This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Cell volume & shape is maintained by 
Select and explain. 
A. Goldman effect, B. Gibbs - Donnan effect, C. Singer's effect, D. None
B: Gibbs - Donnan effect
Answer: B: Gibbs - Donnan effect 
Explanation: Gibbs-Donnan effect---there are more osmotically active paicles in the cells than the interstitial fluid. This would make them swell and eventually rupture, but prevented by operation of Na+-K+ pump which produces net movement of positive charge out of the cell and keeps the inside a.d outside of the cell in osmotic equilibrium. (Ref: Textbook of physiology AK Jain 5th edition page no.32)