The enzyme Y catalyzes the elementary reaction

AB-->A + B
An enzyme concentration of 1.0M Y can convert a maximum of 0.5M AB to the products A and B per second.

What will happen when each of the following is added to a solution that contains 1.0M Y and 0.8M AB?
I have to state whether the rate of the solution will increase, decrease or show no change when each of the following below is added.

More AB
More Y
More A
an inhibitor
More B

More AB - No change in the rate will happen because the substrate (reactants) are already in excess!

More B, More A - Adding more products will not affect the rate.

Inhibitor - Just from the name, 'in-hibit', it will decrease the rate because it tries to stop the reaction from happening.

More Y - In this case it will increase the rate of the reaction because AB is in excess for 1 M of Y. If the substrate (AB) weren't in excess, adding more Y wouldn't change anything.

Basically, here's some info that MasteringChemistry told me (I got this exact question):

An enzyme solution is saturated when all the active sites of the enzyme molecule are full. In this case, a 1.0 M Y solution is saturated when an AB concentration of 0.5 M or greater is present. When an enzyme solution is saturated, the reaction is occurring at the maximum rate.
The addition of more substrate to a solution that contains the appropriate enzyme will generally increase the rate of the reaction. However, if the enzyme is saturated the addition of more substrate will have no effect on the rate of reaction.
Also, the addition of more enzyme to a solution that contains the appropriate substrate will generally increase the rate of reaction as long as the substrate is in excess.

More AB: The rate of the reaction will increase because there will be more substrate available for the enzyme to convert into products. It's like giving the enzyme Y a bigger buffet to feast on.

More Y: The rate of the reaction will increase because there will be more enzyme available to catalyze the reaction. It's like having more clowns in the circus - the more clowns, the more laughs!

More A: Unfortunately, the rate of the reaction will not change. The enzyme Y can only convert AB into A and B, so adding more A will not affect the rate. It's like bringing more balloons to a balloon animal-making party, but there's already a clown dedicated to making balloon animals. No extra laughs, my friend.

An inhibitor: The rate of the reaction will decrease. An inhibitor is like a party pooper, making it harder for the enzyme Y to do its job. It's like having a grumpy clown at the circus who steals all the laughs away.

More B: The rate of the reaction will not change. The enzyme Y only converts AB into A and B, so adding more B will not affect the rate. It's like bringing more pies to a clown pie-throwing competition, but there's already a clown throwing pies. No extra laughs, my friend, just more mess!

When more AB is added to the solution (1.0M Y and 0.8M AB):

- The rate of the solution will increase because the enzyme Y can convert a maximum of 0.5M AB to products A and B per second, and the initial concentration of AB (0.8M) is less than the maximum it can convert.

When more Y is added to the solution (1.0M Y and 0.8M AB):
- The rate of the solution will not change because the concentration of the enzyme Y (1.0M) is already at its maximum, and adding more of it will not make any additional difference in the rate.

When more A is added to the solution (1.0M Y and 0.8M AB):
- The rate of the solution will not change because adding more A will not affect the rate of the enzyme-catalyzed reaction. The rate only depends on the concentration of AB and the enzyme Y.

When an inhibitor is added to the solution (1.0M Y and 0.8M AB):
- The rate of the solution will decrease because an inhibitor can bind to the enzyme Y and prevent it from catalyzing the reaction. This reduces the effective concentration of Y available for the reaction, thereby decreasing the rate.

When more B is added to the solution (1.0M Y and 0.8M AB):
- The rate of the solution will not change because adding more B will not affect the rate of the enzyme-catalyzed reaction. The rate only depends on the concentration of AB and the enzyme Y.

To determine the effect of each addition on the rate of the reaction, you need to understand how the reaction is influenced by changes in the concentrations of the reactants and other substances. Here's an explanation for each case:

1. More AB:
The rate of the reaction will increase.
Explanation: The rate of the reaction is determined by the concentration of the reactants. By adding more AB, you are increasing the concentration of the reactant, which will result in a higher rate of the reaction.

2. More Y:
The rate of the reaction will stay the same.
Explanation: The concentration of the enzyme Y is already at its maximum value (1.0M), which means it is saturated. Adding more Y will not increase the rate of the reaction since it is already operating at its maximum capacity.

3. More A:
The rate of the reaction will decrease.
Explanation: The reaction is irreversible, meaning once A and B are formed, they cannot be converted back to AB. By adding more A, you are shifting the equilibrium of the reaction towards the products, causing the rate to decrease.

4. An inhibitor:
The rate of the reaction will decrease.
Explanation: An inhibitor is a substance that reduces the activity of the enzyme. By adding an inhibitor to the solution, it will bind to the enzyme Y and prevent it from catalyzing the reaction efficiently. As a result, the rate of the reaction will decrease.

5. More B:
The rate of the reaction will stay the same.
Explanation: The concentration of B does not affect the rate of the reaction since it is a product and not involved in the elementary reaction. Adding more B will not change the rate at which AB is converted to A and B.

In summary:
- Adding more AB or an inhibitor will decrease the rate of the reaction.
- Adding more Y or B will have no effect on the rate of the reaction.
- Adding more A will decrease the rate of the reaction.