Respiring without air

The idea

In the absence of oxygen, as in yeast during fermentation, pyruvate is converted into ethanol and carbon dioxide; this is anaerobic respiration.

Yeast without air

Yeast is a tiny fungus. Imagine yeast cells in a place with no air (oxygen).

Can the yeast still get energy from its food?

• Yes, by a way that does not use oxygen
• No, it needs oxygen
• It gets energy from sunlight

Fermentation

Press Next step.

No air needed

When there is no oxygen, yeast can still break down pyruvate. It converts the pyruvate into ethanol and carbon dioxide. This happens during fermentation. Because it takes place without air, it is called anaerobic respiration.

In the absence of oxygen, as in yeast during fermentation, pyruvate is converted into ethanol and carbon dioxide; this is anaerobic respiration.

Notes

Without oxygen, as in yeast during fermentation, pyruvate becomes ethanol and carbon dioxide: anaerobic respiration.

Check yourself

In yeast during fermentation, pyruvate is converted into ...

Respiration that takes place in the absence of oxygen is called ...

In which organism does the book describe pyruvate being converted into ethanol and carbon dioxide?

• ethanol and carbon dioxide — correct. Yes!
• carbon dioxide and water. Carbon dioxide and water are the products when pyruvate is broken down using oxygen.
• lactic acid. Lactic acid is formed when muscle cells lack oxygen.
• aerobic respiration. Aerobic respiration takes place in the presence of air (oxygen).
• anaerobic respiration — correct. Yes!
• photosynthesis. Photosynthesis makes carbohydrates from carbon dioxide and water; it is not respiration.
• A green plant in sunlight. A green plant in sunlight makes carbohydrates by photosynthesis.
• A muscle cell lacking oxygen. In muscle cells lacking oxygen, pyruvate is converted into lactic acid.
• Yeast — correct. Yes!