Suppose the major solutes in intact lysosomes (a cellular organelle) are KCI (0.

Question

Suppose the major solutes in intact lysosomes (a cellular organelle) are KCI (0.1 M) and NaCl (0.03 M). We wish to isolate lysosomes from intact cells in our                     labs, such that the membrane of the lysosomes does not rupture. Assuming the experiment is performed at room temperature (25 degrees C), what concentration of                     sucrose should we use in the extracting solution to make sure the lysosomes do not rupture, with the knowledge that sucrose does not dissociate?

Explanation / Answer

Osmotic pressure P = iMRT

where i is van't Hoff factor, M is molarity, R is molar gas constant and T is temperature


KCl => K+ + Cl-

i(KCl) = 2 (since each KCl gives 2 ions)

M(KCl) = 0.1 M


NaCl => Na+ + Cl-

i(NaCl) = 2 (since each NaCl gives 2 ions)

M(NaCl) = 0.03 M


Since sucrose does not dissociate => i(sucrose) = 1


For the membanes not to rupture:

P(KCl) + P(NaCl) = P(sucrose)

i(KCl)M(KCl)RT + i(NaCl)M(NaCl)RT = i(sucrose)M(sucrose)RT

i(KCl) x M(KCl) + i(NaCl) x M(NaCl) = i(sucrose) x M(sucrose)

2 x 0.1 + 2 x 0.03 = 1 x M(sucrose)


Concentration of sucrose = M(sucrose) = 0.26 M

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