7-3 Cell boundaries

1. 7-3 Cell boundaries

2. Cell membrane • Define: The cell membrane regulates what enters and leaves the cell and also provides protection and support. • Composition: Made up of a double-layered sheet called a lipid bilayer • The lipid bilayer gives the cell membrane a flexible structure that forms a strong barrier between the cell and its surroundings. • The lipid bilayer also includes proteins used to channel molecules across and carbohydrates for communication.

4. Cell Wall • The main function of the cell wall is to provide support and protection for the cell • Plant cell walls are made up of cellulose

5. Quick Review • Solution – A mixture of two or more substance • Solvent – The liquid in which a solute is dissolved to form a solution • Solute – The substance dissolved in the solution • Concentration – The mass of a solute found in a volume of solution. Mass / Volume (g/L)

6. Transport Active Passive • Transport across a membrane that requires the cell to use NO energy • Transport across a membrane that requires the cell to use energy

7. Diffusion • Diffusion is the process of particles moving from an area of high concentration to an area with low concentration • When the concentration of the solute is the same throughout a system, the system has reached equilibrium • Because diffusion depends upon random particle movement, substances diffuse across membranes without requiring the cell to use energy

8. Diffusion • Diffusion does not require energy!

9. FAcilitated diffusion • Few molecules are too big to get through the membrane by themselves. • Facilitated: Make an action or process easier. • Facilitated diffusion: Molecules that cannot normally pass through the cell membrane get help using their own personnel protein channel. • NO ENERGY REQUIRED!!!

10. Active Transport • Uses energy • Generally carried out by transport proteins or “pumps” • “Pumps” work pumping concentration from low to high. (Backwards from normal)

11. Osmosis • Most biological membranes are selectively permeable. Only allowing some substances through and denying others. • Osmosis is the diffusion of water across a selectively permeable membrane.

12. How osmosis works • Movement of WATERfrom an area of high concentration to an area with low concentration. • Water will continue to move across a membrane until equilibrium is complete. • Isotonic – Same strength of solute • Hypertonic – Above strength of solute • Hypotonic – Below Strength of solute

13. Osmotic Pressure • For cells to survive, they must find a way to balance the intake and outtake of water. • If balance is not met, a force called osmotic pressure occurs. Creating a situation where cells will struggle to survive.

15. Endocytosis • Process of taking material into the cell by means of infolding or pockets. • Pocket breaks loose and forms a vacuole. • Two main types of endocytosis • Phagocytosis • Pinocytosis

16. Phagocytosis • “Cell Eating” • Cell slowly surrounds and engulfs the food.

17. Pinocytosis • “Cell Drinking” • Cells form tiny pockets around the cell wall and fill them with liquid and pinch off

18. Exocytosis • Removal from the cell • Vacuole fuses with the cell membrane, forcing the contents out of the cell • Contractile vacuole in some fresh water protists.