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Ammonia + The Urea Cycle - Coggle Diagram
Ammonia + The Urea Cycle
Disposal of nitrogen
Liver + kidney
Amino acid degradation produces ammonia + carbon skeleton
Toxic
Occurs in liver
NH\(_3\) detoxified in urea cycle by liver
Carbon skeleton
Gluconeogenesis
TCA cycle
Urea is major end product of nitrogen metabolism
Urea transported to kidneys
Excreted in urine
Kidneys also excrete ammonia as NH\(_4^+\)
Acid base regulation
[ammonia excreted] dependent on [protons excreted]
Non-protein nitrogenous substances
Uric acid 6%
Creatinine 5%
Ammonia 3%
Urea 86%
Nitrogen transport
Ammonia is neurotoxic
Non-toxic form needed for transport
Ammonia transported from peripheral tissues in 2 forms
Glutamine
Ammonia incorporated to glutamate
\(\alpha\)-ketoglutarate + \(NH_4^+\)
Glutamate + \(NH_4^+\)
Glutamine
Transported to liver
Glutamine
Loses \(NH_4^+\)
Glutamate
3 more items...
Catalysed by glutaminase
Via bloodstream
ATP
ADP + P\(_i\)
Catalysed by glutamine synthetase
NADPH
NADP\(^+\)
Catalysed by glutamate dehydrogenase
Alanine
Transport form from muscles
Main ammonia transporter produced in muscle
High levels of pyruvate produced in muscle
\(\alpha\)-ketoglutarate + \(NH_4^+\)
Glutamate + pyruvate
Alanine
Transported to liver
Via bloodstream
Alanine breakdown
Carbon skeleton
1 more item...
Nitrogen
1 more item...
Amino acid
\(\alpha\)-ketoacid
Urea cycle
Converts ammonia to urea
Mitochondrial + cytosolic
2 nitrogen atoms
1 from ammonia
1 from aspartate
Formation of ammonia in liver
Glutamate plays essential role
Amino group from amino acid transferred to \(\alpha\)-ketoglutarate to form glutamate
Oxidative deamination by GDH forms free ammonia
Glutamate also produced in reverse reaction to remove free ammonia
Also by glutaminase reaction to form glutamine
Overall reaction
Ammonia + aspartate
Urea + fumarate
3ATP
2ADP + 2P\(_i\) + AMP + PP\(_i\)
Reactions
5 enzymatic reactions
3 cytosolic
2 mitochondrial
First reaction
In mitochrondion
Condensation + activation of ammonia + bicarbonate
Catalysed by carbamoyl phosphate synthetase I
Hydrolysis of 2ATP
Rate limiting step in cycle