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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