Describe transamination and oxidative deamination of amino acids.

1. 1 · Open in two lines. Amino acids lose their nitrogen in two linked steps. Transamination collects the amino group on glutamate; oxidative deamination then frees it as ammonia.
2. 2 · Draw transdeamination. [Diagram: amino acid + α-ketoglutarate → keto acid + glutamate (transaminase, PLP); glutamate → α-ketoglutarate + NH₃ (GDH, NAD⁺) → urea cycle]
3. 3 · Explain transamination.
   • Definition; PLP as coenzyme (two half-reactions, PLP ⇌ PMP).
   • Examples: the ALT and AST reactions.
   • Reversible; all amino acids except lysine and threonine take part.
4. 4 · Explain oxidative deamination.
   • Glutamate dehydrogenase in liver mitochondria, using NAD⁺ or NADP⁺.
   • Regulation: ATP and GTP inhibit; ADP and GDP activate.
   • Minor route: L- and D-amino acid oxidases.
5. 5 · Significance. Funnels amino nitrogen to glutamate and then to urea; makes non-essential amino acids; links amino acid and carbohydrate metabolism; ALT and AST are liver markers.
6. 6 · Nutrition link. Vitamin B6 (PLP) runs every transaminase; niacin supplies NAD⁺ for GDH.
7. 7 · Close in one line. Sum up: transamination collects nitrogen, deamination frees it for the urea cycle.

Scoring tip: Word equations with the enzyme written over each arrow are enough. Examiners look for PLP and glutamate dehydrogenase by name.