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Difficulty: MediumDetermining Control Groups and Baseline Conditions

A student group investigated the enzymatic degradation of cellobiose by cellulase under varying concentrations of a potential heavy-metal inhibitor, cadmium chloride (CdCl2CdCl_2). The cellulase enzyme was dissolved in a 0.05 M0.05\text{ M} citrate buffer solution at pH 4.8\text{pH } 4.8.

Four reaction vessels were prepared as shown in the table below:

Vessel0.05 M0.05\text{ M} Citrate Buffer (mL)Cellobiose Substrate (mL)Cellulase Enzyme (mL)CdCl2CdCl_2 Solution (mL)
14.02.00.00.0
22.02.02.00.0
31.02.02.01.0
40.02.02.02.0

All vessels were incubated at 37∘C37^\circ\text{C} for 30 minutes, and the glucose concentration resulting from cellobiose breakdown was measured.

Based on the experimental design, which vessel served as the baseline control to measure uninhibited enzymatic activity?

  1. A
    Vessel 1
  2. Vessel 2Answer
  3. C
    Vessel 3
  4. D
    Vessel 4

Answer

Vessel 2 served as the baseline control to measure uninhibited enzymatic activity.
Vessel 2 is the baseline control group because it contains both the substrate (cellobiose) and the functional catalyst (cellulase) under identical physical conditions (37∘C37^\circ\text{C}, pH 4.8\text{pH } 4.8), but omits the potential inhibitor (CdCl2CdCl_2). Comparing glucose yields from experimental vessels (Vessels 3 and 4) against Vessel 2 isolates the specific effect of CdCl2CdCl_2 on enzyme activity.

Step-by-Step Solution

1
Identify the purpose of a baseline control group in an inhibition experiment.
A baseline control group must contain all components necessary for the biological reaction (enzyme and substrate) while completely excluding the variable being tested (CdCl2CdCl_2 inhibitor).
This establishes the normal rate of enzyme activity under standard conditions for comparison.
2
Examine the table to find the vessel that includes enzyme and substrate but zero CdCl2CdCl_2.
Vessel 2 contains 2.0 mL cellobiose substrate, 2.0 mL cellulase enzyme, and 0.0 mL CdCl2CdCl_2 solution.
Vessel 2 provides the reference rate for full enzyme function without chemical inhibition.

Key Concept

Determining Control Groups and Baseline Conditions
Estimated Time:1m 0s
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Determining Control Groups and Baseline Conditions

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