1. Movement of Materials Through The Cell Membrane For a cell to maintain its internal environment, (i.e., achieve homeostasis) it has to be selective in the materials it allows to cross its cell membrane. Transport: How molecules and fluids pass through the cell membrane.

2. Movement of Materials Through The Cell Membrane Movement of molecules across the cell membrane depends on: (A) concentration difference (B) membrane permeability (C) size and type of particle (D) temperature and pressure

3. Movement of Materials Through The Cell Membrane Three types of passive transport (i.e., no energy is required). 1. Diffusion: The process by which molecules of a substance move from an area of higher concentration of that substance to areas of lower concentrations.

4. Movement of Materials Through The Cell Membrane: Diffusion

5. Movement of Materials Through The Cell Membrane 2. Facilitated diffusion: The use of carrier proteins to move lipid insoluble substances through the cell membrane. Like diffusion and osmosis, no energy is used, but a concentration difference must exist for movement to occur. Example, transport of glucose.

6. Movement of Materials Through The Cell Membrane: Facilitated Diffusion

7. Movement of Materials Through The Cell Membrane 3. Osmosis: The diffusion of water molecules through a selectively permeable membrane from an area of higher concentration of water to an area of lower concentration of water. It continues until equilibrium is reached. Aquaporins are water channel proteins that allow water to pass through cell membranes.

8. Movement of Materials Through The Cell Membrane: Osmosis

9. Osmosis Osmotic pressure is the force caused by the net movement of water by osmosis. Two adjacent solutions are isotonic if they have the same concentrations of solute. Hypertonic solutions have a higher concentration of solute compared to another solution. Hypotonic solutions have a lower concentration of solute compared to another solution.