Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Mechanical digestion is the physical breakdown of food into smaller pieces without changing its chemical nature. This increases the surface area for enzyme action and occurs via chewing in the mouth, churning in the stomach, and emulsification by bile in the small intestine.
Chemical digestion involves the breakdown of large, insoluble molecules into small, soluble molecules through the action of enzymes and water ().
The stomach maintains a low (approx ) using hydrochloric acid (), which serves to denature proteins and provide the optimum for the protease enzyme pepsin.
Bile is produced in the liver and stored in the gallbladder; it contains bile salts that emulsify fats, increasing the surface area for lipase, and contains to neutralize the acidic chyme coming from the stomach.
The small intestine produces enzymes such as maltase to finish the digestion of carbohydrates into (glucose), which is small enough to be absorbed into the bloodstream.
Enzymes are biological catalysts. Their activity is highly dependent on environmental factors, specifically temperature and , where extreme deviations lead to the denaturation of the enzyme's active site.
📐Formulae
💡Examples
Problem 1:
Describe the effect of on the activity of Pepsin and Trypsin enzymes found in the human digestive system.
Solution:
Pepsin works optimally at a of approximately in the stomach. Trypsin, found in the small intestine, works optimally at a slightly alkaline of approximately .
Explanation:
Pepsin is adapted to the acidic environment created by in the stomach. When food moves into the duodenum, bile and pancreatic juice neutralize the acid, raising the to around , which would denature pepsin but is the ideal for trypsin.
Problem 2:
Explain how mechanical digestion by teeth aids the chemical digestion of starch.
Solution:
Teeth break down large food particles into smaller ones, significantly increasing the ratio.
Explanation:
By increasing the total surface area of the food, more starch molecules are exposed on the surface of the particles. This allows the enzyme amylase to collide more frequently with the substrate, increasing the rate of the reaction .
Problem 3:
What is the role of bile in the digestion of lipids?
Solution:
Bile emulsifies large fat globules into smaller droplets and neutralizes .
Explanation:
Emulsification is a mechanical process that increases the surface area of lipids. Since lipids are hydrophobic and clump together, lipase can only act on the surface. Smaller droplets mean a faster rate of into fatty acids and glycerol.