Cell Membrane

•Also known as the Plasma Membrane

•Surrounds the cell

•Semi-permeable

•Selectively permeable –”chooses” what enters and leaves

•MOST OF TIME BASED ON SIZE OF MOLECULE

•Made of a bilayer (2) of lipids AND proteins

Concentration

Gradient

Difference in concentration between the 2 areas

Cells transport materials by the following processes

1. PASSIVE TRANSPORT

When particles move from an area of high concentration to an area of low concentration

Molecules Move with the gradient

no energy needed

2. ACTIVE TRANSPORT

When particles move from an area of low concentration to an area of high concentration

Molecules Move against the gradient

energy required

HIGH LOW

Passive Transport

2 Types

1. Diffusion2. Osmosis

•No energy •High low

Diffusion Substances other than water that move from HIGH LOW

HIGH

LOW

DIFFUSION

Equilibrium is reached

Molecules eventually stop moving when…..

no further change in conc. occurs & both sides are equal

Diffusion through a membrane

Cell membrane

Inside cell

Outside cell

Cell membrane

Inside cell

Outside cell

diffusion

Diffusion through a membrane

Cell membrane

Inside cell

Outside cell

EQUILIBRIUM

Diffusion through a membrane

Do Now: Identify this process by name and explain why you

chose that process.

Osmosis

•DIFFUSION OF WATER INTO AND OUT OF THE CELL

•Movement of WATER from HIGH LOW Concentration

•With the Conc. Gradient•NO ENERGY NEEDED!

Inside cell Outside cell

OsmosisCell membrane

High conc. of water molecules.

Low conc. of water molecules.

Inside cell Outside cell

High conc. of water molecules.

OsmosisCell membrane

OSMOSIS

Low conc. of water molecules.

OsmosisCell membrane

Inside cell Outside cell

OSMOSIS

EQUILIBRIUM. Equal water concentration on each side.

Whathappenswhen you

place acell in:

•1. Salt water: •CELL SHRINKS bc osmosis occurs water moves out of cell

Red blood cells that were placed in a salt solution

**Plant cells don’t shrink b/c of rigid cell wall cell membrane pulls away from cell wall**

Onion Skin Cells

•2. Distilled/ pure water•Cell fills up with water bc water moves into cell due to osmosis

•Animal cells = •swell & burst

•Plant cells = •swell, but do not burst b/c of their cell wall

Red blood cell in distilled water about to burst

Animal Cells

Same amount of

water inside and outside

the cell

Distilled water Salt solution

Plant Cells

Same amount of water

inside and outside the

cell

Distilled water Salt solution

DO NOW:In your own words describe the similarities and differences of diffusion and osmosis.

The similarities ofdiffusion andosmosis are

_____________________________The differences ofdiffusion andosmosis are ____________________________________

TOPIC: CELLSAIM: HOW DOES ACTIVE TRANSPORT

OCCUR?

ActiveTransport

• Movement of molecules from an area of low concentration to an area of high concentration

• Against the Conc. Gradient

• ENERGY IS NEEDED!

L

H

L

H

LOW

(energy)

PROTEIN

CELL MEMBRANE

Active Transport (animation).mov

What process is each cell carrying out?

Active Transport

Passive Transport

Endocytosis

Taking substances into cell by surrounding it with the cell membrane

How some uni-cellular organisms take in food

Form of ACTIVE TRANSPORT (energy required)

Cell membrane folds in causing a vesicle to form

Exocytosis

Vesicle fuses with cell membrane causing the

materials inside to be released

Also a form of Active Transport