Plasma Membrane  aka – Cell membrane  Separates the interior of ALL cells from the outside environment  Protects the cell

What’s it made of?  Lipid bilayer Hydrophilic heads Hydrophobic tails  Embedded proteins Channels for transport

How does it work?  Selectively Permeable  Controls movement into and out of the cell  Only allows specific molecules and ions into cell = selective = picky

Passive Transport  No energy is needed to cross cell membrane Spontaneous process  Molecules move from areas of higher concentration to lower concentration  3 types of passive transport 1. Simple diffusion 2. Facilitated diffusion 3. Osmosis

Simple Diffusion  The tendency of molecules to spread into an available space

Facilitated diffusion  Movement across membrane through special transport proteins (channels) embedded in the membrane

Osmosis  Diffusion of WATER across cell membrane

Active Transport  Energy is required to move molecules across membrane  Movement against the concentration gradient – (low to high)

Passive and Active Transport  ology1111/animations/passive1.swf ology1111/animations/passive1.swf

 Movement of molecules INTO cell  Movement of molecules OUTSIDE of cell Exocytosis Endocytosis