In the plasma membrane, the phospholipid heads Group of answer choices are isotonic and do not respond to water. are hydrophobic and face inward, shielded from water. are hydrophilic and face inward, shielded from water. are hydrophilic and face outward toward the aqueous solution on both sides of the membrane. are hydrophobic and face outward toward the aqueous solution on both sides of the membrane.

hydrophilic and face outward toward the aqueous solution on both sides of the membrane

Explanation:

The cell membrane is mainly composed of phospholipids, which are arranged in a lipid bilayer. In general, phospholipids consist of a glycerol unit, a phosphate group, and two fatty acids. In a lipid bilayer, hydrophilic (polar) phosphate heads are always oriented outwards and interact with surrounding water molecules; whereas hydrophobic fatty acid tails are oriented towards the center of the lipid bilayer away from water. It is for that reason that phospholipids are considered to be amphipathic molecules, where fatty acids confer hydrophobic properties and polar phosphate groups confer hydrophilic properties.

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