Why dough rises

The idea

Yeast, a fungus that grows well in warm conditions, respires and breaks down food for energy, releasing carbon dioxide bubbles that make dough soft and fluffy, and a little alcohol.

Dough that grows

Dough for bread is kept for a few hours and it becomes soft and fluffy. A microorganism called yeast is mixed into it. Yeast is a fungus.

What makes the dough soft and fluffy?

• Tiny bubbles of gas made by yeast
• Air that we blow into it
• Water that dries up

Warm place or cool place?

Leave the dough for some hours in both places. Then tap each bowl to read what happened.

Yeast breathes out bubbles

Yeast is a fungus that grows well in warm conditions. Like other organisms it respires and breaks down food to release energy. It releases carbon dioxide bubbles that make the dough soft and fluffy, and a little alcohol.

• Step | What happens
• 1 | Yeast respires and breaks down food for energy
• 2 | Carbon dioxide is released as bubbles
• 3 | The bubbles make the dough soft and fluffy
• Also | A small amount of alcohol forms, which gives the dough a slightly different smell

Notes

Yeast, a fungus, grows well in warm conditions. It breaks down food for energy and releases carbon dioxide bubbles that make dough soft and fluffy, and a little alcohol.

Check yourself

Which gas forms the bubbles in the dough?

What kind of microorganism is yeast?

Yeast grows well in warm conditions. Where will dough become soft and fluffy sooner?

• Carbon dioxide — correct. Yes. Yeast releases carbon dioxide as it breaks down food.
• Methane. Methane is the main gas in biogas, not in dough.
• Nitrogen. The bubbles in dough are carbon dioxide made by the yeast.
• A fungus — correct. Yes. Yeast is a unicellular fungus.
• A bacterium. Yeast is a fungus. Lactobacillus is a bacterium.
• A virus. A virus is not made of cells. Yeast is a living fungus.
• In a warm place — correct. Yes. Yeast grows well when it is warm.
• In a cool place. Yeast grows well in warm conditions, not cool ones.