Name:________________________
Period:___________
Notes:
TRANSPORT THROUGH CELL MEMBRANES
Cells are surrounded by a semi-permeable membrane which allows some materials
to enter and exit the cell.
Only materials that are dissolved in a solution can be transported across the cell
membrane.
METHODS OF CELL TRANSPORT
 __Diffusion/Osmosis___________________________________
 __Facilitated diffusion_________________________________
 __Active Transport: endocytosis & exocytosis________________
DIFFUSION
 The movement of molecules from an area of high concentration to an area
of low concentration.
 Concentration: The number of molecules of a substance in a given volume.
 High concentration: More molecules of solute
 Low concentration: Less
 Solute:
molecules of solute
Substance that dissolves in the liquid
 Solvent: Liquid part in a solution
Concentration: amount of a solute in a given solution
 The molecules have natural random motion , which they use to move from
one area to another.
 Molecules continue to move until they reach equilibrium
 When the molecules have spread out _evenly__ the solution is said to be in
equilibrium.
DIFFUSIN ACROSS THE CELL MEMBRANE
 The cell membrane is made up of two layers of lipids and proteins.
 There are openings called __Pores___ in the cell membrane.
DIFFUSION CAN OCCUR ONLY IF:
 The concentration on one side of the cell is _higher____ and the
concentration on the other side is _lower_____
 Molecules must be __smaller____ than the pores in the cell membrane
 Diffusion is passive: The cell does not use its own energy to move the
molecules.
OSMOSIS:
 The diffusion on ONLY __water___ molecules.
 Water moves from an area of _high__ concentration to an area of
_lower___ concentration.
 A cell will___burst________ if too much water enters
 The cell will__shrink_____ if too much water leaves.
 Dilute solution: very _high___ number of water molecules, low number of
solute molecules.
 Concentrated solution: very low number of ___water molecules._
1. Passive Transport:
 No energy required
 Ex: Diffusion, Osmosis and facilitated diffusion
 Facilitated diffusion: Movement of molecules across a semi-permeable
membrane with a _transport proteins___. Used to move large molecules
2. Active Transport:




The movement of substances across a cell membrane using _energy___
Move substances from _Low____ to __hign___ concentration
Endocytosis: molecules __enters_________ the cell.
Exocytosis: molecules __exit____ the cell.