Protein & Amino Acid Metabolism Flashcards
How is Creatinine formed
How is muscle mass related to creatinine urine excretion
What are 2 uses of measuring creatinine in urine
- Breakdown of Creatine and Creatine Phosphate
- Proportional
- Estimating muscle mass
- Indicates Renal function (Raised in plasma, low in urine when nephrons damaged)
What is Nitrogen Balance
When the amount of Nitrogen into the body= The amount of nitrogen leaving the body
Compare Positive and Negative nitrogen balance
When do they occur?
Positive: Intake>output
Growth/ Pregnancy/ Recovering from malnutrition
Negative: Intake
What is Protein Turnover
Compare Glucogenic and Ketogenic amino acids
Give one example of each
Give one example of an amino acid that is both
Continuous breakdown and resynthesis of proteins
Glucogenic: Used to make glucose/ glycogen (Cysteine/ Glycine)
Ketogenic: Used to make fatty acids/ ketone bodies (Lysine/ Leucine)
Both: Tyrosine/ Isoleucine
How do Insulin and Growth Hormone affect;
Protein synthesis
protein degradation
How do glucocorticoids affect these
Insulin, Growth Hormone:
- Increase protein synthesis
- Decrease protein degradation
Glucocorticoids:
- Decrease protein synthesis
- Increase Protein degradation
What is Cushing’s Syndrome?
How does it form Striae (Stretch marks)
Excess cortisol
Excessive protein breakdown, skin structure weakened-> Striae
For non-essential amino acid synthesis, where do;
- carbon atoms come from
- Amino groups come from
- Glycolysis intermediates/ Pentose Phosphate Pathway/ Krebs cycle
- Transamination OR from Ammonia
In what 2 ways can N be removed from amino acids
Transamination
Deamination
How does Transamination work?
What enzymes use what substances to change amino group
What is the exception, what substance does this use
All aminotransferase enzymes require a cofactor that is a derivative of what?
Aminotransferase enzymes use Alpha-Ketoglutarate to change amino group to Glutamate
Exception: Aspartate Aminotransferase uses Oxaloacetate to change amino group to Aspartate
Derivative of Vitamiin B6
Plasma levels of WHICH 2 Aminotransferase enzymes are measured to to test WHAT?
What do these enzymes do?
Name 3 conditions where these are in high levels
ALT: Alanine Aminotransferase- Alanine to Glutamate
AST: Aspartate Aminotransferase- Glutamate to Aspartate
Measured to test liver function
Viral Hepatitis
Toxic Injury
Autoimmune Liver Diseases
How does Deamination work?
Where does it occur mainly?
What structures are formed
Liberates amino group as free NH3
Mainly in Liver and Kidney
Keto Acids
What happens to NH3 at Physiolgical pH
How is it excreted?
Ammonia converted to Ammonium ions
Converted to Urea in Liver
Directly excreted in Urine in Kidney
How many enzymes are involved in the Urea Cycle?
How does a high/ low protein diet affect enzyme levels
How is the cycle controlled?
5
High protein diet induces enzyme levels
Low protein diet/ starvation represses levels
Inducible, but not regulated
How do mutations affect urea cycle enzymes
What 2 things does a urea cycle defect lead to?
Cause partial function loss
- Hyperammonaemia
- Accumulation/ excretion of urea cycle intermediates
Name 6 symptoms of Urea Cycle Defects
How are they managed in 2 ways?
Vomiting Lethargy Irritability Mental Retardation Seizures Coma
Low protein diet
replace amino acids in diet with keto acids
