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: DIFFUSION 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)

DIFFUSION DEMO BEFORE AFTER

DIFFUSION AFTER BEFORE

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

RED BLOOD CELL BEFORE

RED BLOOD CELL AFTER

POTATO FISH!!!! Take out a sheet of paper! Write down observations of both of your potato slices. Put your name on both cups Label one cup SALT and one cup FRESH Put the same amount of water in each cup Put salt in the cup that is labeled salt (amount does not matter, just make sure it dissolves!) Put one potato slice in the FRESH cup and one in the SALT cup We are going to leave the potatoes in their cups over night. 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: ENDOCYTOSIS EXOCYTOSIS

ENDOCYTOSIS USES ENERGY (active transport) Large particles are taken INTO THE CELL Particles include PROTEIN and FOOD

ENDOCYTOSIS – draw these steps energy energy A WANTED MOLECULE STEP 1: The cell membrane touches the wanted molecule. 1

ENDOCYTOSIS energy energy STEP 2: The cell wraps itself around the molecule. 2

ENDOCYTOSIS energy STEP 3: The molecule forms a Vacuole. 3

ENDOCYTOSIS energy STEP 4: The cell membrane closes. 4

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 CYTOPLASM OUTSIDE THE CELL HIGH LOW TRANSPORT CONCENTRATION CONCENTRATION TRANSPORT PROTEIN BEFORE

TRANSPORT PROTEINS CYTOPLASM OUTSIDE THE CELL HIGH LOW USES ENERGY CONCENTRATION CONCENTRATION USES ENERGY AFTER