Anaerobic Respiration and Fermentation Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Compare anaerobic respiration to aerobic respiration, learn the equations for anaerobic respiration in muscles and yeast cells, and discover the economi...

• Compare aerobic and anaerobic respiration in terms of oxygen requirement, products and relative energy transfer
• Write word equations for anaerobic respiration in muscles and yeast cells
• Explain why anaerobic respiration transfers less energy than aerobic respiration
• Describe the economic importance of fermentation in bread and alcohol production

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 Anaerobic Respiration and Fermentation before testing yourself from memory.

• Picture yourself sprinting for the bus. Your muscles are working flat out, demanding energy faster than your lungs can supply oxygen. What happens next isn't your body giving up — it's switching to emergency mode.
• When cells can't get enough oxygen for aerobic respiration, they don't stop making energy. They switch to anaerobic respiration — literally 'without air'. It's less efficient, but it keeps you moving when oxygen runs short.
• Cellular respiration that occurs without oxygen, producing different waste products and transferring less energy than aerobic respiration
• Trap: Many students think anaerobic respiration only happens during exercise. Actually, it happens whenever oxygen supply can't meet demand — in waterlogged plant roots, deep muscle tissue, or rapidly dividing cells.
• Not all anaerobic respiration is the same. Your muscle cells do it one way, yeast cells do it completely differently. The starting point is identical — glucose — but the end products tell very different stories.
• In your muscles during intense exercise, glucose breaks down to form lactic acid. This is why your muscles burn and feel heavy after sprinting. The equation is deceptively simple:
• Used when oxygen supply cannot meet energy demand in muscle cells
• But in yeast cells and plant cells, something different happens. Instead of lactic acid, they produce ethanol and carbon dioxide:
• Occurs in yeast cells and waterlogged plant roots
• Anaerobic respiration in yeast cells that produces ethanol and carbon dioxide, used commercially in brewing and baking

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.