Overview
This lecture explains the structure, function, and importance of enzymes as biological catalysts, including how they work, optimum conditions, and everyday uses.
What Are Enzymes?
- Enzymes are proteins that speed up chemical reactions in processes like photosynthesis, respiration, and protein synthesis.
- They are biological catalysts that lower activation energy and remain unchanged after reactions, allowing reuse.
- Some enzymes break down large molecules; others build them up or convert molecules into new forms.
How Enzymes Work
- Enzymes interact with substrates at the enzyme's active site, where the substrate fits in a lock and key mechanism.
- Collision theory states reactions occur when enzymes and substrates collide with enough energy and the correct orientation.
- Enzymes are specific: their active site only fits certain substrates.
Types and Examples of Enzymes
- Protease breaks down proteins into amino acids.
- Carbohydrase breaks down carbohydrates into glucose.
- Lipase breaks down fats into fatty acids and glycerol.
- Catalase breaks down harmful hydrogen peroxide into water and oxygen.
- Pectinase breaks down fruit cell walls to increase juice yield.
Factors Affecting Enzyme Activity
- Enzyme activity depends on sufficient substrate concentration; too little slows the reaction.
- Too much product can slow reaction rates by reducing collisions between enzyme and substrate.
- Each enzyme has optimum temperature and pH conditions for best activity.
- Higher temperatures generally increase reaction rates until enzymes denature above a specific threshold.
- Enzymes in different environments (like the stomach) have different optimum pH values.
- Sufficient enzyme concentration is needed for optimal reaction rates.
Everyday Uses of Enzymes
- Protease and lipase are used in biological washing powders to remove protein and fat stains from clothes.
- Enzymes are used in the food and drink industry, such as pectinase in fruit juice production.
Key Terms & Definitions
- Enzyme — a protein that acts as a biological catalyst to speed up chemical reactions.
- Substrate — the molecule that an enzyme acts upon.
- Active Site — the part of the enzyme where the substrate binds.
- Lock and Key Mechanism — model explaining enzyme specificity for substrates.
- Denaturation — loss of enzyme structure and function due to extreme temperature or pH.
Action Items / Next Steps
- Review the effects of pH and temperature on enzyme denaturation in the next lesson.