Nitrogen Metabolism

Front 1

list all the essential amino acids

Back 1

valine, threonine, leucine, isoleucine, metheonine

histidine, arginine

lysine, tryptophan, phenylalanine, tyrosine

Front 2

what is the nitrogen enzyme glutamate dehydrogenase responsible for

Back 2

detoxification - removing ammonia from the circulation and providing it for the urea cycle

NH4+ + alpha-ketoglutarate > glutamate + water

driven by the reduction of NADH + H+ > NAD+

Front 3

what is the nitrogen enzyme glutamine synthetase responsible for

Back 3

detoxifies ammonia esp. in the CNS for transport to the liver

Glutamate + NH4+ + ATP > Glutamine + ADP + Pi

Front 4

what is the nitrogen enzyme glutaminase responsible for

Back 4

in the liver it releases ammonia for the urea cycle substrate

Glutamine > Glutamate + NH4+

Front 5

what are the nitrogen enzymes transaminases responsible for

Back 5

eg alanine transaminase (ALT)

Alanine + alpha-ketoglutarate > pyruvate + glutamate

Front 6

how are amino acids synthesised

Back 6

AAs are produced by transaminase reactions when amino groups are transferred to keto acids (carbon skeleton)

Front 7

how are amino acids broken down

Back 7

1st of all the amino group is removed and transferred to alpha-ketoglutarate by transaminases

and is then directed towards the urea cycle

the carbon skeleton enters intermediary metabolism where it can be broken down to form energy

Front 8

what are the effects of ammonia toxicity

Back 8

- neurological disease due to neurotransmission problems caused by the increased pH

- decline in CNS function due to a decrease in ATP production from the TCA cycle

Front 9

ammonia is a by-product of neurotransmission so how is it removed from the brain

Back 9

it combines with glutarate to form glutamine which is then able to pass through the blood-brain barrier to the plasma

Front 10

ammonia is produced in muscles post exercise, how is it removed

Back 10

combines with alpha-ketoglutamate to form glutamate

glutamate then combines with pyruvate to form alpha-ketoglutarate and alanine which is then able to pass through the plasma membrane to the blood and be absorbed by the liver

Front 11

how is ammonia removed from the liver

Back 11

by the urea cycle

Front 12

how do ammonotelic animals like fish remove ammonia from their bodies

Back 12

release free ammonia into the environment

Front 13

how do uricotelic animals like birds remove ammonia from their bodies

Back 13

they produce uric acid which has a low solubility and crystals form so there is no need for water of the solution

Front 14

how do ureotelic animals remove ammonia from their bodies

Back 14

they produce urea which is highly soluble and water is los during excretion

Front 15

what is it that makes urea highly soluble

Back 15

the amino groups are not protonated

Front 16

what substrates are required for the urea cycle

Back 16

ammonia

formate (HCOO-)

aspartate

energy

Front 17

what molecule is the urea cycle dependant on and how is synthesis of this stimulated

Back 17

N-acetyl glutamate

stimulated by arginine and glutamate both of which are elevated when free amino acids elevated