Final answer:
The plasma membrane consists of a phospholipid bilayer with hydrophilic heads facing the aqueous environments both inside and outside the cell, and hydrophobic tails facing inwards, away from water.
Step-by-step explanation:
The plasma membrane plays a critical role in maintaining the cell's structure and providing selective permeability. Its core structure comprises a phospholipid bilayer, with hydrophilic (water-loving) heads and hydrophobic (water-fearing) tails. The hydrophilic heads of the phospholipids are attracted to the water molecules found in both the intracellular fluid (inside the cell) and the extracellular fluid (outside the cell), orienting themselves towards these aqueous environments. This results in the hydrophilic heads facing outward, towards both the cell's exterior and interior. The hydrophobic tails, on the other hand, face each other on the interior of the bilayer, creating a non-polar region that repels water and is critical for the membrane’s integrity in its aqueous surroundings.
This structure is essential for the plasma membrane's function; it provides a barrier that separates the internal cellular environment from the external one while still allowing for the selective transport of substances into and out of the cell. Hence, this characteristic amphipathic nature of the plasma membrane facilitates various biological processes necessary for cell survival.