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