Anaerobic respiration Flashcards – Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028)

What is anaerobic respiration?

Chemical reactions in cells that break down nutrient molecules and release energy without using oxygen.

How does the energy released per glucose molecule compare between anaerobic and aerobic respiration?

Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration.

What two products are formed when yeast breaks down glucose by anaerobic respiration?

Alcohol and carbon dioxide.

What product is formed when muscles break down glucose by anaerobic respiration during vigorous exercise?

Lactic acid.

What is the balanced chemical equation for anaerobic respiration in yeast?

$\ce{C6H12O6 -> 2C2H5OH + 2CO2}$

What do the coefficients in the equation for anaerobic respiration in yeast tell you about the molecules involved?

One glucose molecule produces two ethanol molecules and two carbon dioxide molecules.

What must be equal on both sides of the balanced equation for anaerobic respiration in yeast?

The number of atoms of each element: carbon, hydrogen and oxygen.

How does vigorous exercise cause an oxygen debt?

Anaerobic respiration in muscles produces lactic acid, which builds up in the muscles and blood.

Why does heart rate remain fast after vigorous exercise?

To transport lactic acid in the blood from the muscles to the liver.

Why does breathing remain deeper and faster after vigorous exercise?

To supply oxygen so that lactic acid can be respired aerobically in the liver.

How is the oxygen debt removed after vigorous exercise?

Lactic acid is transported to the liver and respired aerobically using oxygen.