Cell Transport - Passive Transport

Passive Transport

cell does NOT require energy to move molecules across membrane

How do particles move?

high to low concentration (down a concentration gradient) until equilibrium is reached

Passive Transport

cell does NOT require energy to move molecules across membrane

How do particles move?

high to low concentration (down a concentration gradient) until equilibrium is reached

Examples of passive transport

simple diffusion (diffusion), facilitated diffusion, osmosis

simple diffusion (diffusion)

small/uncharged molecules move through phospholipids from high concentration to low concentration. ex. oxygen, CO, and some vitamins

Facilitated diffusion

movement of large or charged molecules across cell membranes through protein channels from high concentration to low concentration

protein channel examples

Channel protein, Carrier protein, aquaporins

Channel proteins move…

ions

carrier proteins move…

glucose and other monomers

aquaporins move…

water

Osmosis

the diffusion of water through selectively permeable membrane from high concentration to low concentration

osmotic pressure

driven by differences in solute concentration, the net movement of water is either in or out of the cell

Solutions can be…

Isotonic, Hypertonic, or Hypotonic

Isotonic solution

concentration of solutes is the same inside as it is outside, molecules move equally in both directions, cell stays same size, best for animal cells okay for plant cells

Hypertonic solution

solution has higher solute concentration compared to cell (less water), water molecules move out of cell to lower water concentration, cell shrinks, bad for plants and animals (generally)

Plasmolysis

cell membrane shrinks away from the cell wall in plants (when placed in a hypertonic solution)

Hypotonic solution

solution has a lower solute concentration compared to cell (more water), movement into cell, cell walls protect plant cells from bursting

Lyse

swelling and bursting of animal cells when placed in hypotonic solution