The Plasma MembraneThe Plasma Membrane

Structure and functionStructure and function

The phospholipid bilayerThe phospholipid bilayer

2 layers of phospholipid molecules2 layers of phospholipid molecules– ““head” is hydrophylichead” is hydrophylic– ““tail” is hydrophobictail” is hydrophobic

Semipermeable!Semipermeable!

Semipermeable Semipermeable refers to the refers to the fact that the fact that the membrane membrane only allows only allows certain certain particles to particles to pass through.pass through.

DiffusionDiffusion

Particles naturally will spread out to Particles naturally will spread out to fill a space evenly.fill a space evenly.

OsmosisOsmosis Water will naturally move from hypotonic Water will naturally move from hypotonic

to hypertonic.to hypertonic. This will continue until isotonicity is This will continue until isotonicity is

reached.reached.

Passive ProcessesPassive Processes

““Passive” refers to not requiring Passive” refers to not requiring energy.energy.– Only possible when moving particles in Only possible when moving particles in

the direction of natural diffusion. (With the direction of natural diffusion. (With the Concentration Gradient)the Concentration Gradient)

Proteins Proteins imbedded in the imbedded in the membrane form membrane form channels channels allowingallowing larger larger particles particles throughthrough

Active TransportActive Transport

Proteins imbedded in the Proteins imbedded in the membrane force partices against membrane force partices against the concentration gradientthe concentration gradient

Other functions of the membraneOther functions of the membrane

Glycoproteins serve Glycoproteins serve as identification.as identification.

Proteins serve as Proteins serve as anchors for the anchors for the cytoskeleton.cytoskeleton.

Proteins bind cells to Proteins bind cells to one anotherone another

Functions ReviewFunctions Review

Complete Picture of the MembraneComplete Picture of the Membrane