Flashcards in MEH - Protein/Amino Acid Metabolism Deck (50)
Give some examples of nitrogen containing compounds in the human body
- amino acids
- some hormones
What is creatinine?
A breakdown product of creatine and creatine phosphate in the muscle
How is creatinine excreted?
Filtered via kidneys into urine. For men, 14-26 mg/kg per day. For women, 11-20 mg/kg per day
What can creatinine be used to measure?
Creatinine urine excretion over 24h is proportional to muscle mass, so it can be used to estimate it. Also often used as indicator of renal functions (raised when nephrons are damaged)
What does it indicate if a person has a 'positive nitrogen balance'?
Intake is larger than output, so there is an increase in total body protein. Person may be growing, pregnant or recovering from malnutrition
What does a negative nitrogen balance indicate?
Intake is lower than output, so there is a net loss of body protein. Causes include trauma, infection or malnutrition
What does it mean if the body is at nitrogen equilibrium?
No change in total body protein - normal state in adult
What do glucogenic amino acids undergo in the body?
What do ketogenic amino acids undergo in the body?
Give an example of a glucogenic amino acid
Alanine, glycine, cysteine, serine, arginine, proline, histidine, glutamine, glutamate, methionine, valine, aspartate, asparagine,
Give an example of ketogenic amino acids
Give some examples of amino acids that are both glucogenic and ketogenic
Tryptophan, tyrosine, phenylalanine, threonine, isoleucine
What is the effect of insulin and growth hormone on protein synthesis/degradation?
- increases protein synthesis
- decreased protein degradation
What is the effect of glucocorticoids on protein synthesis?
- protein synthesis decreases
- protein degradation increases
Why is it important for a vegetarian diet to contain proteins from a wide variety of plant sources?
Proteins of plant origin are generally considered lower quality as most are deficient in one or more essential amino acids
What are the nine essential amino acids? (Mnemonic - if learned this huge list may prove truly valuable)
Isoleucine, lysine, threonine, histidine, leucine, methionine, phenylalanine, tryptophan, valine
Where does the body obtain the carbon atoms it requires for non-essential amino acid synthesis?
- intermediates of glycolysis
- pentose phosphate pathway
- Krebs cycle
Where does the body obtain the amino group for non-essential amino acid synthesis?
It is provided by other amino acids by the process of transamination or from ammonia
What is tyrosine used to synthesise?
Catecholamines, melanin, thyroid hormones
What is cysteine used to synthesise?
Hydrogen sulphide, glutathione
What is tryptophan used to synthesise?
Nicotinamide, serotonin, melatonin
What is histidine used to synthesise?
What is glutamate used to synthesise?
What is glycine used to synthesise?
Purines, glutathione, haem, creatine
What is arginine used to synthesise?
What is serine used to synthesise?
What is transamination?
Swapping the amine group of an amino acid with the oxygen of a keto acid
What are the two main aminotransferase enzymes?
Alanine aminotransferase (ALT - converts alanine to glutamate)
Aspartate aminotransferase (AST - converts glutamate to aspartate)
Give some examples of conditions that may cause high plasma ALT and AST levels
- viral hepatitis
- autoimmune liver diseases
- toxic injury