IB Biology Topic B3.1: Gas Exchange Key Definitions

The Bohr shift (or Bohr effect) describes how haemoglobin’s affinity for oxygen decreases in the presence of high levels of carbon dioxide (CO₂) or in acidic environments (lower pH).

The difference in concentration of a substance (e.g., oxygen or carbon dioxide) between two regions.

The process by which oxygen enters the body and carbon dioxide is expelled.

The ability of a substance (e.g., oxygen, carbon dioxide, or water) to pass through a membrane or surface.

Stomata are small openings on the leaf surface that regulate gas exchange and water loss in plants

Surfactant is a lipid-based substance that reduces surface tension in the alveoli, preventing the alveoli from collapsing after exhalation.

Transpiration is the loss of water vapor from the aerial parts of a plant, primarily through tiny pores in the leaves called stomata.

Ventilation is the process of moving air or water across the gas-exchange surface to refresh the supply of gases and maintain the concentration gradient.