Cell (Plasma) MembraneWhat is it made of?

Why is this a good material for a cell membrane?

Cell Membrane

• Phospholipid bilayer• Hydrophilic head• Hydrophobic tail

Cell Membrane

• Homeostasis – Steady state maintained by

the body • Selectively Permeable

– Regulates what can come in and out of the cell

Selectively Permeable (6.3) CANSmall Nonpolar

– (O2)

– (CO2) – WATER

CANNOT – Large (glucose)– Polar ( exception is water because its so

small) – Ion (charged)

Breathing

Proteins in the Cell Membrane

• “Fluid Mosaic Model” – Many proteins will help

transport molecules across the membrane

– Proteins drift freely

Membrane Proteins Embedded

1. Transport Proteins2. Cell Recognition

Proteins- sugars hang off proteins

3. Receptors Proteins- receive signals

4. Enzymes- proteins that make reactions happen

Cell Recognition Proteins

• Sugars hang off of proteins in the cell membrane

• Give us different blood types

Receptor Protein

Receptor Protein- is a cell membrane protein that receives a signal

Transport

Passive Transport: Diffusion

• Diffusion • The movement of

particles HIGH concentration to LOW concentration

Why? • Molecules are always in

random motion

Ex. Perfume, food coloring, tea bag

Equilibrium- particles equally spread out

Osmosis Water ONLY!- Diffusion of water from HIGH to LOW

concentrationSolute: Substance in solution that is dissolved (ex. Sugar or Salt)

Solvent: Substance in solution that does the dissolving ( ex. Water)

Hypotonic Environment

Hypertonic Environment

Isotonic Environment

TONICITY

Isotonic

97% H2O

Diagram

Where is the most water?

Which way does water go?

Result?

Big words

Examples

97% H2O

Same

Inside and outside

Even, same concentration overall

“dynamic equilibrium” “homeostasis

contact lens solution, Gatorade

97% H20

HypotonicDiagram

Where is the most water?

Which way does water go?

Result?

Big words

Examples

97% H2O

Outside

Inside

Burst, get bigger; firm

“cytolysis”- to burst; “turgid”- get firm; “turgor pressure” :pressure inside plant cells to help stand upright

- Distilled water ( 100% Water) - Plants standing upright

92 % H20

mailto:http://www.youtube.com/watch?v=EA_ss8ZkjAM

HypertonicDiagram

Where is the most water?

Which way does water go?

Result?

Big words

Examples

80% Water

Inside

Outside

Smaller, shrink, go limp

“plasmolysis”- to wilt, shrivel, loss of pressure; “flaccid”- go limp

97% H20

Hypertonic Red Blood Cells

Check Yourself

Is the lettuce in a hypertonic isotonic hypotonic environment and why??

Poll

Passive Transport: Facilitated Diffusion

Facilitated Diffusion- diffusion across a

membrane through transport proteins

Ex. sugars, ions , alcohol

NO ENERGY: From HIGH to LOW concentration

Active Transport Movement of molecules across a membrane require energy• From LOW to HIGH concentrations!

Why? • To maintain a certain internal environment: • 1. Sodium Potassium Pump

Active Transport

Exocytosis & Endocytosis

1. Exocytosis - Removal of materials - Vesicle fuses with

membrane, forcing contents out

Active Transport 2. Endocytosis• process of taking in

materials by infolding of the cell membrane

• Pocket breaks and forms a vesicle in the cell • Ex.

• Pinocytosis: take in fluid

• Phagocytosis: Large particle/food• Amoeba

Concentration Gradient measurement of how the concentration of something changes from one place to another

B. Passive Transport: molecules go DOWN concentration gradient

from HIGH to LOW concentration

C. Active Transport: molecule go UP concentration gradient from

LOW to HIGH concentration

• Review Video of Transport

Elodea Plasmolysis

http://www.youtube.com/watch?v=2Th0PuORsWY

“Egg”citing “Eggs”periment Cell membrane

Egg Lab: Osmosis

Why does a plant like hypotonic but an animal does not?

• http://www.phschool.com/science/biology_place/labbench/lab1/watpot.html