WHAT IS RESPIRATION AND ITS TYPES | Biology | Respiration In Animals

Learning Objectives for the Lesson on Respiration

By the end of the lesson, students should be able to:

Knowledge Objectives

Define respiration and explain how it differs from breathing.
Identify and describe the two types of respiration: aerobic and anaerobic.
State the word and chemical equations for aerobic and anaerobic respiration.
Explain ATP (Adenosine Triphosphate) as the energy molecule produced during respiration.

Understanding Objectives

Differentiate between aerobic and anaerobic respiration based on:
- oxygen use
- products formed
- amount of energy released
- where they occur in the cell
Explain the importance of respiration to living organisms.
Interpret chemical equations of respiration correctly.
Illustrate or trace where aerobic and anaerobic respiration occur in the cell (mitochondria and cytoplasm).
Appreciate the importance of energy in carrying out daily activities such as movement, growth, and repair.
Develop curiosity about how the body produces and uses energy.

1. Meaning / Definition of Respiration

Respiration is the biological process by which living organisms release energy from food substances (like glucose).
It involves the breakdown of glucose in the presence or absence of oxygen to produce energy (ATP) that the body uses for growth, movement, repair, and other activities.

Key points:

Respiration takes place in all living cells.
It is not the same as breathing.
Breathing is the physical act of inhaling and exhaling air, but respiration is the chemical process inside the cells.
The main food substance used is glucose.

2. Types of Respiration

There are two major types:

A. Aerobic Respiration

This is respiration that uses oxygen to break down glucose completely into carbon dioxide and water.

Detailed explanation:

Occurs inside the mitochondrion of the cell.
Produces large amount of energy (ATP).
Common in humans, animals, plants, and most organisms.

Characteristics of aerobic respiration:

Requires oxygen
Complete breakdown of glucose
Produces high energy
Produces carbon dioxide and water
Takes place continuously in most organisms

B. Anaerobic Respiration

This is respiration that does NOT use oxygen to break down glucose. Instead, glucose is only partly broken down.

Detailed explanation:

Occurs in the cytoplasm of the cell.
Produces less energy than aerobic respiration.
Common in yeast, bacteria and occurs in humans during vigorous exercise.

Types of anaerobic respiration:

In animals (e.g., human muscles):
Glucose is converted into lactic acid and energy.
In yeast (fermentation):
Glucose is converted into alcohol (ethanol), carbon dioxide, and energy.

Characteristics of anaerobic respiration:

Does not require oxygen
Occurs when oxygen is insufficient
Produces little energy
Leads to lactic acid build-up in muscles (causing cramps)

3. Word and Chemical Equations of Respiration

A. Aerobic Respiration

Word Equation:

Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)

Chemical Equation:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

B. Anaerobic Respiration in Human Muscle

Word Equation:

Glucose → Lactic acid + Energy

Chemical Formula Summary (simplified):

C₆H₁₂O₆ → 2C₃H₆O₃ + Energy

C. Anaerobic Respiration in Yeast (Fermentation)

Word Equation:

Glucose → Alcohol (Ethanol) + Carbon dioxide + Energy

Chemical Formula Summary (simplified):

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + Energy

4. Energy Production (ATP)

ATP stands for Adenosine Triphosphate.
It is the energy-carrying molecule produced during respiration.

How ATP Works

Think of ATP as the “energy currency” of the cell.
Whenever the body needs energy (to move, grow, repair cells, send nerve impulses, etc.), ATP releases energy by breaking one phosphate bond.
Aerobic respiration produces about 36–38 ATP molecules from one glucose molecule.
Anaerobic respiration produces only 2 ATP molecules.