Summary
The movement of substances in and out of cells is essential for obtaining nutrients and eliminating waste. This process occurs through diffusion, osmosis, and active transport.
- Diffusion — movement of particles from high to low concentration. Example: Oxygen diffuses into cells during respiration.
- Osmosis — movement of water molecules from high to low water potential through a selectively permeable membrane. Example: Water enters plant cells, causing them to become turgid.
- Active Transport — movement of substances against the concentration gradient using energy. Example: Mineral absorption in plant roots.
Exam Tips
Key Definitions to Remember
- Diffusion: Movement of particles from high to low concentration.
- Osmosis: Movement of water from high to low water potential through a selectively permeable membrane.
- Active Transport: Movement of substances against the concentration gradient using energy.
Common Confusions
- Diffusion and osmosis both involve passive movement, but osmosis is specific to water.
- Active transport requires energy, unlike diffusion and osmosis.
Typical Exam Questions
- What happens to oxygen during respiration? Oxygen diffuses into cells from the blood.
- What happens to carbon dioxide during respiration? Carbon dioxide diffuses out of cells into the bloodstream.
- Why is osmosis considered a passive mechanism of transport? It does not require energy as water moves down its potential gradient.
What Examiners Usually Test
- Differences between diffusion, osmosis, and active transport.
- Examples of each transport mechanism in plants and animals.
- The role of selectively permeable membranes in osmosis.