Question

A rough analysis of cell contents suggests their cytoplasm contains 5% by weight of solutes: 1% is proteins of average molecular weight 45,000; 1% is soluble lipids of molecular weight 400; 1% is sugars of molecular weight 170; and 2% is salts like KCl. What is the osmotic pressure inside these cells relative to pure water at 37C? Assume the density of the cytoplasm is approximately 1g/cm^3 and has the properties of water.

Answer 1

suppose vol of cytoplasm in cell = 1 litre it means 5% of weight of solutes = 5/100*1000 = 50 g

O.P.    = molar conc *R*T ....R = 8.314

for proteins ,   molar conc = 10 g/ molecular mass *1000

                O.P. due to proteins = (10/1000)/45000) * 8.314 * (273+37) = 5.727*10^-4 Pascals

                    "            soluble lipids = (10 /400*1000 )*8.314 * (273+37) = 0.0644 "

                    "           sugars     = (10/170*1000)*8.314* (273+37)   =0.1516             "

                     "          KCl    =    (20/74.5*1000) *8.314*(273+37)   = 0.6919                "