Topic: Cells Aim: How does the cell mebrane work?

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. Diffusion 2. Osmosis

No energy High  low

Substances other than water that move from HIGH  LOW Diffusion

DIFFUSION LOW HIGH

Molecules eventually stop moving when….. Equilibrium is reached no further change in conc. occurs & both sides are equal

Diffusion through a membrane Cell membrane Outside cell Inside cell

Diffusion through a membrane Cell membrane diffusion Outside cell Inside cell

Diffusion through a membrane Cell membrane Outside cell Inside cell EQUILIBRIUM

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!

Osmosis Cell membrane Outside cell Inside cell High conc. of water molecules. Low conc. of water molecules.

Osmosis OSMOSIS Cell membrane Outside cell Inside cell High conc. of water molecules. Low conc. of water molecules.

Osmosis OSMOSIS EQUILIBRIUM. Equal water concentration on each side. Cell membrane OSMOSIS Outside cell Inside cell EQUILIBRIUM. Equal water concentration on each side.

What happens when you place a cell 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

Same amount of water inside and outside the cell Animal Cells Same amount of water inside and outside the cell Salt solution Distilled water

Same amount of water inside and outside the cell Plant Cells Distilled water Salt solution Same amount of water inside and outside the cell

TOPIC: CELLS AIM: HOW DOES ACTIVE TRANSPORT OCCUR? The similarities of diffusion and osmosis are ______________ _______________ The differences of osmosis are ______ DO NOW: In your own words describe the similarities and differences of diffusion and osmosis.

Active Transport Movement of molecules from an area of low concentration to an area of high concentration Against the Conc. Gradient ENERGY IS NEEDED!

L L H H

CELL MEMBRANE PROTEIN LOW (energy)

Passive Transport Active Transport What process is each cell carrying out? Passive Transport Active Transport

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) Endocytosis

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