Question

1. why are the heads of the molecules on the outside of the membrane and the tails on the inside?

Explanation:

Cell membranes are made of phospholipids. Phospholipid heads are hydrophilic (water - attracting) and tails are hydrophobic (water - repelling). The external and internal environments of the cell membrane are aqueous (water - based). So, the hydrophilic heads face the water - rich outer and inner (cytoplasm - side) regions, while the hydrophobic tails cluster together inside, away from water, to form a stable bilayer structure.

Answer:

Phospholipid heads are hydrophilic (attract water) and tails are hydrophobic (repel water). The membrane’s inner (cytoplasm) and outer environments are aqueous, so heads face water (outside/inside - adjacent), tails cluster inside (away from water) to form a stable bilayer.