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The “bouncer” of the cell The Cell Membrane The “bouncer” of the cell

The Cell Membrane – (Plasma Membrane) The barrier of the Cell

Functions (Jobs) of The Cell Membrane Separates cell from outside environment Protective barrier Regulates movement in & out of cell Ex. Windows Screen in spring

Selectively Permeable Membrane Selectively permeable: Only certain molecules can pass through Small molecules move through easily Ex: O2, CO2, H2O

Selectively Permeable Membrane Large molecules can NOT move through Ex: starch SIMPLE SUGARS STARCH

Transport: movement of materials across the membrane Three types of transport: Constant, free movement of small molecules ( glucose, O2, CO2 ) Free movement of water Movement that requires energy (ATP): things that are forced through membrane

What happens when you spray air freshener? 11/30/08 What happens when you spray air freshener?

11/30/08 First type: Diffusion Diffusion: Molecules move freely from where there’s the most, to where there’s the least of them

Passive: doesn’t require energy, happens freely 11/30/08 Diffusion is passive Passive: doesn’t require energy, happens freely 10

11/30/08 Diffusion of Liquids 11

Which way will the glucose move? 11/30/08 Which way will the glucose move? Equilibrium Molecules will move until there’s an equal amount on both sides- called equilibrium 12

Concentration: how densely packed something is 11/30/08 Concentration: how densely packed something is Example Low concentration: loosely packed High concentration: tightly packed

Concentration: how tightly packed the molecules are 11/30/08 Concentration: how tightly packed the molecules are Example Low concentration: a little sugar dissolved High concentration: a LOT of sugar dissolved

Which side is high concentration? 11/30/08 Which side is high concentration? High Concentration Low Concentration A) B) A) More tightly packed

Diffusion across a membrane Semipermeable membrane 11/30/08 What is Osmosis? Diffusion across a membrane Diffusion of water across a membrane Moves from HIGH water concentration to LOW water concentration Semipermeable membrane 16

Diffusion of H2O Across A Membrane 11/30/08 Diffusion of H2O Across A Membrane High H2O concentration Low H2O concentration Which way will water move? When is equilibrium reached?

Where will water move? CELL 10 Glucose 90 H2O IN to the CELL 11/30/08 Where will water move? 10 Glucose 90 H2O IN to the CELL CELL 20 Glucose 80 H2O

Where will water move? CELL 90 Glucose 10 H2O Out of the CELL 11/30/08 Where will water move? 90 Glucose 10 H2O CELL Out of the CELL 80 Glucose 20 H2O

Where will water move? CELL 10 Glucose 90 H2O 10 GLucose 90 H2O 11/30/08 Where will water move? CELL 10 Glucose 90 H2O 10 GLucose 90 H2O The water is already balanced! equilibrium The cell is at _______________.

What happens when you pour salt on a slug??  The slug’s cells dehydrate and this kills the slug

Why does popcorn make us thirsty?? Mouth Cell WATER Huge popcorn =A big scam Makes you super thirsty! SALT

More Water outside, water moves in More water inside, water moves out 11/30/08 Dots = salt More Water outside, water moves in More water inside, water moves out Equal amount of water NO NET MOVEMENT OF H2O (equal amounts entering & leaving) (Cell Swells) (shrinking of a cell) Water moves towards where the most dots are 23

Osmosis in Red Blood Cells 11/30/08 Osmosis in Red Blood Cells Which way did the water move? 24

Which way did the water move? 11/30/08 25

Transport helps to maintain Homeostasis Homeostasis: A balanced, steady state Does this by controlling what enters & leaves the cell

Last type of transport: Active transport Molecules move from where there’s the least to where there’s the most (the opposite of diffusion) Requires ATP!

Diffusion vs. Active Transport -High to Low concentration -Low to High concentration -Uses ATP

11/30/08 Exit card... Many poisons work by inhibiting ATP production. Which type of transport would be most affected? a. osmosis b. diffusion c. active transport

Is diffusion an active or passive process? Does it use energy? 11/30/08 Lets Review… Define Diffusion Is diffusion an active or passive process? Does it use energy? How is active transport different from passive transport? True or False: Osmosis is a type of diffusion 30

Describe what is happening: 11/30/08 Describe what is happening: