What is meant by the term diffusion? Molecules of carbon dioxide diffuse from the air into the mesophyll cells - AQA - GCSE Biology - Question 8 - 2020 - Paper 1

The two changes that will increase the rate of diffusion are:

• Increased carbon dioxide concentration in the air
• Increased number of stomata that are open

The human lungs are designed to facilitate efficient gas exchange through several adaptations:

1. Large Surface Area: The lungs contain millions of alveoli, which provide a vast surface area for gas exchange, allowing more oxygen and carbon dioxide to diffuse across.

2. Thin Walls: The walls of the alveoli are thin (one cell thick), minimizing the distance that gases must diffuse, which speeds up the process of diffusion.

3. Good Blood Supply: A dense network of capillaries surrounds the alveoli, ensuring that oxygen is quickly absorbed into the bloodstream while carbon dioxide is rapidly expelled.

4. Maintaining Concentration Gradients: Breathing in fresh air increases oxygen concentration in the alveoli, while exhaling removes carbon dioxide, helping to maintain the concentration gradient necessary for efficient diffusion.

Osmosis

Nitrate ions are transported into the root hair cell through active transport. This process requires energy to move nitrate ions against their concentration gradient, from a lower concentration in the soil to a higher concentration in the root hair cell.