Factors that Affect Enzyme Activity

Why does the graph plateau?

• There are no available enzymes to bind to more substrates, so the rate of reaction has reached its maximum.

• The enzymes have denatured, and so the reaction has stopped.

• The products made bind to the active sites, so no more substrates can bind.

• There are no more substrates to be broken down, so the rate of reaction has reached its maximum

Which of the following best describes how substrate concentration affects enzyme action?

• The more substrate available, the faster the rate of reaction.

• As substrate concentration halves, the rate of reaction quadruples.

• As substrate concentration doubles, the rate of reaction triples.

• The less substrate available, the faster the rate of reaction.

The diagram provided shows an enzyme that has undergone a sudden change in pH. What happened to this enzyme?

• The enzyme has been destroyed.

• The enzyme has been replicated.

• The enzyme has been killed.

• The enzyme has been denatured.

Why will most enzyme-controlled reactions occur slowly at a low temperature?

• A lower temperature means the molecules have less elastic energy, so they do not bind together as frequently.

• A lower temperature means the molecules have more kinetic energy, so they collide frequently.

• A lower temperature means the molecules have less kinetic energy, so they do not collide as frequently.

• This is incorrect; most enzyme-controlled reactions will occur quickly at low temperatures.

Which of the following best explains what happens when an enzyme denatures?

• A change in the protein structure of an enzyme causes a change in the shape of the active site.

• A change in the carbohydrate structure of an enzyme causes a change in the shape of the active site.

• A change in the lipid structure of an enzyme causes a change in the shape of the active site.

• A change in the structure of an enzyme causes the active site to become permanently bound to a substrate.

Enzymes have an optimum temperature. Which of the following best defines the term “optimum temperature”?

• The optimum temperature is the temperature at which the enzyme denatures.

• The optimum temperature is the temperature at which the enzyme can replicate.

• The optimum temperature is the temperature at which the rate of reaction is the slowest.

• The optimum temperature is the temperature at which the enzyme functions best.

Which of the following changes will decrease the rate of an enzyme-controlled reaction?

• Increasing enzyme concentration

• Decreasing substrate concentration

• Decreasing product concentration

• None of the above

What is the optimum temperature for this enzyme?

• 60∘C

• 40∘C

• 50∘C

• 30∘C

What happened to the enzyme when the temperature exceeded that optimum value?

• It dissolved.

• It denatured.

• It melted.

• It freeze.

(a)   are biological catalyst that speed up the chemical reactions that take place inside all cells.