BiologyAQA (7402)Exchange & Transport

Gas Exchange & Transport — AQA A-Level Biology

AQA A-Level Biology

Gas exchange and transport is a core topic in AQA A-Level Biology (Section 3.3). This interactive tool explores the structure of gas exchange surfaces — alveoli in mammals, gills in fish, and tracheae in insects — alongside the principles of Fick's law of diffusion. Visualise how surface area, diffusion distance, and concentration gradient affect exchange rates. The haemoglobin dissociation curve section lets you explore the Bohr effect and fetal haemoglobin interactively — essential for 25-mark essay questions on transport systems.

Uses Google Fonts (Crimson Pro, Karla). Requires an internet connection for full styling.

Frequently asked questions

What is Fick's law of diffusion?+

Fick's law states that the rate of diffusion is proportional to (surface area × concentration difference) ÷ thickness of the exchange surface. Gas exchange surfaces are adapted to maximise rate by having large surface area, thin walls, and maintaining steep concentration gradients.

What is the Bohr effect?+

The Bohr effect describes how an increase in carbon dioxide concentration (or decrease in pH) causes haemoglobin to release oxygen more readily. This shifts the oxygen-haemoglobin dissociation curve to the right, ensuring more oxygen is delivered to actively respiring tissues.

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