Separates:
Internal living cytoplasmic from
External environment of cell
Phospholipid bilayer:
External surface lined with hydrophilic polar heads
Cytoplasmic surface lined with hydrophilic polar heads
Non polar, hydrophobic, fatty-acid tails sandwiched between
MEMBRANE MODELS
Fluid-Mosaic Model
Three components:
Basic membrane referred to as phospholipid bilayer
protein molecules
float around like icebergs on a sea
Membrane proteins may be peripheral or integral
Peripheral proteins are found on the inner membrane surface
Integral proteins are partially or wholly embedded (transmembrane) in the membrane
Some have carbohydrate chains attached
Cholesterol
How does it do its job?
How does it let stuff through?
It's like a perfume being sprayed. Once the particles get into the air, they spread out more. That's why people across the room can smell just one spray of perfume!
Diffusion: Movement from high concentration to low concentration
Osmosis: diffusion of water across a membrane
What CAN go across a cell membrane WILL go across!
When it is warmer, the molecules move faster. So when it's colder, they must move slower and it's tougher for them to move around.
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