How do enzymes function in biological reactions?

Enzymes are pivotal in catalyzing biological reactions primarily by lowering the activation energy required. Activation energy is the energy threshold that must be overcome for a reaction to proceed. By reducing this barrier, enzymes enhance the rate of reactions, allowing them to occur more efficiently under the physiological conditions of living organisms.

Enzymes achieve this by stabilizing the transition state, effectively making it easier for the reactants to convert into products. This process allows reactions to happen more rapidly than they would in the absence of an enzyme. As a result, enzymes play a crucial role in various biochemical pathways, facilitating vital processes such as metabolism and DNA replication.

In contrast, the other options do not accurately reflect the role of enzymes in biological systems. Increasing activation energy would slow down reactions, making it less favorable for reactions to occur. Acting as reactants is not a function of enzymes, as they typically remain unchanged after the reaction and can be used repeatedly. Lastly, while enzymes may interact with reactants to stabilize them, their primary function is to lower the activation energy rather than increase the stability of the reactant molecules.