Cellular Transport All materials entering or leaving the cell

must pass through which organelle?I. Cell Membrane

A. Function1. Provides support and protection2. Semipermeable membrane that regulates

what molecules and ions enter and leave the cell

3. Keeps the cell in a stable state called homeostasis

4. Cell recognition

B. Structure1. Flexible, double-layered sheet called a lipid

bilayera. Comprised of hydrophilic phosphate heads

and hydrophobic hydrocarbon tails

2. Proteins embedded in the bilayer act as channels and pumps that help move materials across the cell membrane

3. Carbohydrates attached to the proteins act as chemical ID cards, allowing cells to identify each other

Draw Figure 7-12 on page 182 in your textbook

Outside of cell

Inside of cell(cytoplasm)

Cell membraneProteins

Protein channelLipid bilayer

Carbohydratechains

C. Factors affecting membrane permeability1. Size2. Solubility in lipids3. Ionic charge4. Presence of carrier proteins

Do you understand the concept of concentration?

• What is the concentration of the above solution?– 20% Sugar solution

• What is the solvent? – Water

• What is the solute?– Sugar

• How can I make the solution more concentrated?– Add more sugar or less water

• Why don’t we call this an 80% water solution?

II. Passive Processes - No energy required

A. Diffusion- movement of molecules from an area of high concentration to low.

B. Facilitated Diffusion - Carrier proteins assist the diffusion of materials (e.g. glucose)

Which way will the ammonia flow?

Diffusion Movie

Which way will the water flow?

H2OH2O

H2O

C. Osmosis - The movement of water through a selectively permeable membrane in the direction of the highest solute concentration (aka - the diffusion of water).

Osmosis Movie

DRAW FIG 7-16, pg. 186

III. Active Processes - energy requiredA. Active Transport - the movement of

molecules across membrane from low concentrations to higher concentrations (against the concentration gradient).

1. At rest, cells use up to 40% of their energy for this process.

2. Carried out by membrane proteins

Molecule tobe carried

Moleculebeing carried

Energy

DRAW FIG 7-19, pg. 189

Active Transport Movie

B. Endocytosis - surrounding a substance with some of the cell membrane then bringing it into the cell within a vacuole.

1. Phagocytosis - Solids

2. Pinocytosis- Liquids

C. Exocytosis – opposite of endocytosis.

DRAW

Endo/Exocytosis Movie