Question

a. what effect does an enzyme have on e_a?
b. label δg. is it positive or negative?
c. how is δg affected by the enzyme?

Explanation:

Step1: Effect on activation energy

Enzymes lower the activation - energy ($E_A$). They act as catalysts and provide an alternative reaction pathway with a lower energy barrier.

Step2: Determine $\Delta G$

$\Delta G$ is the change in free - energy. In the given reaction (assuming a spontaneous reaction as depicted by the energy profile), the products have lower free - energy than the reactants, so $\Delta G<0$ (negative). To label it, we mark the difference in free - energy between the reactants and products on the energy diagram.

Step3: Effect of enzyme on $\Delta G$

An enzyme does not affect $\Delta G$. $\Delta G$ is determined by the free - energy of the reactants and products and is a state function. Enzymes only affect the rate of the reaction by lowering $E_A$, not the thermodynamics represented by $\Delta G$.

Answer:

a. An enzyme lowers $E_A$.
b. $\Delta G$ is negative. Mark the difference in free - energy between reactants and products on the energy diagram.
c. An enzyme does not affect $\Delta G$.