Methionine
Normal fasting concentration of amino acids in the blood?
3mmol/L
Which 4 non-essential amino acids make up 50% of the free pool?
glutatmine, alanine, proline, glycine
Why do you need to keep taking in amino acids if most are recycled?
To replace those which are lost
Where do the carbon and nitrogen atoms come from to make new amino acids?
- carbon from intermediates of glycolysis, the pentose phosphate pathway and the Krebs Cycle
- amino group from transamination or ammonia
What happens to excess amino acids?
Converted to intermediates of carbohydrate and lipid metabolism OR
oxidised for energy
Which two signalling molecules are made from amino acids?
nitric oxide (from L-arginine)
Hydrogen sulphide (from L-cysteine)
These amino acids are used to make what nitrogenous compounds?
- Trytophan
- Histidine
- Tyrosine
- Glycine
- seratonin, 5-HT
- histamine
- thyroid hormones, melanin, catecholamines
- purines, porphyrins, creatine, glutathione
Where does most amino acid catabolism occur?
How does use of acetyl CoA change in starvation?
liver
Usually oxidised to CO2 and water but in starvation/ diabetes, it’s converted to ketone bodies and glucose
