Cellular Transport All materials entering or leaving the cell must pass through which organelle?  Cell Membrane

 Function  Provides support and protection  Semipermeable membrane that regulates what molecules and ions enter and leave the cell  Keeps the cell in a stable state called homeostasis  Cell recognition  Structure  Flexible, double-layered sheet called a lipid bilayer a.Comprised of hydrophilic phosphate heads and hydrophobic hydrocarbon tails

 Proteins embedded in the bilayer act as channels and pumps that help move materials across the cell membrane  Carbohydrates attached to the proteins act as chemical ID cards, allowing cells to identify each other  Draw Figure 7-12 on page 182 in your textbook Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

C.Factors affecting membrane permeability 1.Size 2.Solubility in lipids 3.Ionic charge 4.Presence of carrier proteins

Do you understand the concept of concentration ? What is the concentration of the above solution? –20% Sugar solution What is the solvent? –Water What is the solute? –Sugar How can I make the solution more concentrated? –Add more sugar or less water Why don’t we call this an 80% water solution?

II.Passive Processes - No energy required A.Diffusion- movement of molecules from an area of high concentration to low. B.Facilitated Diffusion - Carrier proteins assist the diffusion of materials (e.g. glucose) Which way will the ammonia flow?

Diffusion Movie

Which way will the water flow? H2OH2O H2OH2O H2OH2O C.Osmosis - The movement of water through a selectively permeable membrane in the direction of the highest solute concentration (aka - the diffusion of water).

Osmosis Movie  DRAW FIG 7-16, pg. 186

III.Active Processes - energy required A.Active Transport - the movement of molecules across membrane from low concentrations to higher concentrations (against the concentration gradient). 1.At rest, cells use up to 40% of their energy for this process. 2.Carried out by membrane proteins

Molecule to be carried Molecule being carried Energy  DRAW FIG 7-19, pg. 189

Active Transport Movie

B.Endocytosis - surrounding a substance with some of the cell membrane then bringing it into the cell within a vacuole. 1.Phagocytosis - Solids 2.Pinocytosis- Liquids C.Exocytosis – opposite of endocytosis.  DRAW

Endo/Exocytosis Movie