Question

DEFINE the term hydration spheres and EXPLAIN how they relate to the fact that ions such as sodium, chlorine, etc. they cannot cross the cell phospholipid bilayer.

Answer 1

Hydration sphere: Solvent molecules make a boundary/interface that surrounding the solute molecules. When the solvent is water then it is termed as hydration sphere, while other then water is called a solvation sphere. Ex. when we dissolve salt in water, it becomes ionized and each ion (either Na⁺ or Cl^- ) is surrounded by water molecules.

The phospholipid bilayer is composed of lipids and proteins. This membrane makes the covering boundary with lipids (phospholipids) and protein molecules are embedded in such a way, that form transporters, shuttle proteins, and most important in signaling mechanisms. Na⁺ and Cl^- both are concentration-dependent and their amount is critical to the cell, as they regulate electric potential and osmoregulation in the cell, so freely they cannot cross the bilayer. Their transport needs shuttle proteins or channel proteins that regulate their influx and efflux. Chloride ions are more in the amount in the cell than anions, while Sodium ions are higher outside.