Imagine that a cell is produced with only a single phospholipid layer (instead of a bilayer). How would this change in structure

If only one layer of phospholipids exists, substances moving in and out of the cell would be regulated in a single direction, which may not effectively maintain cell shape. This alteration would likely disrupt the cell's functional capacity.

Cells require a lipid bilayer to sustain internal homeostasis. Without it, a highly hydrophilic interior may form, resulting in water retention and fat inhibition relative to the intracellular fluid. The lipid bilayers are expertly designed to facilitate selective diffusion of proteins or chemicals, thus preserving cellular equilibrium with the environment. A single-layer membrane would be deficient and ineffective, attracting only hydrophobic molecules externally, while internal hydrophilic substances would have difficulty escaping into the extracellular fluid.