Post-Lab Report #6 Lab Topic 6: Enzymes (10 points possible) 1. If a substrate molecule is abundant in a reaction, what should happen to the reaction rate when more associated enzyme molecules are a

Post-Lab Report #6

Lab Topic 6: Enzymes (10 points possible)

1. If a substrate molecule is abundant in a reaction, what should happen to the reaction rate when more associated enzyme molecules are added to the reaction? (1 point)

2. If the number of enzyme molecules in a reaction is constant and the number of associated substrate molecules is low, what do you expect to happen to the reaction rate when more substrate molecules are added to the reaction? (1 point)

3. Identify two physical factors (from among those discussed in the lab manual) that can have an effect on an enzyme, and briefly describe how each factor can do so. (2 points)

4. For the enzyme reaction in Exercise 6.2 in the lab manual (where Catechol (colorless substrate) is converted to Benzoquinone (reddish-brown product)) a spectrophotometer is used to measure the absorption levels of the samples as they turn darker over time. You will notice (in small print) on the diagram of the spectrophotometer (lab manual Figure 6.8) that the apparatus can measure either absorption or transmittance depending on the setting that is chosen. If you were to select absorption to monitor the samples (how much light they absorb) over time, how would you expect the absorption numbers (values) to change as the reaction in the Tube 1 (from lab manual Table 6.1) proceeded? In other words, would you expect the absorption numbers to increase or decrease over time, and why? (1 point)

5. Of the three tubes listed in Table 6.1 in the lab manual, which tube should change color (darken) the fastest, and why? (1 point)

6. What kind of reaction (color change) should you expect to see in Tube 3 from Table 6.1, and why? (1 point)

7. Briefly explain why lemon juice (which has a pH of about 3) when sprayed on freshly cut fruit, will keep the fruit from turning brown. (1 point)

8. A freshly cut raw potato turns brown quickly when exposed to oxygen in the air. Briefly explain why cooked mashed potatoes stay white and do not turn brown like the raw potato does? (1 point)

9. Briefly explain how an enzyme is ultimately affected by the reaction that it catalyzes. (1 point)