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7-3 Cell Boundaries
interactive pgs. 182-189
•What are the main functions of the cell membrane and cell wall •What happens during diffusion •What is Osmosis
The Cell Membrane (sometimes called the plasma membrane)
What it does • Regulates what enters and leaves the cell (the
doorman)
• Protects from invaders
• Provides support
What it is made of • Lipid bilayer (2 layers of lipids)
• Proteins within lipid bilayer with carbohydrates attached Allow material in or out of cell
Carbohydrates act as ID cards
Cell Walls
Plants, Algae, Fungi, and Prokaryotes
Outside Cell Membrane
Provides Support and Protection
Components
• Carbohydrates (cellulose in plants)
• Protein
Diffusion
Concentration is the amount of solute dissolved in a solution
The movement of Particles in a solution from an area of high concentration to low concentration • Until equilibrium is
reached (equal amounts on both sides of membrane)
• Does not require energy
Osmosis
Diffusion can’t occur when:
• Membrane is impermeable
• The particles are too big to move through the membrane
Osmosis
• Diffusion of water
Until concentrations are equal – isotonic
Concentrated solutions – hypertonic
Diluted solutions - hypotonic
• Water can diffuse through most membranes
Facilitated Diffusion
The movement of certain molecules through protein channels in cell membrane
Does not require energy only a concentration gradient
Active Transport
Movement against a concentration gradient
Requires Energy
• Molecular Transport
Protein pumps in the cell membrane
Ca, K, and Na
Transport of Larger Molecules
Endocytosis • Membrane folds in to
form a vacuole
• Phagocytosis- cytoplasm surrounds particle and puts it in a food vacuole
• Pinocytosis- pockets take up liquids
Exocytosis • Opposite of endocytosis
• Removes materials from cell