Which statement best defines mechanical digestion?

Which statement best defines mechanical digestion?

• A. Physical breakdown of food
• B. Chemical breakdown of food by enzymes
• C. Absorption of nutrients through the intestinal lining
• D. Storage of chyme in the stomach

Answer: (A)

Mechanical digestion refers to the physical processes that break food into smaller pieces without changing its chemical composition. This includes actions like chewing and the stomach’s churning that fragment food and mix it with saliva or gastric contents, increasing the surface area for enzymes to act later. This is distinct from chemical digestion, where enzymes break chemical bonds to form smaller molecules. The statement describing physical breakdown of food best captures what mechanical digestion does. The other options describe chemical digestion (enzymes breaking down food), absorption (nutrients crossing the intestinal lining), or storage of chyme (a function of the stomach that isn’t digestion).

Mechanical digestion refers to the physical processes that break food into smaller pieces without changing its chemical composition. This includes actions like chewing and the stomach’s churning that fragment food and mix it with saliva or gastric contents, increasing the surface area for enzymes to act later. This is distinct from chemical digestion, where enzymes break chemical bonds to form smaller molecules. The statement describing physical breakdown of food best captures what mechanical digestion does. The other options describe chemical digestion (enzymes breaking down food), absorption (nutrients crossing the intestinal lining), or storage of chyme (a function of the stomach that isn’t digestion).