1. Jean and Felicia
2.4 Membranes
Functions of the plasma membrane:
Holds the cell together
Controls what comes in and out (osmosis, diffusion, active transport)
Protect the cell
Allow cells to be recognized and to recognize others (cell signaling and immunity)
Bind to cells and other organism
Site for biochemical reaction: (enzyme, areas for reaction)
Membrane and Membrane transports
Phospholipid bilayer:
Phosphate fat 2 layers
Hydrophilic phosphate heads are water attracted but Hydrophobic phosphate tails are water
repellent
Phospholipids automatically form a liposome (an enclosed sphere) when surrounded by water.
(none of the lipid tails are in contact with the water)
The fluid mosaic model: Tells us that the membrane is flexible and adaptable
Phospholipids are connected by weak attractions:
the cumulative effect = strong membrane
membranes have the freedom of movement in a horizontal plane
Phopholipid bilayers: Selectively permeable (controls entry and exit)

2. Jean and Felicia
Polar heads: attracted to polar charge
Nonpolar tails: repel any charge and prevent passage of ions