Explain the problem of lipid digestion in a hydrophilic medium and the role of bile in overcoming this.
Lipid molecules tend to coalesce and are only accessible to lipase at the lipid-water interface. Bile molecules have a hydrophilic end and a hydrophobic end, and thus prevent lipid droplets coalescing. The maximum surface is exposed to lipases. There is a need for lipase to be water soluble and to have an active site to which a hydrophobic substrate binds