Download Cell Membrane - Gatekeeper for the cell

Cell Membrane
- - - - - Gatekeeper for the cell
Controls the movement of materials in and out of the cell Permeable – allowing passage Impermeable – not allowing passage
Cells have a “selectively permeable” membrane
§ Will only allow some materials to pass through
- Membrane is made up of 2 layers of fat particles, with proteins embedded
- Proteins will act as channels for materials to pass through - - - - Fluid Movement – Diffusion Review of the particle theory
All particles are constantly moving
o Solid – are moving very slowly, and are tightly packed together
o Liquid – moving and are close together
o Gas – moving very quickly and are spaced very far apart
Diffusion – the movement of particles from an area of high concentration to an area of
low concentration
concentration gradient – the difference in concentration between 2 areas
this determines the direction of movement of the particles o diffusion will continue until
the areas are “equals”
Osmosis
- a special example of diffusion
o diffusion in water
o follows the same rules – concentration gradient - Turgor Pressure o Plants have large central vacuole in which water is stored
o When plants need water the vacuole releases the water for the plant to use
o When its used up, the plant starts to droop
o When water is available concentration gradient exists, so water is allowed into cell,
vacuole swells, causing pressure to be exerted out – turgor pressure – plants is
able to stand upright
Questions:
1. Use a diagram to describe the process of diffusion. Use the particle theory in
description.
2. What does concentration gradient mean (your own words)
3. How is the movement of particles in diffusion determined?
4. Give 2 examples of diffusion.
5. Explain how osmosis creates turgor pressure in plants.