What are proteins that speed up chemical reactions called?

• A. Hormones
• B. Antibodies
• C. Enzymes
• D. Receptors

Answer: (C)

Enzymes are proteins that speed up chemical reactions. They act as biological catalysts by binding to specific molecules (subtrates) at their active sites, forming an enzyme–substrate complex. This arrangement lowers the activation energy—the energy required to start the reaction—so reactions occur much faster under physiological conditions. Most enzymes are proteins, and their activity can be influenced by temperature, pH, and the presence of cofactors or coenzymes that assist in achieving the right shape and function. Hormones, on the other hand, are signaling molecules; antibodies are immune proteins that bind to targets; receptors are proteins that detect signals and trigger cellular responses. None are primarily about accelerating chemical reactions.