BREATHING AND EXCHANGE OF GASES

Why oxygen (O₂) is essential to organisms

It is used to indirectly break down molecules like glucose, amino acids, and fatty acids to derive energy for activities.

What is released during catabolic reactions besides energy?

Carbon dioxide (CO₂)—harmful to the body.

What is a catabolic reaction?

A metabolic process where complex molecules are broken down into simpler ones, releasing energy, such as carbohydrates, fats, and proteins.

Define a metabolic process.

All the chemical reactions in a living organism that maintain life. These processes convert food into energy and building blocks for growth.