Class 11 NEET Biology Cell - The Unit of Life Questions Part 1

(b) : According to the fluid mosaic model of cell membrane structure proposed by singer and Nicolson (1972) plasma membrane contains about 50−60% proteins and 50−40% lipids. Lipids form a bilayer with hydrophilic heads pointing outwards. Cell membrane allows transport of some molecules by passive transport eg., water, neutral solutes while some are transported actively e.g.,Na+∕K+ pump.