Which statement correctly describes why the phospholipids of the cell membrane arrange the way they do in a bilayer?
The polar heads are repelled by water, so they position themselves in the middle of the bilayer. The nonpolar tails are attracted to water, so they point outward.
The nonpolar tails are attracted to water, so they position themselves in the middle of the bilayer. The polar heads are repelled by water, so they point outward.
The polar heads are attracted to water, so they position themselves in the middle of the bilayer. The nonpolar tails are repelled by water, so they point outward.
The nonpolar tails are repelled by water, so they position themselves in the middle of the bilayer. The polar heads are attracted to water, so they point outward.
The correct statement is: The polar heads are attracted to water, so they position themselves in the middle of the bilayer. The nonpolar tails are repelled by water, so they point outward.
The correct statement describing why the phospholipids of the cell membrane arrange the way they do in a bilayer is:
"The nonpolar tails are attracted to water, so they position themselves in the middle of the bilayer. The polar heads are repelled by water, so they point outward."
To understand why this arrangement occurs, we need to look at the structure of phospholipids. Phospholipids are made up of a polar phosphate head and two nonpolar hydrophobic tails. In an aqueous environment, such as the fluid inside and outside of a cell, water molecules form hydrogen bonds with each other. This creates a net negative charge at the oxygen atom and a net positive charge at the hydrogen atoms of water.
The polar heads of phospholipids are attracted to the charged, polar water molecules because opposite charges attract each other. Thus, the polar heads arrange themselves towards the watery environments, both on the inside and outside of the cell, where they can interact with water molecules.
On the other hand, the nonpolar tails of phospholipids are composed of fatty acid chains that are hydrophobic, meaning they are not attracted to water. They are repelled by the polar water molecules and tend to avoid direct contact with water. As a result, the nonpolar tails position themselves away from the watery environments, creating a hydrophobic core in the middle of the bilayer.
This arrangement with polar heads facing outward and nonpolar tails facing inward maximizes the stability and integrity of the cell membrane while ensuring that the hydrophobic regions are protected from direct contact with water.