Study Notes
Diffusion and osmosis are processes that describe the movement of particles in and out of cells.
- Diffusion — the movement of particles from an area of higher concentration to an area of lower concentration. Example: Oxygen moving into cells from the bloodstream.
- Osmosis — the movement of water molecules through a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration. Example: Water entering plant roots from the soil.
- Selectively Permeable Membrane — a barrier that allows certain substances to pass through while blocking others. Example: Cell membrane allowing water but not large molecules to pass.
Exam Tips
Key Definitions to Remember
- Diffusion: Movement of particles from high to low concentration.
- Osmosis: Movement of water through a selectively permeable membrane from low to high solute concentration.
- Selectively Permeable Membrane: Allows certain substances to pass while blocking others.
Common Confusions
- Confusing diffusion with osmosis, as both involve movement but differ in what is moving.
- Thinking osmosis involves solute movement, when it actually involves water movement.
Typical Exam Questions
- What is diffusion? Movement of particles from an area of higher concentration to an area of lower concentration.
- What is osmosis? Movement of water molecules through a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.
- How does a selectively permeable membrane function? It allows certain substances to pass through while blocking others.
What Examiners Usually Test
- Understanding the difference between diffusion and osmosis.
- Ability to explain how a selectively permeable membrane works.
- Examples of diffusion and osmosis in biological systems.