Cell Transport Ch. 7.3 & 7.4

Plasma Membrane Membrane Lipids Cell membranes consist of a phospholipid bilayer

Plasma Membrane Membrane Proteins Cell membranes often contain proteins embedded within the phospholipid bilayer.

Plasma Membrane Fluid Mosaic Model the phospholipid bilayer behaves like a fluid more than it behaves like a solid.

Diffusion Chapter 4 Diffusion the movement of a substance from an area of high concentration to an area of lower concentration caused by the random motion of particles of the substance

concentration gradient passive transport movement across the cell membrane that does not require energy concentration gradient A difference in the concentration of a substance, across a space

Equilibrium equilibrium the concentration of a substance is equal throughout a space

Some substances move across the cell membrane without any use of energy by the cell.

Simple Passive Diffusion Many substances enter or leave cells by diffusing across the cell membrane.

Osmosis Chapter 4 osmosis the diffusion of water through a selectively permeable membrane determined by solute concentration on both sides of the cell

Osmosis is a type of passive transport

There are three possibilities for the direction of water movement:

Osmosis Chapter 4 Hypertonic solution solute concentration outside the cell is HIGHER THAN the cytosol there is a NET movement of water out of the cell. the cell shrinks.

Osmosis Hypotonic solution solute concentration outside the cell is LOWER THAN the cytosol there is a NET movement of water into the cell. the cell swells.

Osmosis Isotonic solution the solute concentration outside the cell is EQUAL TO the cytosol there is no NET movement of water.

Compare

Facilitated Diffusion Passive transport across the membrane using an embedded protein

Carrier proteins bind to a specific substance on one side of the cell membrane, carry the substance across the cell membrane, and release it on the other side.

a transport protein with a polar pore through which ions can pass. Ion channel a transport protein with a polar pore through which ions can pass.

Movement Against a Concentration Gradient active transport the transport of a substance across the cell membrane against its concentration gradient. Energy is required.

Comparing Active and Passive Transport

Movement in Vesicles endocytosis The movement of larger substances across the cell membrane by vesicles.

exocytosis the movement of a substance by a vesicle to the outside of a cell