Elodea is a type of aquatic plant that is often used in lab settings, particularly in biology classes, to demonstrate photosynthesis and cellular respiration. Bromothymol blue (BTB) is a chemical indicator that is often used in conjunction with elodea to demonstrate these processes. When BTB is added to a solution containing elodea, it can change color depending on the concentration of carbon dioxide (CO2) and hydrogen ions (H+) present in the solution. This allows students to observe and measure the effects of photosynthesis and cellular respiration on the concentration of these substances.
During photosynthesis, elodea absorbs CO2 from the air and uses it, along with light energy, to synthesize glucose. The glucose is then used by the plant as an energy source during cellular respiration. During cellular respiration, elodea breaks down the glucose to release energy, which it uses to perform various functions. This process also produces CO2 and H+ as byproducts.
When BTB is added to a solution containing elodea, it changes color based on the concentration of CO2 and H+ present in the solution. If the concentration of CO2 is high and the concentration of H+ is low, the BTB will turn yellow. If the concentration of CO2 is low and the concentration of H+ is high, the BTB will turn blue. If the concentrations of CO2 and H+ are balanced, the BTB will remain green.
In a lab setting, students can observe the effects of photosynthesis and cellular respiration on the concentration of CO2 and H+ in a solution containing elodea and BTB. By shining a light on the elodea or adding a source of glucose, students can stimulate photosynthesis and observe the resulting increase in the concentration of CO2 and decrease in the concentration of H+. Similarly, by depriving the elodea of light or removing the source of glucose, students can stimulate cellular respiration and observe the resulting decrease in the concentration of CO2 and increase in the concentration of H+.
Overall, the elodea and BTB lab is a useful tool for demonstrating the processes of photosynthesis and cellular respiration and for allowing students to observe and measure the effects of these processes on the concentration of CO2 and H+ in a solution.