Question

which of the following statements is correct?
the hydrophilic, or \water - loving,\ areas of lipids are in contact with the aqueous fluid both inside and outside the cell.
hydrophobic, or water - hating molecules, tend to be polar.
the hydrophilic regions of the phospholipids tend to form phosphodiester bonds with water and other polar molecules on both the exterior and interior of the cell.
none of the above

Explanation:

• For the first statement: Lipids in the cell membrane (like phospholipids) have hydrophilic heads. The cell is surrounded by extracellular aqueous fluid and has intracellular aqueous fluid (cytoplasm). So, the hydrophilic areas of lipids (e.g., phospholipid heads) interact with these aqueous fluids.
• For the second statement: Hydrophobic molecules are non - polar. Polar molecules have partial charges (due to differences in electronegativity) and can interact with water (which is polar). Hydrophobic molecules, like non - polar hydrocarbons, avoid water.
• For the third statement: Phosphodiester bonds are not formed between the hydrophilic regions of phospholipids and water. Phosphodiester bonds are covalent bonds (e.g., in the backbone of nucleic acids, where a phosphate group is linked to two sugar molecules). The interaction between hydrophilic phospholipid heads and water is through hydrogen bonds (not phosphodiester bonds).

Answer:

The hydrophilic, or "water - loving," areas of lipids are in contact with the aqueous fluid both inside and outside the cell.