Cholesterol (see structure below) and cholate (a bile acid anion, whose structure is shown on p. 731) are sterols with very similar structures. However, the roles they play in the body are different: Cholate is an emulsifier, whereas cholesterol plays an important role in membrane structure. Identify the small differences in their structures that make them well suited to their jobs in the body. Given their similar structures, can the roles of these molecules be reversed? <IMAGE>