Which of the following deaminates excess amino acids?

Step 1: Analyze the question The question asks which organ carries out deamination, which is the removal of the amino group (-NH₂) from excess amino acids.

Step 2: Explain the concept The body cannot store excess amino acids. Instead, they are processed as follows:

• The amino group is removed (deamination) and converted to ammonia.
• Ammonia is converted to urea through the ornithine (urea) cycle.
• The remaining carbon part (keto acid) is used for energy or converted to glucose or fat.
• Urea travels in the blood to the kidneys and is excreted in urine.

All of the deamination and urea formation takes place in the liver.

Step 3: Evaluate the options

• A. Duodenum: Part of the small intestine. It receives bile and pancreatic juice and carries out digestion, not deamination.
• B. Ileum: Absorbs digested food, including amino acids. It does not deaminate them.
• C. Kidney: Filters urea from the blood and excretes it. This is a common trap, because the kidney removes the urea but does not make it.
• D. Liver: Deaminates excess amino acids and makes urea. This is correct.
• E. Pancreas: Secretes digestive enzymes such as trypsin, amylase and lipase, and hormones such as insulin and glucagon. It plays no role in deamination.

Step 4: Answer The correct answer is D. Liver.

Tip: Remember "Liver makes, Kidney takes." The liver makes urea by deamination, and the kidney takes the urea out of the blood for excretion. Other key liver functions to remember are deamination, glycogen storage, detoxification, bile production and breakdown of old red blood cells.