7-3 Cell Boundaries YOU WILL LEARN: What are the main functions of the cell membrane and the cell wall? What is Passive Transport? –Diffusion, osmosis and Facilitated Diffusion What is Active Transport? –Endocytosis & Exocytosis

Cell Membrane- controls what enters and leaves the cell and also provides protection and support. –Nearly all cell membranes are made of a lipid bilayer –Lipid bilayer gives cell membranes a flexible structure that forms a strong barrier between the cell and its surroundings

Cell Membrane Look on page 182 figure 7-12 Lipid Bilayer Phospholipid

Cell Wall- provides extra support and protection for the cell Found in plants, fungi, algae and many prokaryotes. Plants cell walls are made mostly of cellulose, a tough carbohydrate fiber What common item is made of cellulose???

Cell Wall

Types of Cellular Transport Passive Transport cell doesn’t use energy 1.Diffusion 2.Facilitated Diffusion 3.Osmosis Active Transport cell does use energy 1.Protein Pumps 2.Endocytosis 3.Exocytosis high low This is gonna be hard work!! high low Weeee!!! Animations of Active Transport & Passive TransportAnimations

Diffusion Through Cell Boundaries Concentration- mass of a solute in a given volume of solution (mass/volume) –Example- If you have 12 grams of salt in 3 L of water what is the concentration? (12g/3L = 4g/L) grams per liter

Diffusion- process by which molecules tend to move from an area of high concentration to an area of low concentration Equilibrium- when the concentration of a solute is the same throughout the solution Diffusion does NOT require ENERGY!!!

Diffusion Look on page 184 Figure 7-14

Osmosis Osmosis-diffusion of water through a selectively permeable membrane

Osmosis – the diffusion of water! Water moves freely through pores. Solute (green) too large to move across.

Isotonic-when the concentration of two solutions is the same Hypertonic-when comparing two solutions, the solution with the greater concentration of solute Hypotonic- when comparing two solutions, the solution with the lesser concentration of solute

What happens to cells that take on additional water? _________________ What happens to cells that lose water? ___________________________

What type of solution are these cells in ? A CB HypertonicIsotonicHypotonic

Osmotic Pressure Osmosis exerts a pressure on hypertonic side of permeable membrane (Osmotic Pressure) Osmotic Pressure may cause problems for the cell---cell may burst

Facilitated Diffusion Look on page 187 Figure 7-17 Movement of specific molecules across cell membranes through protein channels Movement is still from high concentration to low concentration Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)

Active Transport Movement of materials across a cell membrane AGAINST a concentration of difference (from LOW to HIGH concentration) Requires ENERGY Examples: Endocytosis, exocytosis

ENDOCYTOSIS process of taking material into a cell by means of infoldings, or pockets, of the cell membrane Allows larger molecules and even solid clumps of material to be transported Phagocytosis (cell “eating”) and pinocytosis (cell “drinking”)

Phagocytosis- “ cell eating ” extensions of cytoplasm surround a particle and package it within the food vacuole. The cell then engulfs it

Pinocytosis- ( “ cell drinking ” ) process by which a cell takes in liquid from the surrounding environment Tiny pockets form along cell membrane, fill with liquid, and pinch off to form vacuoles

Exocytosis- process by which a cell releases large amounts of material Membrane of vacuole surrounding the material fuses with the cell membrane, forcing contents out of cell –Contractile vacuole