Question

Describe their functions
Carbonic Acid --->

BTB Indicator --->

Glucose --->

Control --->

Answer 1

Here are concise descriptions of each item and their typical roles (especially in a classroom/biological experiment context):

- Carbonic acid (H2CO3)
- Forms when CO2 dissolves in water (CO2 + H2O ⇌ H2CO3) and dissociates into H+ and HCO3−.
- Acts as a weak acid and an important buffering species—changes in CO2 shift pH.
- Functionally relevant to respiration/fermentation experiments because CO2 produced by cells increases carbonic acid and lowers pH.

- BTB indicator (bromothymol blue)
- A pH indicator that changes color with pH: yellow in acidic conditions (roughly <6.0), green around neutral (~6.0–7.6), and blue in basic conditions (>~7.6).
- Used to visually report pH changes, commonly to detect CO2-driven acidification (e.g., turns yellow when CO2 increases and pH drops).

- Glucose
- A simple sugar and primary energy source for cells; metabolized via glycolysis and respiration or fermentation to produce ATP, CO2, and other products.
- In experiments it is used as a substrate to stimulate cellular metabolic activity (increasing CO2 production) or as the analyte in biochemical tests (e.g., Benedict’s).

- Control
- The baseline or reference sample in an experiment where the independent variable is not applied (negative control) or where a known response is applied (positive control).
- Purpose is to provide a comparison so you can attribute observed changes to the experimental treatment and rule out confounding factors.

Example link: If you add glucose to a culture, increased respiration produces more CO2 → more carbonic acid forms → pH drops → BTB turns yellow. The control (no glucose or no cells) shows whether that change is due to the added glucose/cells rather than some other factor.