Diagram of a plasma membrane showing the modified fluid-mosaic model. The plasma membrane is a lipid bilayer consisting primarily of phospholipid molecules, cholesterol, and protein molecules. The hydrophobic fatty acid chains of phospholipids face each other to form the inner portion of the membrane, while the hydrophilic polar heads of the phospholipids form the extracellular and intracellular surfaces of the membrane. Cholesterol molecules are incorporated within the gaps between phospholipids equally on both sides of the membrane. Note the asymmetric distribution of specific phospholipids in the membrane bilayer (indicated by the different colors of the phospholipid heads). The diagram also shows integral membrane proteins and peripheral membrane proteins. Carbohydrate chains attach to both integral and peripheral membrane proteins, forming glycoproteins, and to polar phospholipid heads, forming glycolipids.

carbohydrates cholesterol molecule hydrophobic fatty acid chain

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