Enzyme Practice Test

Pyruvate kinase, a key enzyme in the glycolysis pathway, is inhibited by the amino acid alanine. The ability of alanine to inhibit the enzyme is not affected by increasing the concentration of substrate. Which of the following best explains the mechanism by which alanine inhibits pyruvate kinase activity?

• Alanine binds to an allosteric site of the enzyme, changing the shape of the enzyme’s active site.

• Alanine increases the enzyme-substrate binding until the enzyme becomes saturated.

• Alanine is a competitive inhibitor that reversibly binds to the active site of the enzyme.

• Alanine binds to the substrate, preventing the substrate from being able to bind to the active site of the enzyme.

Tags

NGSS.HS-PS1-2

Which of the following correctly describes how enzymes work?  

• they lower the energy of the reactants to increase the rxn rate
• they supply energy to the reaction to increase the rxn rate
• they lower the energy of the products to increase the rxn rate
• they lower the activation energy of the reaction to increase the rxn rate

Tags

NGSS.HS-PS1-5

The energy needed to start a reaction

• activation energy
• adhesion energy
• chemical energy
• cohesion energy

Tags

NGSS.HS-PS1-4

Which of these is NOT true?

• Enzymes can denature (change shape) when the temperature gets too high.
• Enzymes can only be used once in a chemical reaction. 
• Extreme pH can denature enzymes.
• Enzymes speed up chemical reactions. 

Tags

NGSS.HS-PS1-5

Blocking Active site of an enzyme

• competitive inhibition
• allosteric inhibition

Some bacteria are metabolically active in hot springs because ____________

• their enzymes are insensitive to temperature
• they use molecules other than proteins as their main catalysts
• their enzymes have high optimal temperatures
• they are able to maintain an internal temperature much cooler than that of the surrounding water

Tags

NGSS.HS-LS4-4

How do enzymes affect chemical reactions?

• Increased activation energy
• Decreased activation energy
• Increased energy change
• Decreased energy change

Enzymes with their highest activity at an alkaline (basic) pH are represented by which of the following graphs?

• I only

• II only

• III only

• I and III only

Graphs representing enzymes sensitive to changes in pH include which of the following?

• I only

• IV only

• I, II, and III only

• III and IV only

The most likely explanation for the results shown in Graph I is that

• pH affects the shape of the active site of the enzyme

• pH affects the temperature of the reaction

• the enzyme has a quaternary structure

• the enzyme has disulfide bonds