Ms Levasseur Biology PLASMA MEMBRANE Plasma Membrane aka

Ms. Levasseur Biology PLASMA MEMBRANE

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 � http: //www. northland. cc. mn. us/biology/bi ology 1111/animations/passive 1. swf

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