Nitrogen - created from Mind Map

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Why Nitrogen

Nitrogen Balance

Nitrogen Metabolism

AA Metabolism

In all living organism

3% dry human weight

Animal Waste (Urea/ ammonia/ plants that cannot fix nitrogen)

Protein content constant between 10-15%

NB = Nitrogen ingested - Nitrogen excreted

NB = 0 --> protein synthesis = Protein degradation

NB = + --> PS > PD

NB = - --> PS < PD

Physiological aspects

Protein Degradation

Digestion

Absorption

Excretion

Cannot be absorbed directly from intestine

Hydrolysed by proteases and peptidases to AA tripeptides, dipeptides.

1st MAJOR site = Stomach ---> PEPSIN

Then: - Pancreatic Ez - trypsin / chymotrypsin

then Intestinal peptidases.

AA and small peptides transported into the intestinal cells

Brush border with AA specific transports - require Na+

N2 constantly being lost

Urea - 12-20g a day

Ammonium

Uric acid

Creatine

Amount depends on metabolic state of Ureotelic-excrete urea

Protein turnover

Ubiquitin

Urea cycles

Rates of breakdown / turnover different

Some Ez = few hours /// Red blood cells - 120 days

Small Regulatory Protein. 76 AA

Found in all eukaryotic cells

Directs proteins to compartments in the cell.

Citruline transported across inner membrane by neutral AA carrier

FUMARATE - transported into mitochondrial matrix for conversion to malate

The enzyme Carbamoyl phosphate synthetase

Why?

Urea Formation

Deficiency of Urea cycle

Ammonia is toxic

Readily ionises to ammonium ion.

Liver / Excreted by kidney

Hyperammonemia

Treatment

Elevates ammonia in the blood which is toxic especially in the brain

High Ammonia levels leads to..

Drive Glutamine synthase

As a result - Glutamate dehydrogenase

Leads to Glutamate depletion

Leads to depletion of α-ketoglutarate

PLays big role in cancer

Which is an essential Krebs cycle intermediate - could impair energy to the brain.

Catalyses reversible oxidative deamination of...

Depends on the deficient Ez

Limited protein Intake = adding a-Keto acid to the diet

Liver Transplant - liver carries out urea cycle

Transamination

Deamination

Formation of urea

Conversion of AA to Ez

1st reaction - glutamate production

2nd - transfer of Amino Group - Formation of Aspartate

Aspartate used in urea synthesis

Catabolic (Break down) Pathway of: Threonine, Glycine, Serine, Cysteine and Alanine

The catabolic pathway of Lysine, Tryptophan, Phenylalanine, Tyrosine and Leucine

Phenylalanine to Tyrosin

The catabolic pathway of Arginine, Proline, Histidine, Glutamine and Glutamate

The catabolic pathway of Methionine, Isoleucine, valine.

Carbon skeletons

SUMMARY

! Important ! Form acetyl CoA

Production of ATP

"Building block of proteins"

Catalysed by Phenylalanine-4-monooxygenase

Irrevesible reaction

Production of α- ketoglutarate.

Krebs / Citric acid cycle

Forms - Succinyl - CoA

Krebs / citric cycle

Glucogenic

Ketogenic

TCA intermediates or Pyruvate

I.E Energy source

Acetyl CoA

Acetoacetyl CoA

Acetoacetate