What substance is found exclusively in animal tissues?

Cholesterol is a substance that is synthesized uniquely in animal tissues and does not occur in plant materials. It serves vital roles in the body, such as being a structural component of cell membranes, a precursor for steroid hormones, and essential for the synthesis of vitamin D and bile acids.

In contrast, glucose is a simple sugar that is found in both plant and animal tissues, serving as a primary energy source across both kingdoms. Protein exists in both animal and plant forms, providing essential amino acids necessary for bodily functions. Fiber, which is primarily composed of plant-based materials, is not present in animal tissues at all.

Thus, cholesterol is distinctive in its exclusive presence in animals, making it the correct choice for this question.