What type of substance speeds up metabolic reactions in the body?

The substance that speeds up metabolic reactions in the body is an enzyme. Enzymes are biological catalysts that facilitate biochemical reactions without being consumed in the process. They lower the activation energy required for reactions to occur, which significantly accelerates the rate at which metabolic processes happen within cells.

For example, enzymes are critical in digestion, where they break down food molecules into usable forms such as glucose. Each enzyme is specific to a particular reaction or type of reaction, ensuring that metabolic pathways are efficiently regulated and carried out. This specificity and efficiency are essential for maintaining proper physiological function and homeostasis in the body.

While hormones, catalysts, and neurotransmitters all play important roles in the body, they do not serve the same function as enzymes when it comes to directly speeding up metabolic reactions. Hormones often regulate processes and act as signaling molecules, catalysts can be non-biological substances that speed up reactions, and neurotransmitters are involved in cell communication but do not directly enhance metabolism in the manner that enzymes do.