Urea concentration in the phospholipid bilayer is 0.02mM, 3.65mM in cytoplasm, what is the urea partition coefficient in these two liquids? Solution Partition coefficient of urea (relative solubility of urea in lipid to aqueous layer) = The concentration in the phospholipid bilayer / The concentration in the cytoplasm Partition coefficient of urea is = 0.02mM/ 3.65mM = 1:182.5 mM (phospholipid: cytoplasm)..