The bacteria in the large intestine of man synthesizes

Analyze the question: It asks what the gut bacteria (intestinal flora) in the human large intestine manufacture, or synthesize.

Concept: The large intestine hosts a large community of symbiotic bacteria, such as Escherichia coli. They feed on undigested food and in return produce useful substances:

• Vitamin K (needed for blood clotting)
• Some B vitamins, such as B12, biotin, and folate
• Some amino acids, which can be produced by bacterial metabolism, and short-chain fatty acids

Evaluate the options:

• A. Vitamins and minerals: Minerals are elements, so bacteria cannot synthesize them. Wrong.
• B. Vitamins and glucose: Glucose is made by photosynthesis in plants, not by gut bacteria. Wrong.
• C. Amino acids and vitamins: Both are products of gut bacterial metabolism. This is the best fit.
• D. Amino acids and minerals: Minerals cannot be synthesized. Wrong.

Tip: Minerals are elements, so nothing living can "make" them. Whenever you see "minerals" in a "synthesizes" question, you can eliminate that option. Also remember "gut bacteria → Vitamin K and B vitamins."