Question

The solute molecules can cross the phospholipid bilayer of cell membrane with the help of protein because

• A. Energy is being expended by the cell
• B. The solute is moving against its concentration gradient
• C. The solute molecules are hydrophilic
• D. The cell is in a hypotonic solution
• E. Solute concentration is higher inside than outside the cell

Answer 1

The correct option is C The solute molecules are hydrophilic

The plasma membrane which consists of lipids and proteins regulate the movement of molecules in and put off the cell. Molecules can pass through cell membranes because they dissolve in the lipid bilayer. Such molecules are called lipophilic molecules. The phospholipid bilayer of the plasma membrane is scattered throughout the membrane forming a mosaic pattern. Further, these phospholipids have a hydrophobic end and hydrophilic end. While hydrocarbons and oxygen can pass through the membrane, some larger molecules cannot. The transport proteins or carrier proteins make it possible for molecules and ions to pass through the phospholipid bilayer. These proteins have the hydrophylic tunnel which allows the polar molecule to pass through. Thus, the correct answer is option C.