B3.1 - Movement of Molecules In and Out of cells

Diffusion
1. Particles move from an area of high concentration to low
  Nota:
  - For example, different gases can simply diffuse through one another. Alternatively, dissolved particles can diffuse in and out of cells through cell membranes.
2. The structure of leaves let gases diffuse in and out of cells
3. Diffusion through cell membranes
  1. Gas exchange happens in the lungs
  2. The villi provide a really really big surface area
Osmosis
1. Similar to diffusion, but only refers to water
  1. Water moves across a partially permeable membrane (eg. cell membrane) from an area of high water concentration to low
Active Transport
1. Root hairs are specialised for absorbing water and minerals
2. Sometimes substances need to be absorbed against a concentration gradient - ie. from a lower to higher concentration
3. Root hairs take in minerals using active transport
4. We need active transport to stop us starving

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