10.2 Aerobic Respiration


2026 📋 Syllabus Objectives

By the end of these notes, you should be able to:

  1. Describe aerobic respiration as the release of a relatively large amount of energy by the breakdown of glucose in the presence of oxygen.
  2. State the word equation and balanced chemical equation for aerobic respiration.

What Is Respiration?

Respiration is a chemical process that happens inside every single living cell of every organism — including you. It is the way that living things release energy from food.

Think of respiration like burning fuel in a car engine. The car uses petrol to release energy and move. Your cells use glucose (a type of sugar) to release energy so they can do everything they need to do — move muscles, grow, repair cells, and stay alive.

⚠️ Common Mistake: Respiration is NOT the same as breathing. Breathing is the physical act of moving air in and out of your lungs. Respiration is a chemical reaction happening inside your cells. They are related, but they are not the same thing.


What Is Aerobic Respiration?

The word aerobic means "in the presence of oxygen." So, aerobic respiration is the type of respiration that requires oxygen.

Here is a simple, clear definition:

Aerobic respiration is the breakdown of glucose, using oxygen, to release a relatively large amount of energy.

Let's break this definition into three key parts:

Part of the DefinitionWhat It Means
Breakdown of glucoseGlucose molecules are split apart and broken down during the reaction
In the presence of oxygenOxygen must be available for this process to happen
Release of a relatively large amount of energyThis process releases much more energy than anaerobic (without oxygen) respiration

Where Does Aerobic Respiration Happen?

Aerobic respiration takes place inside cells — specifically in a part of the cell called the mitochondria (singular: mitochondrion). You can think of mitochondria as the "powerhouses" of the cell, because this is where most of the energy is released.

Every living organism — plants, animals, fungi, and bacteria — carries out respiration. It never stops, not even when you are asleep.

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