OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What are the main features of bone?

1. Elastic and compressible

2. Solid and resistant to deformation

3. Liquid and flexible

4. Thin and fragile

The correct answer is: Solid and resistant to deformation

Bone is primarily composed of a matrix that includes collagen fibers and mineralized components such as hydroxyapatite, a form of calcium phosphate. This structure gives bone its main features of being solid and resistant to deformation. The collagen provides tensile strength, allowing bones to withstand pulling forces, while the mineral content provides the rigidity necessary to resist compression and bending forces. These characteristics make bone an ideal material for supporting the body's structure, protecting vital organs, and enabling movement by providing leverage for muscles. The rigidity of bone combined with its toughness allows it to bear weight and withstand impacts without easily fracturing. This is especially important for the skeletal system, where bones must endure various stresses during daily activities like walking, running, and lifting. In contrast, the other choices describe materials that do not accurately represent bone. For example, elastic and compressible materials can easily change shape under pressure, which is not a property of bone. Liquid and flexible characteristics are typical of fluids, irrelevant to bone structure. Thin and fragile descriptions imply a structure unable to support weight or withstand stress, which contradicts the fundamental solidity and resilience of bones.