2.41B Gas Exchange in Relation to Respiration & Photosynthesis (Edexcel IGCSE Biology)

• The processes of respiration and photosynthesis both rely on the exchange of oxygen and carbon dioxide

Gas exchange during respiration

• All living cells respire
• The process requires the uptake of oxygen and the release of carbon dioxide

The respiration equation

• The oxygen diffuses down the concentration gradient from a high concentration (outside the leaf) to a low concentration (inside the leaf)
  • The cells use oxygen in respiration so the concentration is always low inside the respiring cells

• The carbon dioxide diffuses down the concentration gradient from a high concentration (inside the leaf) to a low concentration (outside the leaf)

In respiration, carbon dioxide diffuses out of the leaf and oxygen diffuses into the leaf

Gas exchange during photosynthesis

• Plant cells photosynthesize when there is enough sunlight
• The process requires the uptake of carbon dioxide and the release of oxygen

The photosynthesis equation

• The carbon dioxide diffuses down the concentration gradient from a region of high concentration (outside the leaf) to a region of low concentration (inside the leaf)
  • The cells use carbon dioxide in photosynthesis so the concentration is always low inside the photosynthesizing cells

• The oxygen diffuses down the concentration gradient from a high concentration (inside the leaf) to a low concentration (outside the leaf)

In photosynthesis, carbon dioxide diffuses into the leaf and oxygen diffuses out of the leaf