Question

question 1-19 which statement best describes how enzymes affect the speed of a metabolic reaction? enzymes prevent products from being converted back into reactants, which decreases the speed of the reaction. enzymes increase the concentration of reactants, which increases the speed of the reaction. enzymes decrease the energy needed to start a reaction, which increases the speed of the reaction. enzymes replace the reactants in a chemical reaction, which decreases the speed of the reaction.

Explanation:

Enzymes are biological catalysts. They lower the activation - energy required for a reaction to start. By reducing this energy barrier, more reactant molecules can participate in the reaction, increasing the reaction rate.

Answer:

Enzymes decrease the energy needed to start a reaction, which increases the speed of the reaction.