Study Notes
Movement in and out of cells involves processes like diffusion, osmosis, and active transport, which are essential for cellular function.
- Diffusion — the net movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient. Example: Oxygen moving from alveolar air spaces to 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.
- Active Transport — the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration. Example: Uptake of ions from soil water by root hair cells in plants.
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.
- Active Transport: Movement of particles from low to high concentration using energy.
Common Confusions
- Diffusion and osmosis both involve movement down a gradient, but osmosis specifically refers to water.
- Active transport requires energy, unlike diffusion and osmosis.
Typical Exam Questions
- What is diffusion? Movement of molecules from high to low concentration.
- How does osmosis affect plant cells in a hypertonic solution? Water moves out, causing plasmolysis.
- Why is active transport important in root hair cells? It allows uptake of ions against the concentration gradient.
What Examiners Usually Test
- Understanding of concentration gradients in diffusion and osmosis.
- Effects of osmosis on plant and animal cells.
- Role of energy in active transport.