Parts of the Cell membrane








Function

Controls what enters and leaves the cell as it is selectively permeable.

 
Selectively Permeable Membrane
 
Allows small molecules to enter but NOT large molecules as they are too big
​
to fit through gaps in membrane.









Visking Tubing Experiment

Small molecules pass out of visking tubing into surrounding water

Larger molecules can't pass through visking tubing's selectively permeable membrane

 

Types of Transport

 
 
 
 
 
 
 
  1.  Passive Transport    (osmosis & diffusion)

Molecules move from higher concentration to lower concentration across the membrane down the concentration gradient.

No ATP OR membrane proteins are  required to diffuse molecules across the membrane.








   2.  Active Transport

Molecules/ions move from lower concentration to higher concentration across
the membrane against/up their concentration gradient.

ATP & membrane proteins are required for active transport.