Unit 4: The Cell & Its Environment Ch. 2:1 (pg. 31) Cell Theory Ch. 2:3 (pgs ) Special Cell Processes (Diffusion & Osmosis)

Cells Who first observed cells? –Robert Hooke What was he looking at? –cork Did he see live cells? –No, just cell walls. Robert Hooke cork

Further Discoveries Lead to the Cell Theory 1.All organisms are made of one or more cells. 2.The cell is the basic unit of structure and function in organisms. 3.All cells come from other cells. Cell Theory Rap

Properties of the Plasma Membrane What are the functions (jobs) of the cell membrane? 1.boundary between cell & its environment 2.“gatekeeper” (Only l ets certain materials in/out.) “selectively permeable”

A Model of the Plasma Membrane In general, what does the plasma (cell) membrane look like? –phospholipid bilayer

What does the plasma (cell) membrane look like in more detail? –“Fluid Mosaic Model” Molecules (like proteins) embedded in phospholipid bilayer & in constant motion A Model of the Plasma Membrane Membrane Movement Animation

What is passive transport? –movement of molecules from an area of high concentration to low concentration (with the gradient) Does passive transport require energy? Why/why not? –No, b/c going w/ gradient –Ex. of passive transport? diffusion, osmosis, facilitated diffusion Movement of Materials Across the Cell Membrane: Passive Transport concentration gradient = differences in concentration

Ex. Diffusion –How do molecules of a solute (dissolved substance) move? From high to low concentration –Do they ever completely stop? No, “dynamic equilibrium” is reached (= in/out movement) Movement of Materials Across the Cell Membrane: Passive Transport

What is the special name for the diffusion of water? –osmosis Movement of Materials Across the Cell Membrane: Passive Transport

What is an isotonic solution? –concentration of solutes (& water) same on both sides of the membrane Which way would water move? –In & out equally “no net movement” Effects of Water Concentrations on Cells How osmosis works animation

What is a hypotonic solution? –lower concentration of solutes outside cell higher concentration of water outside cell Which way would water move? –into the cell Effects of Water Concentrations on Cells How osmosis works animation

What is a hypertonic solution? –higher concentration of solutes outside cell lower concentration of water outside cell Which way would water move? –out of the cell Effects of Water Concentrations on Cells How osmosis works animation

plasmolysis cytolysis What adaptation prevents the plant cell from bursting? What happens to cells in different types of solutions? Effects of Water Concentrations on Cells: Cytolysis & Plasmolysis cell wall

Which cells were in salt water? How can you tell? Elodea in hypertonic solution Elodea in isotonic solution Blood in isotonic solution Blood in hypertonic solution Blood in hypotonic solution

Even though they’re going w/ the concentration gradient (high  low) some substances: –can not dissolve in lipid bilayer –are too large to squeeze through Membrane Function Passive Transport: Facilitated Diffusion carrier

So how can these materials permeate the membrane??? –facilitated diffusion with the help of: –channel proteins (pores) –carrier proteins –gate proteins –Does facilitated diffusion require energy? Why/why not? No, b/c going from high  low concentration Membrane Function Passive Transport: Facilitated Diffusion carrier

Channel & Gate Protein Animations carrier (transport) protein channel protein (pores) Gate opens & ions can pass through Signal molecule combines w/ gate Signal molecule not combined w/ gate (gate closed) Once ions pass through, signal molecules unbind & gate closes gat e protein

What is active transport? –Movement of molecules from an area of low to high concentration (against the gradient) Does active transport require energy?Why/why not? –Yes, b/c going against gradient –Ex. of active transport? many ions (ex. sodium ion) Movement of Materials Across the Cell Membrane: Active Transport concentration gradient = differences in concentration

How can materials be moved against the concentration gradient (low  high)? –transport proteins (pumps) that use energy (ATP) Movement of Materials Across the Cell Membrane: Active Transport Protein/Transport Pumps Animation Active Transport Animation Passive & Active Transport Animation

Not all materials can pass through membrane… –So, how do they get into/out of the cell? membrane encloses the material  pinches off  releases the material on the other side –endocytosis (enter cell) –exocytosis (exit of cell) Exocytosis & Endocytosis Animation 1Endocytosis & Exocytosis Animations 2 Active Transport: Endocytosis & Exocytosis

Which way do substances move during endocytosis? –enter cell What are 2 types of endocytosis? –phagocytosis (for large particles)phagocytosis –pinocytosis (for liquids) –Do they require energy? Why/why not? Yes, b/c against gradient Exocytosis & Endocytosis Animation 1 Endocytosis & Exocytosis Animations 2 Liquid droplets Active Transport: Endocytosis & Exocytosis

Which way do substances move during exocytosis?exocytosis –exit the cell What types of materials are moved by exocytosis? –ex. wastes, hormones –Does exocytosis require energy? Why/why not? Yes, b/c against gradient Exocytosis & Endocytosis Animation 1 Endocytosis & Exocytosis Animations 2 Active Transport: Endocytosis & Exocytosis

The Cell Wall What is the cell wall? –the rigid, outermost boundary of many cells (outside the cell membrane) What types of organisms have cell walls? –plants, fungi, bacteria, most algae

The Cell Wall What are cell walls made of? –in plants: cellulose (a carbohydrate) What does the cell wall do for the cell? –provides protection & support Do cell walls affect a cell’s permeability? –NO, spaces between fibers allow water, ions, & other particles to pass through