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2.1.5 (Cell membrane structure (Formed from phospholipid bilayer…
2.1.5
Cell membrane structure
Plasma membrane
Separates cell from its external environment
1972- Singer and Nicolson proposed model
Fluid-mosaic model
Fluid= phospholipids free to move
Mosaic= proteins in bilayer vary in shape, size and position
Formed from phospholipid bilayer
Hydrophilic phosphate head (attracted to water)
Hydrophobic phosphate tail (attracted to fats/ lipids)
Intrinsic proteins
Channel proteins (hydrophilic channel)
Passive movement of polar molecules and ions down concentration gradient
Held in position by interactions between the hydrophobic core of the membrane and the hydrophobic R groups on the outside of proteins
Carrier proteins
Passive transport (down concentration gradient)
Active transport (against concentration gradient) into cells
Shape of the protein often has to change
Glycoproteins
