At the end of this unit At the end of this unit you should be able to you should be able to explain why the following explain why the following occurs…occurs…

http://www.youtube.com/watch?v=H6N1IiJTmnc

Questions of the Questions of the day…day…

What keeps cells from exploding?What keeps cells from exploding?

Why do they “mist” or spray water at the grocery Why do they “mist” or spray water at the grocery store?store?

How does your body get the nutrients it needs in How does your body get the nutrients it needs in and the waste nutrients out of each cell?and the waste nutrients out of each cell?

Which cells have Cell Which cells have Cell Membranes?Membranes?

Cell Membranes vs. Cell WallsCell Membranes vs. Cell Walls Cell Membranes Cell Membranes

regulate what regulate what

comes into and comes into and

out of cellsout of cells Cell Walls Cell Walls

provide provide

protection and protection and

support for support for

the cellthe cell

Electron micrograph of Electron micrograph of cell membranecell membrane

Phospholipids make up Phospholipids make up cell membranescell membranes

Polar “head” that is attracted to water

Non-polar “tails” that are not attracted to water but are attracted to other phospholipid tails

Phospholipids make up cell Phospholipids make up cell membranesmembranes

Water molecules

Water

Polar head faces out towards water because of the attraction

Nonpolar tails face inward so they are protected from water

Membranes are picky!!!Membranes are picky!!!

Membranes are Membranes are semi-permeablesemi-permeable because because they only let certain molecules throughthey only let certain molecules through

Small and non-polar molecules can pass Small and non-polar molecules can pass through easily through easily

Large and polar molecules cannot pass Large and polar molecules cannot pass through without help through without help

http://www.youtube.com/watch?v=6Rd2bEp380w

Both water and nutrients Both water and nutrients can move in and out of can move in and out of cells.cells.

Diffusion discusses the Diffusion discusses the movement of particlesmovement of particles

Diffusion-Diffusion- The movement of particles from a The movement of particles from a region of higher concentration to a region of region of higher concentration to a region of lower concentration, caused by the random lower concentration, caused by the random motion of particles.motion of particles.

Ex: Body SprayEx: Body Spray

Food Coloring/WaterFood Coloring/Water

Osmosis-Osmosis- The diffusion of The diffusion of waterwater across across a semi-permeable membrane towards a semi-permeable membrane towards the side with higher solute concentration.the side with higher solute concentration.

Draw a picture where Draw a picture where molecules would diffuse molecules would diffuse out of a membraneout of a membrane

Draw a picture where Draw a picture where molecules would diffuse molecules would diffuse into a membraneinto a membrane

Osmosis discusses water Osmosis discusses water movement:movement:

If there is more water outside(less If there is more water outside(less particles)…particles)… Water will move into the cell Water will move into the cell

If there is more water inside (more If there is more water inside (more particles)particles) Water will move out of the cellWater will move out of the cell

Draw a picture where Draw a picture where water would move into water would move into the cellthe cell

Draw a picture where Draw a picture where water would move out of water would move out of a cella cell

Visual ExamplesVisual Examples

Water will move into cell

Water will move out of cell.

Water will stay put.

Where will particles Where will particles diffuse?diffuse?

Lets set up a LabLets set up a Lab

Purpose: To determine if glucose and Purpose: To determine if glucose and starch are permeable through a model starch are permeable through a model cell membrane.cell membrane.

Hypothesis: Hypothesis:

GlucoseGlucose

bonds have some areas of charge bonds have some areas of charge (somewhat polar)(somewhat polar)

http://www.3dchem.com/molecules.asp?ID=423#http://www.3dchem.com/molecules.asp?ID=423#

StarchStarch

Few areas of Charged bondsFew areas of Charged bonds

PicturePicture

How could we check for How could we check for the presence of starch?the presence of starch?

Starch turns black in the presence of Starch turns black in the presence of IodineIodine

How could we check for How could we check for the presence of sugar?the presence of sugar?

Glucose test strips tell presence of sugarGlucose test strips tell presence of sugar

How could we set up an How could we set up an experiment to see if experiment to see if starch and sugar will starch and sugar will move through a move through a membrane?membrane?

Procedure:Procedure:

MATERIALSMATERIALS

3-150 mL beaker3-150 mL beaker 1-10 mL graduated cylinder1-10 mL graduated cylinder 10% IKI solution10% IKI solution 2 Glucose Test Strips2 Glucose Test Strips 2 pieces of string (10-20 cm)2 pieces of string (10-20 cm)

Materials ContinuedMaterials Continued

1-20 cm piece of dialysis tubing1-20 cm piece of dialysis tubing 1-100 mL graduated cylinder1-100 mL graduated cylinder 1-Scissors1-Scissors Starch/Glucose SolutionStarch/Glucose Solution

1. Record color of Initial Solutions1. Record color of Initial Solutions 2. Record Glucose presence of 2. Record Glucose presence of

Starch/Glucose Solution (Done by Miss Starch/Glucose Solution (Done by Miss H)H)

3.Obtain one piece of Moist Dialysis 3.Obtain one piece of Moist Dialysis tubingtubing

4. Seal one end of the tube by folding the 4. Seal one end of the tube by folding the end over and tying with thread to form an end over and tying with thread to form an open bagopen bag

5. Obtain 10 mL of Starch/Glucose 5. Obtain 10 mL of Starch/Glucose Solution in your graduated cylinderSolution in your graduated cylinder

Fill your bag with Starch/Glucose solution Fill your bag with Starch/Glucose solution (about 10 mL)(about 10 mL)

Leave about 2 cm of room at the top of Leave about 2 cm of room at the top of bag.bag.

Squeeze excess air of of bagSqueeze excess air of of bag Place your bag in the 150 mL beaker and Place your bag in the 150 mL beaker and

completely cover with 10% Iodine Solutioncompletely cover with 10% Iodine Solution

Procedure Continued..Procedure Continued..

Tie up bag as shown by Miss HTie up bag as shown by Miss H Wait 10 minutes and remove your cell from Wait 10 minutes and remove your cell from

the iodine.the iodine. Use scissors to empty contents of your cell Use scissors to empty contents of your cell

into a clean beakerinto a clean beaker Observe color and contents of the cell Observe color and contents of the cell Test contents for glucoseTest contents for glucose Test the iodine solution for glucoseTest the iodine solution for glucose

What Data should we What Data should we take?take?

Observations inside and Observations inside and outside of cell membraneoutside of cell membrane

Initial Cell Contents

Initial Beaker Final Cell Contents

Final Beaker

Color

Glucose Test Strip