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 cellEQUILIBRIUM
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
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