system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Cell volume & shape is maintained by
assistant
The correct answer is  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)