Cell MembraneI. HOMEOSTASIS: internal “steady state” maintained by the body1. What is the cell membrane made of?

– Phospholipid bilayer• Hydrophobic tails• Hydrophilic head

II. Cell Membrane

• Homeostasis – Steady state maintained by

the body

• Selectively Permeable – Regulates what can come in

and out of the cell

1. Selectively PermeableCAN EASILY PASS:Small, Nonpolar

– O2

– CO2

– Water (only through protein channels)

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

small) – Ion (charged)

Breathing

III. Proteins in the Cell Membrane

• “Fluid Mosaic Model” – Many proteins will help the

membrane

– Proteins drift freely

Membrane Proteins Embedded

1. Transport Proteins

2. 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

1. Passive Transport: Diffusion • The movement of particles

HIGH concentration to LOW

concentration

Why? • Molecules are always in

random motion – Ex. Perfume Food coloring Tea bag

b) Equilibrium- particles equally spread out

2. Passive Transport: Osmosis- Diffusion of water from HIGH to LOW

concentration Solute: 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

Candy, sugar, salt on bushes/grass, gargle with salt water

Hypertonic Red Blood Cells

Check Yourself

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

Poll

Passive Transport: 3. Facilitated Diffusion

Facilitated Diffusion- diffusion across a

membrane through transport proteins

a) Ex. sugars, ions , alcohol b) NO ENERGY: From HIGH to LOW concentration

V. Active Transport • Movement of molecules across a membrane require

energy• From LOW to HIGH concentrations!

a) Why? • To maintain a certain internal environment• To transport large molecules in/out

H2OH2O

H2OH2O

H2OH2O

The water from soil moves into roots from HIGH to LOW. But then eventually, the roots will have more water. To prevent the water from going back out, the tree uses ACTIVE TRANSPORT to keep pumping more water in.

Active Transport C) Some Types of Active Transport

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, forming a vesicle

• Ex.• Phagocytosis: Large

particle/food• Amoeba

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

Passive Transport: molecules go DOWN concentration gradient from HIGH to LOW concentration

Active Transport: molecule go UP concentration gradient from LOW to HIGH concentration

Example of DOWN concentration gradient:

Students going from classrooms into hallways for next class

Example of UP concentration gradient:

At a concert, moving into the crowd towards crowded stage

• Review Video of Transport

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

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

Elodea Plasmolysis

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

“Egg”citing “Eggs”periment Cell membrane

Egg Lab: Osmosis