Study Notes
Digestion involves breaking down food into smaller pieces and molecules for absorption. Mechanical digestion — the physical breakdown of food without chemical change. Example: Chewing in the mouth and churning in the stomach. Chemical digestion — the breakdown of large, insoluble molecules into small, soluble molecules. Example: Salivary amylase breaking down starch into maltose in the mouth. Tooth decay — damage to tooth structures like enamel and dentine caused by plaque acid. Example: Bacteria on teeth digest sugar, producing acid that erodes enamel. Bile — a green alkaline liquid produced by the liver that emulsifies fats and neutralizes stomach acid. Example: Bile increases the surface area for lipase to work in the small intestine. Villi — microscopic projections in the small intestine that increase surface area for absorption. Example: Villi have thin walls and a good blood supply for efficient nutrient absorption.
Exam Tips
Key Definitions to Remember
- Mechanical digestion: Physical breakdown of food without chemical change.
- Chemical digestion: Breakdown of large, insoluble molecules into small, soluble molecules.
- Bile: Alkaline liquid that emulsifies fats and neutralizes stomach acid.
Common Confusions
- Mixing up mechanical and chemical digestion.
- Confusing the roles of bile and enzymes in digestion.
Typical Exam Questions
- What is the role of saliva in digestion? Saliva contains amylase for starch digestion and lubricates food.
- How does the stomach aid in digestion? The stomach churns food mechanically and uses gastric juice for chemical digestion.
- What is the function of villi in the small intestine? Villi increase surface area for nutrient absorption.
What Examiners Usually Test
- Understanding of mechanical vs. chemical digestion.
- The role of different organs and enzymes in digestion.