10.1 Respiration

2026 📋 Syllabus Objectives

By the end of this topic, you should be able to:

  1. Describe respiration as the chemical reactions in all living cells that release energy from glucose.
  2. State the uses of energy in living organisms, including muscle contraction, protein synthesis, cell division, active transport, growth, the passage of electrical impulses along neurones, and the maintenance of a constant body temperature.
  3. Investigate and describe the effect of temperature on respiration in yeast.

📖 Main Content

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1. What is Respiration?

Respiration is the process by which all living cells carry out a series of chemical reactions that break down glucose and release energy.

Think of it this way: glucose is like a battery, and respiration is the process that "unlocks" the energy stored inside it so the cell can actually use it.

Key points to remember:

  • Respiration happens inside every living cell — in animals, plants, fungi, and bacteria. Every single cell does it, all the time.
  • It is not the same as breathing. Breathing (also called ventilation) is just moving air in and out of your lungs. Respiration is a chemical process happening at the cellular level.
  • The raw material (the starting substance) for respiration is glucose — a type of sugar.
  • The energy released is used to power everything the organism needs to do.

💡 Simple definition to learn: Respiration = chemical reactions in living cells that release energy from glucose.

2. Uses of Energy in Living Organisms

The energy released during respiration is not wasted. It is used to power many essential processes inside the body. You need to know all seven of the following uses:

🔹 Muscle Contraction

  • Muscles are made of special fibres that can shorten (get shorter) and pull on bones to create movement.
  • Every time a muscle contracts (tightens), it needs energy.
  • Without energy from respiration, your muscles could not move — you could not walk, run, breathe, or even blink.
  • Example: When you kick a football, the muscles in your leg use energy to contract and swing your leg forward.

🔹 Protein Synthesis

  • Protein synthesis means making proteins — building new protein molecules inside cells.
  • Proteins are essential for almost everything: they build cells and tissues, act as enzymes (biological catalysts that speed up chemical reactions), form antibodies, and much more.
  • Building proteins requires energy.
  • Example: When your body repairs a cut on your skin, cells use energy to make new protein molecules to rebuild the damaged tissue.

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