How does an enzyme work to increase the rate of reaction?
It lowers the activation energy of the reaction by offering an alternative pathway.
Why is it that enzymes catalyse only forward reactions?
Since the active site of the enzyme is shape specific for the substrate the product, having a different shape to the substrate, will not fit the active site hence the reverse reaction can not be catalysed.

How do cells use enzymes to control the production of essential compounds?
Because enzymes are so specific, each reaction in the cell has its own unique enzyme that catalyses it. By producing a specific enzyme the cell can activate a certain reaction and produce a desired product
How can competitive inhibition of an enzyme be reversed?
By increasing the amount of substrate present.
How does pH and heating influence the activity of the enzyme?
Denaturing or destruction of the secondary and tertiary structures of the enzyme take place and high temperatures or changes in pH. When the secondary or tertiary structures are disrupted the shape of the active site changes and renders the enzyme inactive.
Why does heating denature the protein but does not break the amino acids apart? Mention secondary and tertiary structures, hydrogen bonds, covalent bonds and their relative strengths.
The primary structure is composed of covalently bonded amino acids. Covalent bonds are extremely strong and require very high temperatures in order to be broken. The secondary structure is formed by hydrogen bonds. These bonds a relatively weak , when compared to covalent bonds, and are easily broken with the application of heat .

Outline a method that may be used to experimentally test whether an inhibitor was competitive or noncompetitive. Hint: Consider concentration effects and reversible vs. irreversible effects.
Hypothesis - the impact of a competitive inhibitor on an enzyme should be overcome with an increase in the concentration of substrate. If the impact of the inhibitor can be reversed it is competitive if not it must be non-competitive.
Method

Prepare 3 test tubes all identical in every way with the same amount of inhibitor, enzyme

- Test tube 1 - introduce substrate at 0.1 M and measure the rate of product formation.
- Test tube 2 - introduce substrate at 0.2 M and measure the rate of product formation.
- Test tube 3 - introduce substrate at 0.4 M and measure the rate of product formation.
Consider an inhibitor whose concentration is much less than that of the substrate. If the substrate has a greater affinity (attraction for) the active site what will happen to the effect on the formation of product?
The enzyme will not be completely inhibited. Competition will favour the substrate binding to the enzyme and hence reaction will continue.
If an enzyme has been denatured, is it likely that the enzyme has been reversibly or irreversibly impaired? Explain.
Once denatured the enzyme can not refold back to its original shape and hence the enzyme is permanently inactive.

.
1