Study Notes
Transport in cells involves the movement of substances across cell membranes, which can occur through diffusion, osmosis, or active transport. These processes are essential for maintaining cellular functions and homeostasis.
- 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 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 cells, making them turgid.
- 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 by root hair cells in plants.
Exam Tips
Key Definitions to Remember
- Diffusion is the movement of molecules from high to low concentration.
- Osmosis is the movement of water across a membrane from high to low water potential.
- Active transport requires energy to move substances against a concentration gradient.
Common Confusions
- Confusing diffusion with osmosis, which specifically involves water.
- Thinking active transport does not require energy.
Typical Exam Questions
- What is diffusion? Movement of molecules from high to low concentration.
- How does osmosis differ from diffusion? Osmosis specifically involves water moving across a membrane.
- What is required for active transport? Energy from respiration.
What Examiners Usually Test
- Understanding of how substances move in and out of cells.
- Differences between diffusion, osmosis, and active transport.
- Examples of where these processes occur in living organisms.