This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
True about facilitated diffusion are all except: 
Select and explain. 
A. Occur in direction of concentration gradient., B. Does not require energy., C. Occur in direction opposite to electrical gradient., D. Facilitated by charge of molecule.
C: Occur in direction opposite to electrical gradient.
Answer: C: Occur in direction opposite to electrical gradient. 
Explanation: Ganong 22 –31
When carrier proteins move substances in the direction of their chemical or electrical gradient, no energy input is required and the process is called facilitated diffusion.
Diffusion- process in which solute particles move from a more concentrated environment to a less concentrated one in order to bring a uniform concentration throughout.