The Amphipathic Property of Phospholipids Can Be Described as a

Learning Objective

• Describe phospholipids and their function in cells

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Cardinal Points

• Phospholipids consist of a glycerol molecule, ii fatty acids, and a phosphate grouping that is modified by an alcohol.
• The phosphate group is the negatively-charged polar head, which is hydrophilic.
• The fatty acid chains are the uncharged, nonpolar tails, which are hydrophobic.
• Since the tails are hydrophobic, they face the within, away from the water and run into in the inner region of the membrane.
• Since the heads are hydrophilic, they face outward and are attracted to the intracellular and extracellular fluid.
• If phospholipids are placed in water, they form into micelles, which are lipid molecules that arrange themselves in a spherical form in aqueous solutions.

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Terms

• micelleLipid molecules that accommodate themselves in a spherical form in aqueous solutions.
• amphipathicDescribing a molecule, such equally a detergent, which has both hydrophobic and hydrophilic groups.

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Defining Characteristics of Phospholipids

Phospholipids are major components of the plasma membrane, the outermost layer of animal cells. Similar fats, they are composed of fatty acid chains attached to a glycerol backbone. Unlike triglycerides, which have iii fat acids, phospholipids take two fat acids that assist course a diacylglycerol. The third carbon of the glycerol backbone is likewise occupied by a modified phosphate group Yet, just a phosphate group attached to a diacylglycerol does not qualify as a phospholipid. This would be considered a phosphatidate (diacylglycerol 3-phosphate), the precursor to phospholipids. To qualify as a phospholipid, the phosphate group should exist modified past an alcohol. Phosphatidylcholine and phosphatidylserine are examples of two important phospholipids that are found in plasma membranes.

Phospholipid MoleculeA phospholipid is a molecule with ii fatty acids and a modified phosphate grouping attached to a glycerol backbone. The phosphate may exist modified past the improver of charged or polar chemic groups. Ii chemical groups that may modify the phosphate, choline and serine, are shown hither. Both choline and serine attach to the phosphate group at the position labeled R via the hydroxyl grouping indicated in greenish.

Structure of a Phospholipid Molecule

A phospholipid is an amphipathic molecule which means it has both a hydrophobic and a hydrophilic component. A single phospholipid molecule has a phosphate group on one terminate, chosen the "head," and two side-by-side bondage of fatty acids that make up the lipid "tails. " The phosphate group is negatively charged, making the head polar and hydrophilic, or "h2o loving." The phosphate heads are thus attracted to the h2o molecules in their surroundings.

The lipid tails, on the other hand, are uncharged, nonpolar, and hydrophobic, or "water fearing." A hydrophobic molecule repels and is repelled past h2o. Some lipid tails consist of saturated fatty acids and some contain unsaturated fatty acids. This combination adds to the fluidity of the tails that are constantly in motion.

Phospholipids and Biological Membranes

The prison cell membrane consists of two adjacent layers of phospholipids, which form a bilayer. The fatty acid tails of phospholipids face inside, away from h2o, whereas the phosphate heads face the outward aqueous side. Since the heads face outward, 1 layer is exposed to the interior of the jail cell and 1 layer is exposed to the outside. Every bit the phosphate groups are polar and hydrophilic, they are attracted to water in the intracellular fluid.

Phospholipid BilayerThe phospholipid bilayer consists of two adjacent sheets of phospholipids, bundled tail to tail. The hydrophobic tails associate with one another, forming the interior of the membrane. The polar heads contact the fluid inside and outside of the cell.

Because of the phospholipds' chemical and physical characteristics, the lipid bilayer acts as a semipermeable membrane; only lipophilic solutes can easily pass the phospholipd bilayer. As a result, in that location are 2 distinct aqueous compartments on each side of the membrane. This separation is essential for many biological functions, including jail cell communication and metabolism.

Membrane Fluidity

A prison cell's plasma membrane comprise proteins and other lipids (such as cholesterol) within the phospholipid bilayer. Biological membranes remain fluid considering of the unsaturated hydrophobic tails, which prevent phospholipid molecules from packing together and forming a solid.

If a drop of phospholipids are placed in water, the phospholipids spontaneously forms a structure known as a micelle, with their hydrophilic heads oriented toward the water. Micelles are lipid molecules that arrange themselves in a spherical class in aqueous solution. The germination of a micelle is a response to the amphipathic nature of fatty acids, pregnant that they contain both hydrophilic and hydrophobic regions.

MicellesAn example of micelles in water.

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Source: https://courses.lumenlearning.com/introchem/chapter/phospholipids/

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