Enzymes & Metabolism – CHEMASH Biology

Enzymes & Metabolism are biological catalysts that speed up chemical reactions in living organisms. Metabolism refers to all chemical reactions occurring inside cells. This topic is extremely important for Class 11 Biology, NEET 2026, Boards and competitive exams.

Related CHEMASH topics: Biomolecules Simplified | Cell Organelles & Functions

What are Enzymes?
Mechanism of Enzyme Action
Factors Affecting Enzyme Activity
Types of Enzymes
Metabolism
Anabolism vs Catabolism
Comparison Table
MCQs with Explanation
FAQs

What are Enzymes?

Enzymes are mostly proteins that act as catalysts and increase the rate of biochemical reactions without being consumed. They lower activation energy and make reactions faster.

Protein in nature (except ribozymes)
Highly specific
Reusable
Work best at optimum temperature & pH

Example: Amylase breaks down starch into sugars.

Mechanism of Enzyme Action

Enzymes work through the Lock and Key Model or Induced Fit Model.

Substrate binds to active site
Enzyme-substrate complex forms
Product forms and released
Enzyme remains unchanged

Reaction: Enzyme + Substrate → ES Complex → Product + Enzyme

Factors Affecting Enzyme Activity

Temperature: High temperature denatures enzymes.
pH: Each enzyme has optimum pH.
Substrate concentration: Rate increases up to saturation.
Enzyme concentration: More enzymes = faster reaction.
Inhibitors: Reduce enzyme activity.

Types of Enzymes

Oxidoreductases – Oxidation reactions
Transferases – Transfer functional groups
Hydrolases – Hydrolysis reactions
Lyases – Remove groups without hydrolysis
Isomerases – Rearrangement reactions
Ligases – Join molecules

What is Metabolism?

Metabolism is the sum total of all biochemical reactions occurring in living organisms. It includes both building-up and breakdown reactions.

Anabolism vs Catabolism

Process	Meaning	Energy	Example
Anabolism	Building complex molecules	Requires energy	Protein synthesis
Catabolism	Breaking molecules	Releases energy	Respiration

Quick Comparison

Term	Main Function
Enzymes	Speed up reactions
Metabolism	Total chemical reactions
Anabolism	Build molecules
Catabolism	Break molecules

MCQs with Explanation (NEET 2026)

1. Enzymes are mainly composed of:
Answer: Proteins
Explanation: Most enzymes are protein molecules.

2. Breakdown reactions are called:
Answer: Catabolism
Explanation: Catabolic reactions release energy.

3. Site where substrate binds enzyme?
Answer: Active Site
Explanation: Substrate fits specifically into active site.

FAQs

Q1. Do enzymes get consumed during reaction?
A: No, enzymes remain unchanged.

Q2. Why are enzymes specific?
A: Because active site shape matches only specific substrates.

Official reference: NCERT Biology Textbook

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Enzymes & Metabolism