Question

in the facilitated diffusion of glucose, what determines the direction in which glucose molecules will be transported? (figure 3-18)
the amount of atp available inside the cell versus outside the cell
the tonicity of the cell
the amount of sodium available to bind inside the cell versus outside the cell
the voltage of the membrane
the concentration gradient

Explanation:

Facilitated diffusion is a passive transport process, meaning it does not require ATP (so the first option is incorrect). Tonicity relates to the osmotic pressure gradient of water, not directly to glucose transport direction (second option wrong). Sodium binding is relevant for secondary active transport of glucose, not facilitated diffusion (third option wrong). Membrane voltage is more related to ion transport, not glucose facilitated diffusion (fourth option wrong). Facilitated diffusion of glucose, like other passive transport, is driven by the concentration gradient (molecules move from high to low concentration).

Answer:

the concentration gradient