Which of the following substances is NOT typically found in cell walls?

Cholesterol is not typically found in cell walls, which is why it is the correct answer. Cell walls are primarily composed of polysaccharides like cellulose, hemicellulose, and pectin, along with other structural components such as lignin in some plant tissues. Cholesterol, on the other hand, is a type of lipid mainly found in biological membranes, particularly in animal cells, where it plays a critical role in membrane fluidity and structure. Its presence is associated with cell membranes rather than cell walls, which serve primarily for support and protection. This distinction in functions and structures is fundamental in understanding cell biology and the composition of different cellular components.