Post-absorption processing of proteins Flashcards
What does the human body do with amino acids?
Protein synthesis, glucose/glycogen, energy (ATP), fatty acids, ketone bodies, nitrogen-containing metabolites.
What can histidine be synthesised to?
Histamine
Which amino acid is used in the synthesis of serotonin?
Tryptophan
Which amino acid is used in the synthesis of dopamine, noradrenaline and adrenaline?
Tyrosine
For what compound are both glycine and arginine required?
Creatinine
What is Kwashiorkor?
A form of severe protein–energy malnutrition characterized by edema, irritability, anorexia, ulcerating dermatoses, and an enlarged liver with fatty infiltrates.
What is the aetiology of kwashiorkor?
Extreme lack of protein causes an osmotic imbalance in the gastro-intestinal system causing ascites and fatty liver. Exchange between lymphatic system and bloodstream is stunted due to inability of the body to effectively overcome the hydrostatic pressure gradient. Proteins are responsible for creating the colloid osmotic pressure (COP) observed in the blood and tissue fluids. The difference in the COP of the blood and tissue is called the oncotic pressure. The oncotic pressure is in direct opposition with the hydrostatic pressure and tends to draw water back into the capillary by osmosis. However, due to the lack of proteins, no substantial pressure gradient can be established to draw fluids from the tissue back into the blood stream. This results in the pooling of fluids, causing the swelling and distention of the abdomen.
What waste metabolite is produced from energy reactions involving proteins?
Ammonia
What are the symptoms of hyperammonaemia?
Tremor, vomiting, cerebral oedema, coma and death.
What can cause hyperammonaemia?
Genetic defects, liver disease etc..
Where does disposal of ammonia mainly occur?
Liver
What are the three steps in the ammonia disposal pathway?
Transamination, deamination and urea synthesis
What is transamination?
Transfer of amino group from AA to ketoglutarate forming glutamate (in most tissues).
What is deamination?
Release of ammonia from glutamate (mainly in the liver).
How is urea synthesised?
Via the urea cycle in the liver.
How is ammonia transported safely to the liver?
As glutamate or glutamine.
What happens once glutamate/glutamine reaches the liver?
It is deaminated and ammonia released.
What other product is released in the transaminase reaction?
Keto acid
Aside from ammonia, what other products are released from the deamination reaction?
NADPH (NADP required) and alpha-ketoglutarate
What is pyridoxal phosphate the active form of?
Vit B6
Aside from transamination, what else is Vit B6 required for?
Decarboxylation reactions required for neurotransmitter synthesis, haem synthesis, some aspects of energy metabolism and lipid synthesis.
What does lack of B6 lead to?
Anaemia (lack of haem), neurological symptoms (lack of neurotransmitters), poor growth, skin lesions, poor immune response (lack of protein synthesis).
Where does the urea cycle take place?
Inside the mitochondrion and the cytosol.
What is the control step in the urea cycle?
Carbamoyl group transferred to ornithine to form citrulline (inside the mitochondria). This the entry point to the urea cycle.
