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Phospholipids are major components of cell membranes

Phospholipids are major components of cell membranes - The...

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Phospholipids are major components of cell membranes. Phospholipids  have two fatty acids attached to glycerol and a phosphate group at the  third position. The phosphate group carries a negative charge. Additional smaller groups may be attached to the phosphate group to form a variety of  phospholipids. The interaction of phospholipids with water is complex. The fatty acid tails are hydrophobic, but the phosphate group and its attachments form a  hydrophilic head. When phospholipids are added to water, they self-assemble into assemblages with the  hydrophobic tails pointing toward the interior. This type of structure is called a micelle. Phospholipids are arranged as a bilayer at the surface of a cell. Again, the hydrophilic heads are on the outside of the bilayer, in contact with the aqueous  solution, and the hydrophobic tails point toward the interior of the bilayer.
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Unformatted text preview: The phospholipid bilayer forms a barrier between the cell and the external environment. Phospholipids are the major component of all cell membranes. Steroids include cholesterol and certain hormones. Steroids are lipids with a carbon skeleton consisting of four fused rings. Different steroids are created by varying functional groups attached to the rings. Cholesterol, an important steroid, is a component in animal cell membranes. Cholesterol is also the precursor from which all other steroids are synthesized. Many of these other steroids are hormones, including the vertebrate sex hormones. While cholesterol is an essential molecule in animals, high levels of cholesterol in the blood may contribute to cardiovascular disease. Both saturated fats and trans fats exert their negative impact on health by affecting cholesterol levels....
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