Mito Rush

Mito Rush: aerobic and anaerobic respiration

This free game is part of our Pearson Edexcel iGCSE Biology (4BI1) course for exams in EXAM YEARS 2026-2029.

What is respiration?

Respiration is a chemical reaction that happens inside every living cell, all the time. It releases energy from glucose, which cells store as ATP and use for muscle contraction, building large molecules such as proteins, active transport, cell division and keeping warm.

Respiration is not the same as breathing. Breathing just moves air into and out of the lungs; respiration is the chemistry inside the cells. Plants and yeast respire too, even though they do not breathe.

The four rounds

• Mito Reactor: molecules orbit a 3D mitochondrion. Pick the reactants that go in, then the products that come out, and answer questions on the balanced symbol equation.
• Oxygen Sprint: race a rival. Sprinting drains your oxygen, so your muscles switch to anaerobic respiration and lactic acid builds up. Push too hard and you cramp. Pace your bursts to win.
• Yeast Bakery: every right answer makes more carbon dioxide bubbles and a bigger loaf, showing how yeast respires without oxygen.
• Portal Sort: drag each fact card into the aerobic or anaerobic portal and build a streak.

The equations you need

• Aerobic respiration (word equation): glucose + oxygen → carbon dioxide + water
• Aerobic respiration (balanced symbol equation): C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
• Anaerobic respiration in animals: glucose → lactic acid
• Anaerobic respiration in plants and yeast: glucose → ethanol + carbon dioxide

Aerobic vs anaerobic: the key differences

• Oxygen: aerobic respiration needs it; anaerobic respiration does not.
• Energy: aerobic respiration breaks glucose down completely, so it releases much more energy per glucose molecule. Anaerobic respiration only partly breaks glucose down and releases much less.
• Products: aerobic makes carbon dioxide and water. Anaerobic makes lactic acid in animals, or ethanol and carbon dioxide in plants and yeast.
• When it happens: your muscles switch to anaerobic respiration during hard exercise, when oxygen cannot reach them fast enough. Lactic acid builds up and causes fatigue.

Exam tips

• Never write that respiration "makes" or "produces" energy. Energy is released.
• Do not put oxygen into an anaerobic equation, or carbon dioxide into the animal version.
• Balance the symbol equation by counting atoms: 6 carbons make 6CO₂, 12 hydrogens make 6H₂O, and that needs 6O₂.
• In bread making, the carbon dioxide makes the dough rise; the ethanol evaporates when the bread is baked.