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