Determining Control Groups and Baseline Conditions

A team of biomedical researchers investigated the inhibitory effect of a plant-derived polyphenol, compound CP, on bacterial biofilm formation by *Pseudomonas aeruginosa* on silicone catheter surfaces. The researchers prepared four different culture setups in microtiter plate wells and measured biofilm mass after incubation at $37^\circ\text{C}$ for 24 hours:

- Setup I: Silicone catheter disc + nutrient broth + *P. aeruginosa* + $0\text{ }\mu\text{g/mL}$ compound CP (vehicle solvent only)
- Setup II: Silicone catheter disc + nutrient broth + *P. aeruginosa* + $50\text{ }\mu\text{g/mL}$ compound CP
- Setup III: Silicone catheter disc + nutrient broth (no bacteria added) + $0\text{ }\mu\text{g/mL}$ compound CP
- Setup IV: Nutrient broth only (no catheter disc, no bacteria added)

Based on the experimental design, match each culture setup (Setups I–IV) to its specific experimental role or baseline function.

A student group investigated the enzymatic degradation of cellobiose by cellulase under varying concentrations of a potential heavy-metal inhibitor, cadmium chloride ($CdCl_2$). The cellulase enzyme was dissolved in a $0.05\text{ M}$ citrate buffer solution at $\text{pH } 4.8$.

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

All vessels were incubated at $37^\circ\text{C}$ 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?

Students performed an experiment to study the effects of different metal oxide catalysts on the rate of decomposition of hydrogen peroxide ($H_2O_2$) into water ($H_2O$) and oxygen gas ($O_2$). In each of 4 trials, the students added $5\text{ mL}$ of a $3\%$ $H_2O_2$ solution to a test tube at $25^\circ\text{C}$ containing either a specific catalyst or no catalyst. They measured the total volume of $O_2$ gas produced in milliliters ($\text{mL}$) over a period of 5 minutes. The experimental setups are summarized in the table below:

To determine the baseline rate of hydrogen peroxide decomposition in the absence of any catalyst, the students should refer to the results of which trial?