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

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