Which term describes a reaction that requires energy input to synthesize complex molecules?

• A. Endergonic reaction
• B. Exergonic reaction
• C. ATP cycle
• D. Anabolic reaction

Answer: (D)

Anabolic reactions build larger, more complex molecules from smaller ones and require energy input to form new bonds. That makes this the term that best fits a reaction that uses energy to synthesize complex molecules. Energy is often supplied by ATP during these processes, fueling the assembly of proteins, nucleic acids, and polysaccharides. Exergonic reactions release energy and typically break down molecules, so they aren’t about synthesis. While endergonic describes a reaction that absorbs energy, it’s a broader energy-flow descriptor rather than the specific process of constructing larger molecules. The ATP cycle is a whole metabolic process, not a single reaction type describing synthesis.