Warm-up 9/26 (Enzyme Review)

At high temperatures, the rate of enzyme action decreases because the increased heat......

• neutralizes the acids and bases in the system

• alters the shape of the active site of the enzyme

• increases the concentration of the enzyme

• changes the pH of the system

Which enzyme would you expect to find in bacteria growing in a hot environment?

• Enzyme X

• Enzyme Y

Using the diagram, match the following.

• Active Site

• A

• Enzyme

• C

• Enzyme Substrate Complex

• E

• Substrate

• B

• Product

• D

Enzymes are capable of increasing the rate of a chemical reaction within a living cell. Enzymes accomplish this through which of the following means?

• reducing the number of products

• reducing the activation energy

• increasing the temperature of the cell

• increasing the concentration of reactants

Answer explanation

Activation energy is the energy the reaction needs to get going. Usually it is quite high, and that is why some reactions take a very long time to get going if they get going at all.

Enzymes LOWER the ACTIVATION ENERGY of a reaction, hence speeding it up!

The graph shows how enzymes affect reactions in cells. Which statement best summarizes the information shown in the graph?

• Enzymes increase the energy of the reactants.

• Enzymes decrease the energy level of the products.

• Enzyme decrease the activation energy of the reaction.

• Enzymes reverse the direction of the reaction.

Answer explanation

The graph clearly shows the reaction goes quicker when the enzyme is present and the activation energy is lowered.

Which of the following conclusions can be drawn from this graph?

• The optimum pH of the enzyme is 6.6.

• The optimum pH of the enzyme is 5.8

• The enzyme’s activity increases as pH increases 5.0 to 9.0

• The enzyme’s activity is greater around pH of 8.0 .

Answer explanation

Remember, OPTIMUM is the usually the highest point on the graph and shows the 'best' value.

Which statement best describes the enzyme represented in the graphs below?

• This enzyme works best at a temperature of 35°C and a pH of 8

• This enzyme works best at a temperature of 50°C and a pH of 12

• Temperature and pH have no influence on the activity of this enzyme

• This enzyme works best at a temperature above 50°C and a pH above 12

Answer explanation

For this question you are looking for TWO OPTIMUM values, one for temperature and one for pH.

As food travels through the digestive system, it is exposed to a variety of pH levels. The stomach has a pH of 2 due to the presence of hydrochloride acid (HCl), and the small intestine has a pH ranging from 7 to 9. Pepsin is an example of an enzyme that digests proteins in the stomach. Which of the following most likely happens to pepsin as it enters the small intestine?

• It becomes inactive.

• It begins to replicate.

• It's shape changes to engulf large proteins.

• It's activity increases to digest more proteins.

In living cells, enzymes act as catalysts, which may reduce the amount of activation energy required for a chemical reaction to occur. In the graphs below, pathway x is a solid line representing the uncatalyzed reaction (without enzyme). The dotted line shows the catalyzed reaction (with enzyme). Which graph best illustrates the changes in a reaction when the catalyst reduces the amount of energy required?

• 
• 
• 
• 

The human body maintains a temperature of around 98.6 degrees at all times. Enzymes are involved in almost every chemical reaction in the body. Which of the following describes the connection between these two statements?

• Enzymes function best at a specific temperature.

• The body needs to be warm to prevent hypothermia.

• The body is kept relatively warm to prevent too much enzyme action.

• There is no connection between the two statements.