Figure 1 shows the reaction rate of Enzyme Z at different temperatures, while Figure 2 shows the reaction rate of Enzyme Z at different substrate concentrations (at a constant optimal temperature).
[Figure 1: Line graph. X-axis: Temperature (°C) from 0 to 80. Y-axis: Reaction Rate. The curve peaks at 40°C, then drops sharply.
Figure 2: Line graph. X-axis: Substrate Concentration (mM) from 0 to 10. Y-axis: Reaction Rate. The curve increases steeply, then plateaus after 6mM.]
Based on both figures, which of the following conditions would result in the highest reaction rate for Enzyme Z?
Correct: D
To achieve the highest reaction rate, both temperature and substrate concentration should be near their optimal levels.
- From Figure 1, the optimal temperature for Enzyme Z is 40°C, where the reaction rate peaks. Rates are lower at 20°C and significantly lower at 50°C (due to denaturation).
- From Figure 2, the reaction rate continues to increase with substrate concentration until it plateaus around 6 mM, indicating that 6 mM or higher concentrations are optimal/saturating.
Let's evaluate the choices:
- A: 20°C (sub-optimal temp), 2 mM (sub-optimal conc) -> Low rate.
- B: 40°C (optimal temp), 4 mM (sub-optimal conc, below saturation) -> Moderate rate.
- C: 50°C (denaturing temp), 8 mM (optimal conc) -> Low rate due to temperature.
- D: 40°C (optimal temp), 8 mM (optimal/saturating conc) -> Highest possible rate.
Therefore, 40°C and 8 mM substrate concentration would result in the highest reaction rate.