Which statement best describes the relationship between structure and function?

• A. They are unrelated
• B. Structure determines function
• C. Function determines structure
• D. They vary independently

Answer: (B)

The main idea here is that the shape and arrangement of a body part determine what it can do. In biology, form sets function because the way something is built provides the physical basis for its job. For example, the lungs are structured with many tiny alveoli and a large surface area to maximize gas exchange; bones have a rigid, dense matrix that supports the body and acts as levers for movement; neurons have long, branched fibers and insulated pathways that allow rapid electrical signaling; enzymes have specific active sites that fit particular substrates, directing which chemical reactions occur. When structure is well-suited to a task, the function it performs is efficient and effective. While activity and use can lead to structural changes over time (like muscles growing with exercise or bones remodeling under load), the core relationship is that structure enables and constrains function.