Study Notes
Movement in and out of cells involves processes like diffusion and osmosis, which are essential for transporting substances across cell membranes.
- Diffusion — The net movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient. Example: Oxygen diffusing from alveolar air spaces into blood in capillaries.
- Osmosis — The diffusion of water molecules through a partially permeable membrane from a region of high water potential to low water potential. Example: Water moving into plant root cells from the soil.
- Concentration Gradient — The difference in concentration of a substance across a space or a membrane. Example: Greater concentration of carbon dioxide in the blood than in alveolar air spaces.
- Surface Area to Volume Ratio — A factor that influences the rate of diffusion; larger surface areas allow for more efficient diffusion. Example: Root hair cells have increased surface area for absorption.
Exam Tips
Key Definitions to Remember
- Diffusion: Movement of molecules from high to low concentration.
- Osmosis: Movement of water through a partially permeable membrane from high to low water potential.
- Concentration Gradient: Difference in concentration across a space.
Common Confusions
- Confusing diffusion with osmosis; remember osmosis specifically involves water.
- Misunderstanding the role of concentration gradients in diffusion and osmosis.
Typical Exam Questions
- What is diffusion? Movement of molecules from high to low concentration.
- How does osmosis differ from diffusion? Osmosis involves water moving through a partially permeable membrane.
- Why is surface area important for diffusion? Larger surface areas allow for more efficient diffusion.
What Examiners Usually Test
- Understanding of diffusion and osmosis processes.
- Ability to explain the effects of concentration gradients.
- Application of concepts to experimental results.