Final answer:
The direction of glucose transport across a phospholipid bilayer is determined by the concentrations of glucose on either side of the membrane.
Step-by-step explanation:
Passive transport of molecules or ions depends on their ability to pass through the membrane and the existence of a concentration gradient. For polar molecules like glucose, facilitated transport is used, where molecules move down the concentration gradient through specific protein channels in the membrane without requiring energy. The direction of glucose transport across a phospholipid bilayer is determined by the concentrations of glucose on either side of the membrane, as it will move from an area of higher concentration to an area of lower concentration.