Material Flow in the Cell

Semipermeable Membrane

• The Cell Membrane is a Semipermeable membrane – it keeps some things out and lets some things in.

• Protects contents

of cell from outside

world.

• Proteins are the

bouncers

What Materials can Pass?

What can come into the cell?

Oxygen & food & proteins

What goes out of the cell?

Waste materials

What is not allowed in?

Poison and waste

PASSIVE TRANSPORT

• PASSIVE TRANSPORT – ways to move material into and out of the cell without using any energy.

2 Ways:

1. DIFFUSION

2. OSMOSIS – a type of diffusion

DIFFUSION

• The main method by which small molecules move across the cell membrane.

• The molecules move from an area of HIGHER CONCENTRATION to an area of LOWER CONCENTRATION.

• Oxygen molecules commonly move into and out of the cell by Diffusion.

• USES NO ENERGY (passive transport)

BEFORE AFTER

DIFFUSION DEMO

BEFORE

AFTER

DIFFUSION

What Causes Diffusion?

• Molecules are always moving and they bump into each other.

• When they bump into each other they push each other away and spread out.

• Eventually they spread throughout the whole area.

• NO ENERGY NEEDED by cell because the molecules have energy in their vibrations.

OSMOSIS

• A special kind of diffusion

• The diffusion of water molecules through the cell membrane.

• Water still moves from HIGHER CONCENTRATION to LOWER CONCENTRATION.

• USES NO ENERGY (passive transport)

NORMAL RED BLOOD CELL

OSMOSIS

BEFORE

RED BLOOD CELL

RED BLOOD CELL

AFTER

POTATO FISH!!!!1. Take out a sheet of paper!2. Write down observations of both of your potato

slices. 3. Put your name on both cups4. Label one cup SALT and one cup FRESH5. Put the same amount of water in each cup6. Put salt in the cup that is labeled salt (amount

does not matter, just make sure it dissolves!)7. Put one potato slice in the FRESH cup and

one in the SALT cup8. We are going to leave the potatoes in their

cups over night.9. Write down your predictions. WHAT DO YOU

THINK WILL HAPPEN TO EACH OF THE POTATOES?

ACTIVE TRANSPORT

• Active Transport – USES ENERGY to move materials into and out of the cell.

• Often from LOW concentration to HIGH concentration

• For small or large particles• This requires the cell to USE ENERGY.

2 ways:

1. ENDOCYTOSIS

2. EXOCYTOSIS

ENDOCYTOSIS• USES ENERGY (active transport)

• Large particles are taken INTO THE CELL

• Particles include PROTEIN and FOOD

ENDOCYTOSIS – draw these steps

A WANTEDMOLECULE

1

STEP 1:The cell membrane touches the wanted molecule.

energyenergy

ENDOCYTOSIS

2

STEP 2:The cell wrapsitself aroundthe molecule.

energyenergy

ENDOCYTOSIS

3

STEP 3:The moleculeforms a Vacuole.

energy

ENDOCYTOSIS

4

STEP 4:The cell membranecloses.

energy

TRANSPORT PROTEINS

• These are special Proteins called Transport Proteins that are attached to the cell membrane.

• They “PICK UP” the wanted molecules inside or outside of the cell and carry them in or out using energy.

• Common Materials transported this way:– Calcium, Potassium, and Sodium.

TRANSPORT PROTEINS

BEFORE

CYTOPLASM OUTSIDE THE CELL

HIGH LOWCONCENTRATION CONCENTRATION

TRANSPORTPROTEIN

TRANSPORT PROTEINS

AFTER

USES ENERGY

CYTOPLASM OUTSIDE THE CELL

HIGH LOWCONCENTRATION CONCENTRATION