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1.1 Membrane Structure and Composition

1.1 Membrane Structure and Composition


Biological membranes are bilipid layers . In a real cell the membrane phospholipids create a spherical three dimensional lipid bilayer shell around the cell. However, they are often represented two-dimensionally as:

Each represents a phospholipid. The circle, or head, is the negatively charged phosphate group and the two tails are the two highly hydrophobic hydrocarbon chains of the phospholipid. The tails of the phospholipids orient towards each other creating a hydrophobic environment within the membrane. This leaves the charged phosphate groups facing out into the hydrophilic environment. The membrane is approximately 5 nm thick. This bilipid layer is semipermeable, meaning that some molecul