Enzymes

Definition

Enzymes are biological catalysts that speed up chemical reactions in living organisms without being consumed.

Structure of Enzymes

• Proteins made of amino acids.
• Have an active site where substrate binds.
• Substrate-specific (lock and key model or induced fit).

Types of Enzymes

• Amylases: Break down starch into sugars (e.g., salivary amylase).
• Proteases: Break down proteins into amino acids (e.g., pepsin).
• Lipases: Break down fats into fatty acids and glycerol (e.g., pancreatic lipase).
• Other enzymes: Catalase, lactase, sucrase, etc.

Factors Affecting Enzyme Activity

• Temperature: each enzyme has an optimum temperature.
• pH: each enzyme has an optimum pH.
• Substrate concentration: increased substrate increases rate up to saturation.
• Enzyme concentration: more enzymes can increase the rate if substrate is available.
• Inhibitors: substances that decrease enzyme activity.

Importance of Enzymes

• Aid digestion (amylase, protease, lipase).
• Essential in metabolic reactions.
• Used in industrial processes (fermentation, detergents).

Practice Questions

• Define enzymes and explain their role as biological catalysts. (4 marks)
• Describe the structure of an enzyme and explain the lock and key model. (5 marks)
• List three types of enzymes and state their function with examples. (6 marks)
• Explain five factors that affect enzyme activity. (5 marks)
• Short answer: Name one enzyme found in saliva and state its function. (2 marks)