Question 1
Multiple choiceMedium1 markA purified enzyme forms a complex with each of four substrates. Shape-change scores compare each molecule’s shape in the complex with its unbound shape; 0 means no change, and a positive score means a change.
| Substrate | Enzyme shape-change score | Substrate shape-change score |
|---|---|---|
| P | 2 | 1 |
| Q | 2 | 0 |
| R | 0 | 1 |
| S | 0 | 0 |
Which substrate’s results are consistent with induced-fit binding?
Show answer and explanation
Answer: A. Induced-fit binding involves a change in shape of both the enzyme and the substrate. For P, both shape-change scores are positive, so both molecules change shape during complex formation.
B: uses the enzyme’s positive score but overlooks that the substrate’s score is zero.
C: uses the substrate’s positive score but overlooks that the enzyme’s score is zero.
D: shows no shape change in either molecule and therefore is not induced-fit binding.
Remember: induced-fit binding involves shape changes in both interacting molecules.