why must solutes move across a lipid bilayer
A major component ofevery membrane is a collection of proteins that floaton or in the lipid bilayer. These proteins provide pas-sageways that allow substances and information tocross the membrane. Many membrane proteins arenot fixed in position; they can move about, as thephospholipid molecules do.smosis is the diffusion of water, but not solutes,across a membrane.Chapter 6 Membranes 115 UreamoleculeWatermoleculesSemipermeablemembrane FIGURE 6.16How solutes create osmotic pressure. Charged or polar substances are soluble inwater because they form hydrogen bonds withwater molecules clustered around them.