A. The Induced Fit model takes into account the three-dimensional structure of enzymes and substrates, including the precise bond angles and lengths that occur upon substrate binding.
B. The Lock and Key model accurately represents the conformational changes that occur in enzymes when a substrate binds.
C. The Induced Fit model emphasizes the specificity of the enzyme-substrate interaction based on the complementary nature of their shapes.
D. The Lock and Key model fails to account for the dynamic nature of enzymes and their ability to adapt to the substrate.
4. Which of the following statements best explains the relationship between enzymes and the activation energy of a reaction?
A. Enzymes lower the activation energy required to break bonds within the substrate.
B. Enzymes increase the activation energy required to break bonds within the substrate.
C. Bonds in the enzyme are broken thus increasing the activation energy.
D. Enzymes directly provide the energy required to break bonds within the substrate.
Q5-6: A student carried out an experiment to investigate the effect of changing the substrate concentration on the activity of an enzyme. Their data is shown in the graph below:
5. At which concentration are approximately half of the active sites of the enzyme filled at a given time?
A. K
B. L
C. M
D. N
6. Why does the graph begin to flatten off at M?
A. The enzyme becomes denatured
B. An inhibitor is present
C. There are fewer active sites available for the substrate molecules
D. The enzyme concentration is high
7. The blue dotted line shows the uninhibited reaction of an enzyme. If a competitive inhibitor of an enzyme is added, which line would most accurately represent the enzyme activity?
8. Which of the following is an example of an intracellular enzyme-catalysed reaction?
A. Saprotrophic breakdown of dead matter
B. Lysosomal breakdown of proteins by proteases
C. Acetylcholinesterase in synaptic cleft
D. Pancreatic trypsin in digestion
9. Which of the following statements accurately describes the pathway which produces isoleucine from threonine?
I. The pathway is an example of end-point inhibition
II. As isoleucine levels increase, it binds to the active site of threonine deaminase, inhibiting the activity of this enzyme.
III. If isoleucine is not used up, the pathway prevents build-up of intermediate molecules
A. I only
B. I and II only
C. I and III only
D. I, II, and III
10. Which of the following statements are correct for mechanism-based inhibition using penicillin as an example?
I. The irreversible binding of penicillin to DD transpeptidase is through ionic bonding
II. The chemical changes induced by the binding of penicillin to DD transpeptidase prevents the formation of peptidoglycan cross-links in bacterial cell walls
III. Gene mutations which cause active site conformational change in DD transpeptidase can lead to bacterial resistance to penicillin
