I might just pull an all-nighter?

Question

Bio. Can anyone help me with this question:

Phenol red is a chemical that turns red when carbon dioxide, CO2, is absent and yellow when CO2 is present. A small green plant seedling is placed in phenol red in the dark. Which one of the following is most likely to occur?


Answer: If the solution is red to begin with, it will turn yellow because respiration is occurring.

I don't understand why that is the answer.

Answer 1

OK. During daytime, the plant uses sunlight to make glucose in a process we all know as photosynthesis. CO2 is used in this process and O2 is a waste product. At night, when there is no light, the plant does not perform photosynthesis, but does perform respiration. In order for the mitochondrion to change the glucose to ATP, the plant takes in O2. The waste product in this case, is CO2.

Answer 2

I agree with Billy.

The difference between animal and plant cells is that plants can also convert CO2 and sunlight into glucose to store energy, whereas animal cells need to get the glucose from an outside source (by eating plants or other animals).

Plant cells need to metabolize sugar into CO2 to obtain energy, just like animal and bacterial cells. In the process they take in O2 and release CO2, just as an animal cell would. Under normal conditions, though, they take in more CO2 than they produce (since the carbon is incorporated into the plant's structure, allowing it to grow). The result is a *net* decrease in CO2 and an increase in O2 in the air.

If you take away sunlight, the plant loses its ability to turn CO2 into sugar, so the CO2 from metabolism will build up, turning the phenol solution yellow.

Answer 3

Plants change CO2 to O2, so if the solution is red (absent of CO2) once the seedling is introduced, CO2 will be introduced, (because the plant has unprocessed CO2 still in it), turning the Phenol yellow.

Answer 4

ooo...good luck girly! I just had a lab practical with biochemical testing!