3.5 gluconeogenesis, nitrogen metabolism and amino acid balance Flashcards
what are the 4 enzymes involved in gluconeogenesis of pyruvate into blood glucose
pyruvate carboxylase
PEP carboxylase
fructose 1,6 bisphosphatase
glucose 6 phosphatase
what does pyruvate carboxylase do
Adding carbon to pyruvate to form oxaloacetate
what does PEP carboxylase do
Converting oxaloacetate to PEP
what does fructose 1,6 bisphosphatase do
converting fructose 1,6 bisphosphate into fructose 6 phosphate
what does glucose 6 phosphatase do
converting glucose - 6 phosphate into blood glucose
define gluconeogenesis
making glucose from non carbohydrate metabolic intermediates
what are some non carbohydrate metabolic intermediates during fasting
amino acids, glycerol
what are some non carbohydrate metabolic intermediates during intense exercise
lactate
what are some non carbohydrate metabolic intermediates when converting absorbed nutrients into glucose
○ Converting absorbed nutrients into glucose
Propionate (ruminants)
An animal is in nitrogen balance when:
N intake = N excretion
An animal is in positive nitrogen balance when and why
- An animal is in positive nitrogen balance when:
N intake > N excretion (e.g. Growth and pregnancy)
An animal is in negative nitrogen balance when and why
- An animal is in negative nitrogen balance when:
N intake < N excretion (e.g. starvation - not enough proteins)
source of amino acid in the pool
- endogenous proteins
- dietary proteins
how is the amino acid used
NH3 is removed to form alpha-keto acid which is then used for synthesis (anabolic) or energy production (catabolic)
what else does amin acids form
- It also forms non-protein nitrogenous compounds
e.g. neurotransmitters and nucleotides
how is ammonia excreted in ammoniotelic, uricotelic, and ureotelic animals
Ammoniotelic organisms (e.g., fish) excrete ammonia directly.
Uricotelic organisms (e.g., birds, reptiles) excrete uric acid, which contains four nitrogen atoms.
Ureotelic organisms (e.g., mammals) convert ammonia to urea, which is excreted in urine.
what happens in transamination
The amino group and the carboxyl group switches
amino acid and alpha keto-glutarate is converted into glutamate and alpha-keto acid
how do glutamate convert into glutamine and why
○ Glutamate is converted into glutamine by adding NH4+ (amino acid - solid form - easier transport)
it needs to be transported to the liver
what happens to glutamine when it is transported to the liver
In the liver, glutamine is converted back into glutamate by a different enzyme reaction.
The NH4+ released is used for urea synthesis
what happens to ammonia when it is released in the liver
it combines with CO2 and enters the urea cycle
what happens when levels of ammonia in blood rises
ammonia intoxication
what will the build up of ammonia causes (2)
- The build up of ammonia will reverse glutamate dehydrogenase reaction
- this uses up α-ketoglutarate (intermediate in citric acid cycle)
2, It also promotes conversion of glutamate, neurotransmitter, to glutamine
clinical signs of ammonia intoxication (4)
- intolerance to high protein food
- vomiting
- coma
- death
causes of ammonia intoxification
- genetic defect
- liver damage or diseases
treatments to improve ammonia intoxification
- low protein diet food
- eat small amount of protein at regular intervals
