All Movement, Including That of Diffusing Molecules, Requires a Small

question 60

Multiple Choice

All movement, including that of diffusing molecules, requires a small expenditure of energy; what is the source of the energy that makes diffusion across the cell membrane possible?

• A)Cells hydrolyze ATP to provide the energy for diffusion.
• B)A small percentage of the diffusing molecules react chemically with the membrane.
• C)Thermal energy is present in the extracellular environment.
• D)Gravity forces the molecules to move downhill.