![]() The phosphate groups are also attracted to the extracellular fluid. Intracellular fluid (ICF) is the fluid interior of the cell. Because the phosphate groups are polar and hydrophilic, they are attracted to water in the intracellular fluid. The phospholipid heads face outward, one layer exposed to the interior of the cell and one layer exposed to the exterior ( ). The lipid tails of one layer face the lipid tails of the other layer, meeting at the interface of the two layers. The cell membrane consists of two adjacent layers of phospholipids. Unsaturated fatty acids result in kinks in the hydrophobic tails. The hydrophilic portion can dissolve in water while the hydrophobic portion can trap grease in micelles that then can be washed away.Ī phospholipid molecule consists of a polar phosphate “head,” which is hydrophilic and a non-polar lipid “tail,” which is hydrophobic. In fact, soap works to remove oil and grease stains because it has amphipathic properties. An amphipathic molecule is one that contains both a hydrophilic and a hydrophobic region. Phospholipids are thus amphipathic molecules. This combination adds to the fluidity of the tails that are constantly in motion. ![]() Some lipid tails consist of saturated fatty acids and some contain unsaturated fatty acids. The lipid tails, on the other hand, are uncharged, or nonpolar, and are hydrophobic-or “water fearing.” A hydrophobic molecule (or region of a molecule) repels and is repelled by water. The phosphate heads are thus attracted to the water molecules of both the extracellular and intracellular environments. ![]() The phosphate group is negatively charged, making the head polar and hydrophilic-or “water loving.” A hydrophilic molecule (or region of a molecule) is one that is attracted to water. Cholesterol is also present, which contributes to the fluidity of the membrane, and there are various proteins embedded within the membrane that have a variety of functions.Ī single phospholipid molecule has a phosphate group on one end, called the “head,” and two side-by-side chains of fatty acids that make up the lipid tails ( ). The cell membrane is an extremely pliable structure composed primarily of back-to-back phospholipids (a “bilayer”). Structure and Composition of the Cell Membrane ![]()
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