5. Students performed a lab in biology to look at the relationship between photo

Question

5. Students performed a lab in biology to look at the relationship between photosynthesis and cellular respiration. They filled flasks with equal amounts of water. They added the indicator bromthymol blue (blue in base, yellow in acid) to each flask. Then a sprig of elodea was placed into each of two flasks containing bromthymol blue. One flask was left in the dark, the other in the light for 24 hours. The bromthymol blue in the flask in the dark turned yellow. The other remained blue. Explain these results.

Explanation / Answer

The flask with bromothymol blue,a spring of elodea and kept in dark :

* it explains cellular respiration ( absence of photosynthesis in dark).

* one of the products of cellular respiration is carbon dioxide. when it is released into water, the water turns to acidic PH around 5.5, acidic, . So bromothymol blue changes its colour to yellow.

The flask with bromothymol blue,a spring of elodea and kept in light :

* it explains cellular respiration and photosynthesis.

the carbon dioxide released in cellular respiration is utilised for photosynthesis. hence there is no change in colour of bromothymol blue.

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