Respiration (Cambridge (CIE) IGCSE Biology)

Respiration is a chemical reaction that takes place in living cells. It releases energy from glucose.

Living organisms use the energy released during respiration in many ways, including:

• muscle contraction

• protein synthesis

• cell division

• active transport

• growth

• nerve impulse transmission

• maintaining a constant body temperature

Variables that would need to be controlled in an investigation into the effect of temperature on respiration in yeast include:

• volume of yeast suspension

• number of cells present in the yeast suspension

• type of sugar provided

• concentration of sugar solution

• pH

• availability of oxygen

(Avoid saying 'amount')

An increase in temperature would cause an increase in the rate of respiration in yeast cells.

This trend would continue until around 40°C, above which the rate of respiration would slow down due to denaturing enzymes.

Aerobic respiration is a cellular reaction that uses oxygen to break down nutrients in order to release energy.

The word equation for aerobic respiration is:

glucose + oxygen → carbon dioxide + water

The reactants in aerobic respiration are glucose and oxygen.

The balanced chemical equation for aerobic respiration is:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Anaerobic respiration is the chemical reaction in cells that breaks down nutrient molecules to release energy in the absence of oxygen.

False.

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