Which best describes a metabolic pathway?

• A. Nonlinear set of unrelated reactions
• B. Single step reaction
• C. Series of linked reactions
• D. Energy transfer between organisms

Answer: (C)

Metabolic pathways are sequences of enzyme-catalyzed reactions where each step uses the product of the previous one as its substrate, so the molecule is transformed step by step into a final product. This linked series lets the cell control flow, manage energy storage and release, and regulate the pathway at key points. Classic examples include glycolysis and the citric acid cycle, which proceed through multiple steps rather than a single transformation. Describing metabolism as a nonlinear set of unrelated reactions would break the idea of a connected sequence; a single-step reaction misses the progressive transformation that defines a pathway; and energy transfer between organisms reflects ecological interactions, not a single organism’s metabolic sequence. Therefore, a series of linked reactions best captures what a metabolic pathway is.