Deamination of amino acids in the liver produces

Analyze the question: Deamination is the removal of the amino group (-NH₂) from an amino acid. The question asks what product the liver makes from this process.

Explain the concept: Excess amino acids cannot be stored in the body. The liver processes them in two stages:

1. Deamination: the amino group is removed from the amino acid. This leaves a carbon-containing part (a keto acid) and ammonia (NH₃).
2. Urea formation: ammonia is toxic, so the liver quickly converts it to urea through the ornithine (urea) cycle. Urea is carried in the blood to the kidneys and excreted in urine.

The leftover keto acid can be used for energy or converted to carbohydrate or fat.

Step-by-step solution:

• Amino acid → (deamination) → keto acid + ammonia
• Ammonia + CO₂ → (ornithine cycle) → urea

Checking the options:

• A. Blood sugar: glucose comes mainly from carbohydrate breakdown or glycogen. It is not the direct product of deamination.
• B. Glycogen: this is the storage form of carbohydrate, made from glucose, not the product of removing an amino group.
• C. Bile: this is made from the breakdown of haemoglobin and from cholesterol. It has nothing to do with amino acids.
• D. Urea: this is the nitrogenous waste made from the ammonia released in deamination. Correct.

Answer: D. urea

Exam tip: Remember "De-AMIN-ation → AMMONIA → UREA." Whenever you see nitrogen or an amino group being removed in the liver, think urea. Also remember that bile is a digestive fluid for fats and is not a nitrogenous waste.