Enzymes – Biological Catalysts of Life
Enzymes are specialized protein molecules that act as biological catalysts, speeding up biochemical reactions without being consumed in the process.
Table of Contents
- What are Enzyme?
- Structure of Enzymes
- Types of Enzymes
- Functions of Enzyme
- Mechanism of Enzyme Action
- Factors Affecting Enzyme Activity
- MCQs & Practice Questions
- FAQs on Enzymes
What are Enzymes?
Enzyme are proteinaceous biological catalysts that increase the rate of chemical reactions in living cells by lowering the activation energy.
According to Encyclopaedia Britannica , enzyme are essential for metabolism and life processes.
Structure of Enzymes
The structure of enzyme is directly related to their function. Most enzyme are globular proteins with a specific three-dimensional shape.
Primary Structure
Linear sequence of amino acids linked by peptide bonds.
Secondary Structure
α-helices and β-pleated sheets stabilized by hydrogen bonds.
Tertiary Structure
The folded 3D structure forming the active site of the enzyme.
Quaternary Structure
Association of two or more polypeptide chains (e.g., DNA polymerase).
Types (Based on Function)
- Oxidoreductase Enzyme: Oxidation-reduction reactions
- Transferase Enzyme: Transfer of functional groups
- Hydrolase Enzyme: Hydrolysis reactions (e.g., amylase)
- Lyase Enzyme: Bond breaking without ATP
- Isomerase Enzyme: Isomerization reactions
- Ligase Enzyme: Bond formation using ATP
Functions
- Speed up metabolic reactions
- Digest food (amylase, pepsin, lipase)
- Synthesize DNA and proteins
- Regulate cellular activities
- Maintain homeostasis
Mechanism of Enzyme Action
Lock and Key Model of Enzyme Action
The substrate fits exactly into the enzyme’s active site.
Induced Fit Model of Enzyme Action
The enzyme changes shape slightly to accommodate the substrate.
Factors Affecting Enzyme Activity
- Temperature: High temperature denatures enzymes
- pH: Each enzyme has an optimum pH
- Substrate Concentration
- Enzyme Concentration
- Inhibitors
MCQs (NEET / CBSE)
Q1. Enzyme are chemically:
a) Carbohydrates b) Lipids c) Proteins d) Vitamins
Answer: c) Proteins
Q2. Enzyme increase reaction rate by:
Answer: Lowering activation energy
FAQs
Why are enzyme called biological catalysts?
Because they speed up biochemical reactions without being consumed.
What happens when enzyme are denatured?
They lose their shape and catalytic activity.
