This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: membrane structure and function, Subject name: Biochemistry
The lipid bilayer of cell membrane exist as 
Select and explain. 
A. Solid, B. Semisolid, C. Gel, D. Fibres
C: Gel
Answer: C: Gel 
Explanation: The lipid bilayer shows free lateral movement of its components, hence the membrane is said to be fluid in nature. Fluidity enables the membrane to perform endocytosis and exocytosis. However, the components do not freely move from inner to outer layer or outer to inner layer (flip-flop movement is restricted). During apoptosis (programmed cell death), flip-flop movement occurs. Somewhat similar to a gel.Ref: DM Vasudevan, page no: 11