7.1 Enzyme Structure and Function

Question 1

What is an Enzyme?

Answer 1

A biological catalyst (usually a protein) that speeds up chemical reactions by lowering the activation energy.

Question 2

Define Substrate.

Answer 2

The specific reactant that an enzyme acts upon.

Question 3

What is the Active Site?

Answer 3

The specific region on the enzyme where the substrate binds; its shape is complementary to the substrate (Lock and Key or Induced Fit).

Question 4

What is Activation Energy?

Answer 4

The minimum amount of energy required to start a chemical reaction. Enzymes lower this threshold.

Question 5

Contrast Hydrolysis and Dehydration Synthesis.

Answer 5

Hydrolysis: Adding water to break a polymer into monomers. Dehydration Synthesis: Removing water to join monomers into a polymer.

Question 6

What are the key properties of enzymes?

Answer 6

1. They are specific (only work with one substrate). 2. They are reusable (not consumed in the reaction). 3. They are mostly proteins (subject to denaturation).

Question 7

Describe the shape of a graph illustrating the relationship between reaction rate and substrate concentration. Explain why the relationship exists.

Answer 7

Increases linearly, then plateaus (levels off). As substrate increases, reaction rate increases since the amount of successful collision will increase until all active sites are occupied (saturation).

Question 8

Describe the shape of a graph illustrating the relationship between reaction rate and enzyme concentration. Explain why the relationship exists.

Answer 8

Increases linearly, then plateaus (levels off). As enzyme concentraion increases, reaction rate increases since the amount of successful collision will increase. The substrate concentration is the limiting factor in this case.

Question 9

Describe the shape of a graph illustrating the relationship between reaction rate and temperature. Explain why the relationship exists.

Answer 9

A “bell-like” curve that drops off sharply after the peak. Activity increases with heat (more collisions since warmer molecules have more energy and move faster) until an optimal point Beyond that, the enzyme denatures. This alters the shape of the active site making it less able to interact with the substrate.

Question 10

Describe the shape of a graph illustrating the relationship between reaction rate and pH concentration. Explain why the relationship exists.

Answer 10

A more symmetrical bell curve centered at the optimum pH. Enzymes work best at a specific pH (optimum). Deviations in either direction cause denaturation to different degrees, making it more difficult for the enzyme to interact properly with the substrate.

Question 11

How would you maximize enzyme activity? To reach the V-max (maximum velocity), you should:

Answer 11

Maintain the optimal temperature and optimal pH, increase concentration of substrate so active sites are never empty, esure a high enzyme concentration, add any necessary activators (cofactors/coenzymes) and limit inhibitors

Question 12

How would you minimize or stop enzyme activity?

Answer 12

Denature the enzyme by significantly increasing the temperature of moving the pH far from optimal pH, introduce inhibitors (competitive or non-competitive), prevent addition of activators

Question 13

Compare and contrast the function inhibitors and activators.

Answer 13

They can bind to the enzyme at the active site or away from the active site in order to alter the shape of the active site and affect its ability to bind with substrates. Activators will change the enzyme structure so that substrate molecules can bind, Inhibitors will change the enzyme structure so that substrate molecules bind less successfully or not at all.

Question 14

Why is it important to regulate enzymes?

Answer 14

To prevent waste of resources of molecules and energy, so that molecules get made only when needed

Question 15

What is the different between competitive and noncompetitive inhibition?

Answer 15

competitive inhibitors block the active site (compete with substrate for the active site) while noncompetitive inhibitors bind to a different location on the enzyme (allosteric site), changing the enzyme’s shape.

Question 16

Adding higher concentration of substrate will limit the effects of which type of inhibitor and why?

Answer 16

you can “out-compete” a competitive inhibitor by adding more substrate. If it’s Non-competitive, adding more substrate won’t help because the active site shape has changed!

Question 17

An enzyme functions as a biological catalyst. How does it specifically speed up a chemical reaction?

Answer 17

by lowering the activation energy required to break bonds in the substrate(s)

Question 18

In a graph showing reaction rate vs. substrate concentration, the curve eventually levels off into a horizontal line (plateau). What is the biological reason for this plateau?

Answer 18

all available active sites are occupied by substrates

Question 19

If a researcher adds a molecule that binds to an enzyme at a location other than the active site, causing the active site to change shape, what has occurred?

Answer 19

non-competitive (allosteric) inhibition

Question 20

A student is trying to maximize the rate of a reaction involving the enzyme lactase. Which of the following strategies would be most effective? A) Increase both enzyme and substrate concentraiton while maintaining optimal pH and temperature. B) Add a non-competitive inhibitor to stabilize the active site. C) Increase the temperature as high as possible to increase molecular collisions D) Decrease the pH to 1.0 to make the environemnt more reactive

Answer 20

A) Increase both enzyme and substrate concentration while maintaining optimal pH and temperature. That’s right! Providing more ‘workers’ and more ‘materials’ while keeping conditions perfect ensures the highest possible reaction rate.