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Wedged between phospholipid molecules in the plasma membrane of animal cells.

Cell-cell recognition is a cell’s ability to distinguish one type of neighboring cell from another.Interact with the surface molecules of other cells, facilitating cell-cell recognition.The phosphate and polar groups are hydrophilic (polar head) while the hydrocarbon chains of the 2 fatty acids are hydrophobic (nonpolar tails).The third –OH joins to a phosphate group which joins, in turn, to another polar group of atoms. In phospholipids, two of the –OH groups on glycerol are joined to fatty acids.Phospholipids Choline Hydrophilic head Phosphate Glycerol Hydrophobic tails Fatty acids Hydrophilic head Hydrophobic tails Space-filling model Structural formula Phospholipid symbol Is fluid, allowing proteins to move around within the bilayer.Mainly 2 layers of phospholipids the non-polar tails point inward and the polar heads are on the surface.Phospholipid Bilayer Polar hydro-philic heads Nonpolar hydro-phobic tails Polar hydro-philic heads Nicolson proposed the Fluid Mosaic Model of membrane structure These function as cell identity markers.įluid Mosaic Model Extracellular fluid Glycoprotein Glycolipid Carbohydrate Cholesterol Transmembrane proteins Peripheral protein Cytoplasm Filaments of cytoskeleton On the external surface, carbohydrate groups join with lipids to form glycolipids, and with proteins to form glycoproteins.Cell membranes are composed of a lipid bilayer with globular proteins embedded in the bilayer.All cells are surrounded by a plasma membrane.