Passive Transport

Passive Transport: Includes diffusion, osmosis, and facilitated diffusion movement down/ with the concentration gradient, no energy is used.

Concentration gradient: measures the difference in concentrations of a substance between areas

Diffusion: Gradual spreading of molecules from areas of greater concentration to areas of lesser concentration until a dynamic equilibrium is reached.

water moves by osmosis

Molecules of perfume diffuse through the air in the classroom.

Since the cell membrane is selectively preamble, only some molecules are able to diffuse through it- water, oxygen, carbon dioxide, and some small lipids.

Facilitated Diffusion: Movement of large substances through a transport protein

-Transport proteins on cell membranes help molecules cross because they can’t cross on their own due to polar/non-polar areas of the membrane.

-Doesn’t require energy since moving down and with concentration gradient.

Transport Proteins in Facilitated Diffusion:

carrier

channel

Osmosis: Diffusion of Water across a selectively preamble membrane

3 Types of solutions:

• Isotonic
• Hypotonic
• Hypertonic

These terms are used for comparing two solutions by the concentration of the solute.

Isotonic: equal solute

water moves, but there is no net movement

fluid around the cells in the body are isotonic

Hypotonic: less solute, more water

water moves out of this solution; into the cell

outside solution is hypotonic to the cell

Hypertonic: more solute, less water

water moves into this solution; out of the cell

outside solution is hypertonic to the cell

When water moves into the cell…

Internal pressure increases

Animal cells can burst (cytolysis)

Cytolysis: occurs with the bursting of a cell due to the development of a condition of osmotic imbalance.

Plant cells have cell walls, Turgor Pressure increases, making the cell rigid.

Turgor Pressure: Pressure exerted by fluid in a cell that presses the cell membrane against the cell wall.

Hypotonic Solution

When water moves out of a cell…

Plasmolysis occurs

Plasmolysis: shrinking of (the cell membrane) cytoplasm away from the wall of a living cell due to the outward osmotic flow of water.

Animal cell shrivels

Plant cell: wilting, decrease in Turgor Pressure.

Hypertonic solution