Protein And Amino Acid Metabolism Flashcards
What is creatinine?
A breakdown product of creatine and creatine phosphate in muscle. It is filtered via kidneys into urine and creatine urine excretion over 24h is proportional to muscle mass.
What is positive N balance?
When intake>output, increase in total body protein. Normal state in growth and pregnancy or in adult recovering form malnutrition.
What is negative N balance?
Intake<output, net loss of body protein, never normal. Causes include trauma, infection or malnutrition.
Describe Cushing’s syndrome.
Excessive breakdown of protein can occur, this weakens the skin structure leading to striae formation.
What are the 9 essential amino acids
Isoleucine, leucine, tryptophan, threonine, methionine, valine, phenylalanine, lysine, histidine
What does ALT do?
Catalase interconversion of alanine and a-ketoglutarate to pyruvate and glutamate.
What does AST do?
Catalyses interconversion of aspartate and a-ketoglutarate to oxaloacetate and glutamate.
Describe deamination
Liberates amino group as free ammonia and mainly occurs in liver and kidney. Ammonia is very toxic and needs to be removed, ultimately its converted to urea or excreted directly in urine.
Give an example of a glucogenic and ketogenic amino acid
Glucogenic: Alanine. Ketogenic: Lysine. Both: Threonine
Describe glutamine transport
Ammonia combined with glutamate to form glutamine. This is transported in blood to liver or kidneys, cleaved by glutaminase to reform glutamate and ammonia. Ammonia fed into urea cycle in liver and excreted directly in urine in the kidney.
Describe PKU
A deficiency in phenylalanine hydroxylase, causes an accumulation of phenylalanine in tissue, plasma and urine. Phenylketones in urine give a musty smell. Treatment: low phenylalanine diet, avoid artificial sweeteners and high protein foods.
Describe homocystinurias
A problem breaking down methionine, excess homocystine excreted in urine. Treatment: low methionine diet, avoid milk, meat, fish, cheese, eggs and nuts.
