In your notebook…. Describe a mosaic, and then compare a cell membrane to it

Two major components: Phospholipids Proteins

Fluid Mosaic Model emb.htmhttp:// emb.htm iUj80http:// iUj80

Roles of the membrane proteins Move stuff across the membrane that can’t get across on its own Recognition – like nametags Receptors – trigger cellular responses Enzymes

It’s also called a lipid bi-layer

HYDROPHILIC HYDROPHOBIC

Back to your homework… What kinds of molecules can cross the cell membrane, according to the diagram?

Examples of small polar and nonpolar substances: O 2 CO 2 H 2 O

Homework diagram… How do they cross? In which direction do they cross?

Make some predictions about your lab… What do you think will happen to the mass of your cell? Why? Which way do you think substances will move? Why?

Compare your data with others. You need to collect results from all three situations.

Claim 1: Substances will diffuse across a permeable membrane. Evidence: Rationale/Reasoning:

Claim 2: The cell membrane is selectively permeable. Evidence: Reasoning/Rationale:

Role of the membrane? Selective permeability

Cell Membrane Cell Membrane Animation Made of phospholipids and proteins Molecules move into and out of a cell through the cell membrane The cell membrane is selectively permeable How certain molecules move through the cell is called cell transport –Passive Transport –Active Transport

Questions What happens when you spray air freshener or perfume? What happens when you put food coloring in water? THIS IS DIFFUSION!!!! Diffusion is also one way things are transported across the cell membrane

What is concentration? Amount of solute in a certain amount of solvent…think about kool-aid… –Solvent – what does the dissolving (liquid) –Solute – what is dissolved in the solvent –Which is more concentrated?

Diffusion Dynamic Equilibrium

Make a hypothesis…. Will the glucose move? Which way? Why or why not? Will the iodine move? Which way? Why or why not? Will the starch move? Which way? Why or why not?

For lab… To the tube, add: –Glucose solution –Starch To the beaker, add: –Water –Iodine

Flea Diffusion Analogy

Dynamic Equilibrium

Selectively permeable DefinitionIllustrate Explain your illustration What qualities might affect how easily a molecule can move through a membrane?

Sizes of Molecules… Water (H 2 O) Iodine (I 2 K) Glucose (C 6 H 12 O 6 ) Food Coloring (~450 atoms) Starch (~1000 atoms) So…how big are the pores of the membrane? Make an estimate

How does the membrane regulate movement of molecules? It’s structure dictates!!

Two major components: Phospholipids Proteins

HYDROPHILIC HYDROPHOBIC

Examples of small polar and nonpolar substances: O 2 CO 2 H 2 O

Flea Diffusion Analogy

Dynamic Equilibrium

The fish can still move…so we call this DYNAMIC EQUILIBRIUM

Lipid bi-layer Fluid mosaic model – kuIhttp:// kuI – pghttp:// pg

Passive Transport Particles move from high concentration to low concentration Does NOT require extra cell energy Includes simple diffusion, osmosis, facilitated diffusion

SIMPLE DIFFUSION Movement of molecules from areas of high concentration to areas of low concentration Does not require energy (PASSIVE) –Because molecules are in constant, random, motion! Will diffuse until reaches equilibrium (equal concentrations) Dynamic equilibrium (still moving!)

Simple Diffusion in Cells Diffusion Animation Diffusion Across a Membrane hill.com/sites/ /student_view0/c hapter38/diffusion_through_cell_membrane s.html

What kinds of things diffuse through the membrane? SMALL AND UNCHARGED –Like carbon dioxide and oxygen.

OSMOSIS The diffusion of water across a membrane from an area of high concentration to low concentration No energy required (PASSIVE TRANSPORT) Occurs until reaches DYNAMIC EQUILIBRIUM –Equal concentrations on both sides of the membrane

Tonicity of solutions Used to compare the relative concentrations Hypertonic –solution with a higher concentration of solute –So lower water concentration Hypotonic –solution with a lower concentration of solute –So higher water concentration Isotonic –solutions with equal concentrations of solute Water diffuses from hypotonic solutions to hypertonic solutions!

Cells in Hypertonic Solution Water moves out of the cell Cell shrivels HYPERTONIC Hi Low

Hypotonic Solution Water moves into the cell Cell swells –Animal cell – can burst –Plant cell – builds up pressure on cell wall, but rigid cell wall keeps it from bursting HYPOTONIC Hi Lo

Isotonic Solution Water moves in and out of the cell Cell stays the same size Dynamic Equilibrium ISOTONIC

PROBLEM BREAK

i3a1/Cells/Osmosis.htm

What happens to slugs in salt? Dead bodies in the river?

Pumping Water Some organisms have vacuoles that pump out excess water that enters the cell Too much water in the cell = vacuole works hard pumping out water! transport.htm#Brownian_Movementhttp:// transport.htm#Brownian_Movement

FACILITATED DIFFUSION

Particles move from high concentration to low concentration No energy needed (PASSIVE) Cells use proteins to “help” –Transport Proteins –Channel proteins

FRAYER MODEL BREAK! Passive Transport define Draw example Explain your example Name two examples of things that can cross the membrane passively

REVIEW PASSIVE TRANSPORT

Active Transport Particles move from low concentration to high concentration (against the concentration gradient) DOES REQUIRE ENERGY!! Requires transport proteins Includes pumps, endocytosis, exocytosis, etc.

The sodium-potassium pump Active Transport = requires energy! Sodium is pumped out Potassium is pumped in Animation

Active transport  Examples: Pumping Na + (sodium ions) out and K + (potassium ions) in against strong concentration gradients.  Called Na+-K+ Pump

Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential

Pumps Some animals use salt pumps to maintain a constant concentration of salt in their bodies This requires energy! ACTIVE TRANSPORT!

Large substances enter the cell Cell membrane forms a “pit” and wraps around substance Cell membrane pinches off – forms a vesicle

Large substances leave the cell Vesicle fuses with cell membrane and dumps contents

Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment

FRAYER MODEL BREAK! Active transport define Draw example Explain your example Does it require energy? Examples

ACTIVE TRANSPORT PASSIVE TRANSPORT VENN DIAGRAM TIME: MUWAHAHAHAHA

Pom-Pom Potential Modeling passive and active transport along a cell membrane in a NERVE CELL What do nerves do? How do they do it?

Questions How did this activity model passive transport? How did this activity model active transport? Why do the membranes “work” to keep the charges on either side of the membrane “balanced”?

MOVING THE BIG STUFF…

Moving the “Big Stuff” Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. Exocytosis Exocytosis - moving things out. This is how many hormones are secreted and how nerve cells communicate with one another This is how many hormones are secreted and how nerve cells communicate with one another.

Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.

Ponder for a moment… How does exocytosis fit into PROTEIN SYNTHESIS????

Cell Signaling Signaling activity Modeling Nerves…

Go to picture

Journal Draw a diagram of what we just did and… Identify the types of transport going on, as completely as possible (there are TWO you should identify!). Provide justification for your selection.