Question

level 2
enzymes are catalysts. this means they function to
a. speed up chemical reactions
b. change the ph of the reaction medium
c. provide energy to carry out the reaction
d. slow down chemical reactions

level 2
which line shows an enzyme - catalyzed reaction?
a. line 1: it shows reactants with the most energy
b. line 1: it shows the highest energy of activation
c. line 2: it shows products with the least energy
d. line 2: it shows the lowest energy of activation

level 2
identify the molecules labelled y and z.
a. y - product, z - reactant
b. y - reactant, z - product
c. y - catalyst, z - inhibitor
d. y - catalyst, z - product

level 2
when an enzyme catalyzes a reaction,
a. it is used once and discarded
b. it acts as a reactant
c. it lowers the activation energy of the reaction
d. it raises the activation energy of the reaction

Explanation:

1. Enzymes are biological catalysts that speed up chemical reactions by lowering the activation - energy required for the reaction to occur. They do not change the pH of the reaction medium or provide energy for the reaction, nor do they slow down chemical reactions. So for the first question about the function of enzymes, the answer is based on their catalytic property of speeding up reactions.
2. In an enzyme - catalyzed reaction, the reactants bind to the enzyme's active site. The activation energy is the energy barrier that must be overcome for the reaction to proceed. Enzymes lower this activation energy. Looking at the energy - time graph, the line that shows the least energy with the lowest activation energy is the one representing the enzyme - catalyzed reaction.
3. In the diagram of the enzyme - substrate interaction, the molecule that binds to the enzyme is the reactant (substrate), and the molecule that is formed as a result of the reaction is the product. The enzyme is not used up in the reaction and can be reused. The molecule that binds to the enzyme to stop the reaction is an inhibitor. So, based on the definitions of reactant, product, and inhibitor in the context of enzyme - catalyzed reactions, we can identify the molecules.
4. Enzymes are catalysts, and catalysts are not used up in a reaction. They lower the activation energy of the reaction, allowing it to proceed more readily. They do not act as reactants themselves or raise the activation energy.

Answer:

1. A. Speed up chemical reactions
2. D. Line 2: it shows the lowest activation energy
3. B. Y - Reactant; Z - Product
4. C. It lowers the activation energy of the reaction