Overview
This lecture explains how the enzyme sucrase catalyzes the hydrolysis of sucrose into glucose and fructose on the intestinal microvilli.
Location and Role of Sucrase
- Sucrase is an enzyme found on the surface of microvilli in the intestinal epithelial mucosal cells.
- Microvilli increase the surface area of the small intestine for nutrient absorption.
Enzyme Catalysis of Sucrose Hydrolysis
- Sucrase catalyzes the hydrolysis (breakdown using water) of sucrose, a disaccharide, into two monosaccharides: glucose and fructose.
- The sucrose molecule binds to the active site of sucrase, causing the enzyme to change shape.
- The bond (oxygen bridge) between the glucose and fructose is exposed to water.
- A water (Hâ‚‚O) molecule breaks this bond, adding OH to one monosaccharide and H to the other.
- This process splits sucrose into glucose (blood sugar) and fructose (fruit sugar).
Enzyme Reusability and Limitation
- After the reaction, sucrase returns to its original shape and is available to catalyze more reactions.
- The cycle can repeat until the enzyme is denatured (loses shape), inhibited, or wears out.
Key Terms & Definitions
- Enzyme — a protein that speeds up (catalyzes) biochemical reactions.
- Sucrase — an enzyme that breaks down sucrose into glucose and fructose.
- Microvilli — microscopic projections on cells that increase surface area for absorption.
- Hydrolysis — a chemical reaction that splits molecules using water.
- Disaccharide — a sugar made of two monosaccharide units (e.g., sucrose).
- Monosaccharide — a single sugar molecule (e.g., glucose, fructose).
- Active site — the region on an enzyme where the substrate binds and the reaction occurs.
- Denatured — when an enzyme loses its shape and function.
Action Items / Next Steps
- Review the process of enzyme-catalyzed hydrolysis with sucrose as an example.
- Study diagrams showing enzyme-substrate interactions on microvilli.