Transport of Materials

1. Transport of Materials Passive Transport

2. Passive Transport • Movement of materials that does not require energy from the cell. • Cell membranes are selectively permeable • Allows only certain materials to pass through • Particles move across a concentration gradient • Move from an area of high concentration to an area of low concentration.

3. Simple Diffusion • Movement of small particles directly through the plasma membrane • Speed of diffusion depends on • Temperature • Faster at higher temperatures • Difference in concentrations • Faster with greater difference • Molecules move until dynamic equilibrium is reached • State of balance where particles are equal in concentration in all directions.

4. Facilitated Diffusion • Movement of larger molecules or charged ions through protein channels • Ions are molecules in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative charge. • Essential chemicals travel this way glucose, sodium ions, chloride ions

5. Facilitated Diffusion – Cont’d • Pore proteins • Allows passage of small ions across concentration gradient • Carrier Proteins • Special protein gates openand closeto allow passage.

6. Osmosis • Diffusion of water • Semi-permeable membrane prevents movement of solute molecules • Water molecules move to even out the concentrations

7. Osmosis cont’d • Osmosis occurs whenever there is a solute concentration difference • Special terms used to compare solutions • Isotonic - two solutions with the same solute concentration • Hypertonic – a solution with a higher solute concentration • Hypotonic – a solution with a lower solute concentration.

8. Osmosis – cont’d • What happens to cells placed in solutions? • Animal cells • Plant cells