CELL MEMBRANE

FUNCTION & COMPOSITION  Forms barrier between interior and exterior of cell  Controls what comes in and out of cell  Cell to cell communication and cell recognition  Composed of:  Phospholipids  Proteins  Glycolipids & Glycoproteins  Cholesterol

 Phospholipid—a molecule composed of a charged phosphate group and two fatty acid chains PHOSPHOLIPIDS Polar Head -Phosphate group and glycerol -Hydrophilic—water loving -Forms outer boundary of cell Nonpolar Tails -Two fatty acids tails -Hydrophobic— water hating -Forms inner boundary of cell

 Two different types:  Channel proteins—allow larger molecules in/out  Carrier proteins—allow larger molecules in/out but change shape to do so PROTEINS

 Glycoprotein—sugar attached to protein embedded within cell membrane  Cell-cell communication  Glycolipid—sugar attached to phospholipid  Cell recognition GLYCOPROTEIN & GLYCOLIPID

 Embedded in phospholipid bilayer to offer stabilization CHOLESTEROL

 Fluid Mosaic Model— describes the arrangement of molecules that make up a cell membrane  “fluid”—phospholipids & proteins can drift sideways in the membrane  “mosaic”—membrane is studded with many different kinds of proteins FLUID MOSAIC MODEL

 What materials make up a cell membrane? (a)Phospholipids and proteins (b)Cholesterol and nucleic acids (c)Proteins, nucleic acids, and cholesterol (d)Phospholipids, cholesterol, and proteins UNDERSTANDING QUESTION #1

 A channel protein does which of the following? (a)Carries ions or molecules across the membrane (b)Forms tiny holes in the membrane (c)Changes shape as it transports molecules (d)All of these UNDERSTANDING QUESTION #2

 Which part(s) of a phospholipid is hydrophobic? (a)Tails only (b)Head only (c)Head and tails (d)None of these UNDERSTANDING QUESTION #3

REFERENCES  Most information from Biology, McDougal Littell (2008)