What is Metabolism? Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Understanding metabolism as the sum of all reactions in cells and how respiration provides energy for metabolic processes.

• Define metabolism as the sum of all reactions in a cell or organism
• Explain how respiration provides energy for metabolic processes
• Describe examples of metabolic reactions that build and break down molecules
• Apply knowledge of metabolism to explain how organisms maintain life processes

Key ideas to keep in view

Use this lesson to stay inside B1.3 Respiration while connecting the detail back to the wider B1: Cell level systems topic.

• B1: Cell level systems
• B1.3 Respiration
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from What is Metabolism? before testing yourself from memory.

• Right now, inside every cell in your body, thousands of chemical reactions are happening every second. Your cells are building proteins, breaking down food, making DNA, and powering muscle contractions. This non-stop chemical activity has a name: metabolism.
• Think of your body like a busy factory that never shuts down. Raw materials come in, products get made, waste gets removed, and energy powers the whole operation. That's metabolism in action.
• The sum of all chemical reactions that occur in a cell or organism. The energy from respiration is used for the continual enzyme-controlled processes of metabolism.
• Trap: Many students think metabolism only means 'how fast you burn calories'. Actually, metabolism includes ALL chemical reactions - building molecules, breaking them down, and everything in between.
• Metabolism includes reactions that build larger molecules and reactions that break larger molecules down.
• Reactions that build larger molecules from smaller ones.
• Reactions that break down larger molecules into smaller ones.
• Here's the clever bit: the energy released by catabolic reactions powers the anabolic reactions. It's like using the heat from burning old wood to forge new metal tools.
• All these metabolic reactions need energy to happen. But where does this energy come from? The answer is respiration - the process that releases energy from glucose in every living cell.
• The process that releases energy from glucose (and other molecules) to power metabolic reactions. Occurs in mitochondria and requires oxygen for maximum efficiency.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.