Diffusion and Osmosis Notes

Objective: You will be able to explain diffusion and osmosis and give an example for each one.

Itinerary:1. PowerPoint (definitions)2. Teacher demostrations

The Plasma Membrane and Homeostasis

Homeostasis – Maintaining a Balance

• Cells must keep the proper concentration of nutrients and water and eliminate wastes.

SO HOW DO THINGS GET INTO THE CELL?

The cell doesn’t have a mouth, so particles have to go through the cell membrane!

Word Definition Picture

1. Cell membrane

Surrounds cell

Semipermeable: Lets certain things in and out of cell

Food molecules

Water molecules

Wastes

Oxygen molecules

Carbon dioxide

Everything a cell needs to come in or go out has to pass through cell

membrane

The cell membrane has little spaces where things can just slip right in or out of the cell.

So….

Some substances are so small that they can slip between the membrane molecules to enter or leave the cell.

Imagine a jar full of marbles…Can you pour some sand into the jar?

The sand will fill up the space in between the marbles…that’s how some materials can get through the cell membrane.

What does passive mean?

This lady is passive!

Word Definition Picture

2. Passive Transport

No energy tomove materialsExamples:Diffusion and

Osmosis

Word Definition Picture

3. DiffusionWhen particles move from an area of high

concentration to an area of low concentration

HIGH TO LOW

Passive Transport – Diffusion

Familiar examples of diffusion:

• A skunk’s odor spreads through the neighborhood

• A spilled bottle of perfume fills the air with a strong scent

• Food coloring mixes through a beaker of water

No energy is needed for oxygen to diffuse into a cell.

• High concentration of oxygen outside of cell

• Low concentration of oxygen inside the cell

• Diffusion of oxygen into cell

• Equal concentration of oxygen outside and inside cell

No energy is needed for carbon dioxide to diffuse out of the cell.

• High concentration of carbon dioxide inside of cell

• Low concentration of carbon dioxide outside the cell

• Diffusion of carbon dioxide out of cell

• Equal concentration of carbon dioxide in and outside cell

Word Definition Picture

4. Osmosis

The diffusion of water across a

membrane

HIGH TO LOW

LOTS OF WATER TO LESS WATER

Osmosis – What is happening in this animation?

What happened to the celery? Is this diffusion or osmosis?

This celery is wilted, so we put it into water.

Less water IN celery Water flowed into celery!

It is OSMOSIS!

Your blood is similar to sea water in the amount of salt it contains.

What do you think would happen to one of your red blood cells if you placed it in pure water?

Fresh water will flow into the cell and it will burst!

Word Definition Picture

5. Equilibrium

when the moleculesof a substance are spread out evenly throughout the Space- Osmosis and

diffusion will continue until particles are equal

EXIT SLIP

1. Give definition and an example of diffusion (you may have seen some today in class)

2.Give a definition and an example of osmosis.

3.What is passive transport?

4.What is equilibrium?