The protein core consists of a non polar section, while the surface of the protein consists of the blue section that is basically the hydrophilic section. The hydrophilic amino acids and these water molecules will form hydrogen bonds with those hydrophilic amino acids found on the surface of that protein molecule. Now, the extent to which a given protein is soluble in water basically depends on the number of hydrophilic amino acids that are found on the surface of that protein and generally on that protein. So let's suppose we have a beaker, and in that beaker, we have pure water. And to the pure water, we add one type of protein. Now, when we add that protein to our water, the protein will dissolve.