Cell membranes are made up of a phospholipid bilayer. which part of the phospholipid bilayer interacts with water? which part does not interact with water?

The polar head groups of phospholipids interact with water while the hydrophobic hydrocarbon tails are packed away from the water.

Explanation:

A phospholipid contains glycerol to which hydrocarbon tails are bonded. These hydrocarbon tails make the hydrophobic region of the phospholipids and are packed away from the water to make the inner core of the membranes. Glycerol of a phospholipid also has a phosphate group attached to its third carbon. The phosphate and glycerol moiety together make the hydrophilic head part of the phospholipid and interact with the surrounding water.