Respiration is chemistry
Show on a big screenDough with yeast left overnight starts to bubble. Yeast is a tiny living thing. It releases energy without air. The bubbles are carbon dioxide gas.
Glucose is a sugar. Mitochondria are tiny parts inside a cell. Lactic acid and ethanol are two chemicals made from glucose.
- Glucose can break down two ways.
- With oxygen, in the mitochondria: much energy.
- Without oxygen, the cell still breaks it down.
- In a tired muscle: lactic acid forms.
- In yeast: ethanol and carbon dioxide form.
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Tap each cell. Read what it makes from glucose.
The rule
Respiration happens inside cells. The first step turns glucose into pyruvate. Pyruvate is a smaller molecule, with three carbon atoms. This step happens in the cytoplasm, the fluid inside a cell. Then one of three routes follows. A route is one way the breakdown can go.
Respiration breaks glucose down to release energy. Aerobic respiration uses oxygen and releases much more energy. Anaerobic respiration works without oxygen.
Aerobic route: glucose + oxygen → carbon dioxide + water + energy. This route ends in the mitochondria.
Anaerobic routes: in yeast, glucose → ethanol + carbon dioxide + energy. In muscle, glucose → lactic acid + energy.
The energy is used to make ATP, the cell’s energy currency. ATP carries energy to where the cell needs it.
Try the lab to finish this lesson.