Explain how these statements differ, and identify which one(s) is/are correct. Explain what is wrong with each incorrect statement. Explain when chemical reactions continue and when they stop.

Question

A. A chemical reaction proceeds until the enzyme molecules are all consumed.
B. A chemical reaction proceeds until the substrate molecules are all consumed.
C. A chemical reaction proceeds until equilibrium is established.
D. A chemical reaction proceeds until all the product molecules are removed.

Answer 1

B and C are correct as written, but B requires some clarification. A is incorrect because enzyme molecules are not consumed in chemical reactions and will continue to be active until acted upon by environmental conditions (temperature, pH, or modifiers). B is correct only when the product is removed from the system. If the product
remains, the enzyme will reach equilibrium where the ratio of substrate to product is constant (Correct Answer C). In D, if the product of the reaction is removed, the reaction would continue to proceed to form new product (assuming enzymes and substrates are available). Chemical reactions continue if conditions are favorable, including presence of substrate and enzyme and fairly constant temperature and pH. In living systems, most chemical reactions do not have a steady supply of substrate; for example, the chemical reactions of digestion will stop when
the small intestine is empty.