Q53 / 200 · MHT CET - Medical 2026 (24 April Shift 2) · Biology
Which of the following is NOT bacterial activity in the human alimentary canal?
- AFermentation of carbohydrates and production of methane gas.
- BDigestion of protein and production of substances like indole, skatole etc.
- CSynthesis of Vitamin B
- Correct answerDSynthesis of Vitamin D
Solution
Bacteria in the human alimentary canal (specifically in the large intestine) perform several important functions.
They ferment undigested carbohydrates, producing gases such as methane, hydrogen, and carbon dioxide.
They also break down undigested proteins, producing substances like indole, skatole, and hydrogen sulfide, which contribute to the characteristic odor of feces.
Furthermore, gut bacteria synthesize essential vitamins, including Vitamin K and several B vitamins (such as B12, thiamine, and riboflavin).
However, Vitamin D is not synthesized by gut bacteria. It is synthesized in the skin from 7-dehydrocholesterol upon exposure to ultraviolet (UV) radiation from sunlight, and subsequently activated in the liver and kidneys.
Therefore, the synthesis of Vitamin D is not a bacterial activity in the human alimentary canal.
Answer: Synthesis of Vitamin D
They ferment undigested carbohydrates, producing gases such as methane, hydrogen, and carbon dioxide.
They also break down undigested proteins, producing substances like indole, skatole, and hydrogen sulfide, which contribute to the characteristic odor of feces.
Furthermore, gut bacteria synthesize essential vitamins, including Vitamin K and several B vitamins (such as B12, thiamine, and riboflavin).
However, Vitamin D is not synthesized by gut bacteria. It is synthesized in the skin from 7-dehydrocholesterol upon exposure to ultraviolet (UV) radiation from sunlight, and subsequently activated in the liver and kidneys.
Therefore, the synthesis of Vitamin D is not a bacterial activity in the human alimentary canal.
Answer: Synthesis of Vitamin D
Hence, the correct answer is option: 'D'.