AQA Biology 4.4.2.1

Anaerobic respiration

When oxygen runs short, cells still respire, but differently. Compare all three, then put yeast to work.

Combined Science · Higher tier

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Burning legs, rising dough.

Sprint flat out and your legs start to burn. Leave bread dough somewhere warm and it puffs up.

If you had to guess, do both of these happen with plenty of oxygen, or without enough oxygen?

Three ways to respire

If insufficient oxygen is supplied, cells respire anaerobically. Compare the three. Pick a column.

Aerobic respiration uses oxygen. Glucose is completely oxidised, so much more energy is transferred.

in muscles: glucose lactic acid

in plant and yeast cells: glucose ethanol + carbon dioxide

What happens to the lactic acid afterwards: in Response to exercise.

Fermentation

Anaerobic respiration in yeast cells is called fermentation. It is of economic importance in making bread and alcoholic drinks. Pick one.

Yeast in the dough respires anaerobically. The carbon dioxide makes bubbles, so the dough rises. The ethanol evaporates when it is baked.

Think again · yeast

“Yeast makes lactic acid.”

Your call

Choose

What does yeast make when it respires anaerobically?

Sort

Place each statement.

Tap a card, then tap the box it belongs in. Tap a placed card to take it back.

Command words in this lesson

Key fact

Anaerobic respiration: glucose gives lactic acid in muscles, or ethanol + carbon dioxide in plants and yeast. Much less energy is transferred.

Key note · AQA 4.4.2.1

If insufficient oxygen is supplied, cells respire anaerobically.
In muscles: glucose gives lactic acid.
In plant and yeast cells: glucose gives ethanol + carbon dioxide. In yeast this is fermentation, used to make bread and alcoholic drinks.
The oxidation of glucose is incomplete, so much less energy is transferred than in aerobic respiration.

Photograph this card. Tomorrow, cover it and say each line first.

Not sure which product goes with which?

Drawings are schematic.