Cell Membrane Transport

  • Our cell membranes are selectively permeable.

–Selectively permeable: the cell membrane chooses what can and can’t pass through

•Example: sifter, strainer, etc.

Passive Transport!

•When a particle passes across the cell membrane without using energy

–Three types:

•Diffusion

•Osmosis

•Facilitated Diffusion

Diffusion

•When particles move from an area where they are more crowded to an area where they are less crowded.

–The crowding here is called CONCENTRATION

–When the concentration is the same through the system, the system is sadi to have reached EQUILIBRIUM

POPCORN!!!

•What symbolized concentration?

•What symbolized diffusion?

•What symbolized equilibrium?

Osmosis!

•The diffusion of water through a cell membrane

•Isotonic solutions: when the concentration of the cell and the solution surrounding the cell are the same – at equilibrium

–There is still the travel of water through the cell membrane, but it enters and exits at an equal rate.

Hypotonic Solutions!

•When the concentration of the water in the cell is less than the concentration of water outside of the cell

–The water from the solution surrounding the cell diffuses INTO the cell

**This causes the cell to swell and become LARGER** HYPOpotamus

Hypertonic Solutions!

•When the concentration of the water in the cell is more than the solution surrounding the cell

–The water from the cell moves OUT of the cell into the solution

**This causes the cell to shrivel and shrink!** HYPERactivity and losing weight 

Facilitated Diffusion

•To facilitate is to help just as I facilitate your learning- some particles need assistance in diffusion.

•Transport proteins assist some particles in their diffusion.

–Transport proteins allow the particles to travel through the cell membrane.

–This of a taxi cab. They transport people!

Active Transport!

•When a cell uses energy to transport from areas of low concentration to high concentration

–Think of a hot air balloon!

Two types of active transport

•Endocytosis (IN): when a particle approaches the cell, the cell membrane wraps around the particle and a vesicle pinches off bringing the particles into the cell.

•Exocytosis (EXIT): when a vesicle of particles approach the cell membrane from inside the cell and the cell releases the particles.