Question map
What causes dough (a mixture of flour, water, etc.) to rise when yeast is added to it?
Explanation
Dough rises primarily due to the release of carbon dioxide gas during the process of fermentation. Yeast, a fungal microorganism, respires by breaking down sugars present in the flour [1]. In the absence of oxygen, yeast undergoes anaerobic respiration, converting glucose into ethanol and carbon dioxide. This carbon dioxide gas forms tiny bubbles or air pockets within the dough [1]. These bubbles are trapped by the gluten network created during kneading, causing the dough to expand and become soft and fluffy [2]. While temperature affects the rate of yeast activity and fermentation, it is the physical accumulation and expansion of the carbon dioxide gas itself that causes the dough to rise [1]. During baking, this gas expands further due to heat, contributing to the final leavened structure of the bread.
Sources
- [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Activity 2.8: Let us perform > p. 21
- [2] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.5 > p. 87