Which biological molecules act as catalysts to speed up chemical reactions in the body?

• A. Lipids
• B. Carbohydrates
• C. Enzymes
• D. Nucleotides

Answer: (C)

Enzymes act as catalysts in the body by speeding up chemical reactions. They do this by lowering the activation energy, the amount of energy required to start a reaction, so processes like digestion and metabolism happen quickly without needing extra energy. Most enzymes are proteins with shaped active sites that bind specific substrates, like a lock and key, or with an induced-fit adjustment that helps the reaction proceed. Because enzymes aren’t consumed in the reaction, they can be used again and again. Their activity can be tuned by factors such as temperature, pH, and the presence of cofactors or inhibitors.

In contrast, lipids are mainly involved in energy storage and membranes, carbohydrates provide quick or stored energy and structural support, and nucleotides serve as building blocks of DNA/RNA and as energy carriers like ATP. While ATP is a nucleotide, it isn’t a general catalyst for body reactions; enzymes are the true catalysts that accelerate these processes.