Diffusion & Osmosis

Objective 2.03Movement of materials into and out

of cells.

Passive Transport• Passive Transport: Movement within the cell

that does not cost the cell any energy (ATP).– Diffusion: The movement of particles from an area of

high concentration to an area of low concentration.• Diffusion is free for the cell.• When the equilibrium is reached, the cell is in

homeostasis.

Diffusion Clip

Passive Transport• Facilitated Diffusion: a.k.a. “Helped” diffusion.

The large protein channels help bring larger molecules that can’t squeeze through the cell membrane into the cell. This process is “free” to the cell and does not require the cell to use energy ATP.

Facilitated Diffusion Clip

Transport Proteins

• There are 2 types of transport proteins:– Channel Proteins = cannot change shape (a)– Carrier Proteins = can change shape (b)

Passive Transport• Osmosis: The diffusion of water across a semi

permeable membrane. – This process if free for the cell also. Does NOT cost

the cell energy (ATP).Hypertonic Isotonic Hypotonic(Cell Shrinks) ( Dynamic Equilibrium) (Cell Swells)

65% SaltSolution 10% Salt

Solution 90% Salt Solution

20% SaltSolution 50% Salt

Solution

50% SaltSolution

Cells in Solutions

Bursts Shrivels

Turgor Pressure – Plasmolysis-cell membrane “pushes” cell membrane pulling on cell wall away from cell wall

Active Transport• Active Transport: Cells force molecules

AGAINST the concentration gradient.– This process costs the cell energy (ATP)!– Protein Chanels and Pumps are used to move

these molecules.

Sooo…