Which statement best describes the breakdown of food in the digestive system?

• A. Food passes through the digestive tract unchanged and is absorbed directly.
• B. Food is broken down both mechanically and chemically to allow nutrient absorption.
• C. Food is broken down chemically only in the stomach by hydrochloric acid.
• D. Food is only broken down mechanically by chewing in the mouth.

Answer: (B)

Verified step by step guidance

1. Understand the purpose of the digestive system: The digestive system is responsible for breaking down food into smaller components that can be absorbed and used by the body. This involves both mechanical and chemical processes.
2. Clarify mechanical digestion: Mechanical digestion refers to the physical breakdown of food into smaller pieces, such as chewing in the mouth and the churning of food in the stomach. This increases the surface area for enzymes to act on during chemical digestion.
3. Clarify chemical digestion: Chemical digestion involves the breakdown of food molecules into their chemical building blocks (e.g., proteins into amino acids, carbohydrates into simple sugars) through enzymatic reactions. This occurs in various parts of the digestive system, including the mouth, stomach, and small intestine.
4. Evaluate the incorrect statements: The statement 'Food passes through the digestive tract unchanged and is absorbed directly' is incorrect because food must be broken down before absorption. The statement 'Food is broken down chemically only in the stomach by hydrochloric acid' is incorrect because chemical digestion occurs in multiple locations and involves enzymes, not just hydrochloric acid. The statement 'Food is only broken down mechanically by chewing in the mouth' is incorrect because digestion involves both mechanical and chemical processes.
5. Select the correct statement: The correct answer is 'Food is broken down both mechanically and chemically to allow nutrient absorption,' as this accurately describes the processes involved in digestion.