a). Name the organic molecule being synthesized during the above process b). Whi

Question

a). Name the organic molecule being synthesized during the above process

b). Which tube was the negative control for the experiment

c). Why did you use bromothymol in the experiment

d). what is the purpose of the water filled beaker

e). Name the products of the light independent reaction of photosynthesis

f). Where did the carbon dioxide come from that the Elodea used?

I have a lab test coming up. I would certainly appreciate the help.

Ring stand 1-mL graduated NET Light source pipette 200 Stopper Heat sink (water) Test tube approximately two feet Elodea Figure 9: Set up for carbon fixation experiment. Add 100 ml of distilled water (dH2O) and 50 drops of Bromothymol Blue to the 150-mL beaker. 3. Inflate the balloon and place the opening over the straw. Now, place the strawin your beaker and allow the contents of the balloon to enter your solution. Repeat as necessary until the solution turns yellow. 4. Place one sprig of Elodea into two of the test tubes and carefully pour yellow solution into each until it is almost full 5. Fill a third test tube (without Elodea) with the remaining solution. Note that you may use a different type of test tube stopper depending on availability. 6. Place one test tube with Elodea and the test tube without Elodea in the test tube rack. Cover the second test tube (with Elodea) with aluminum foil and place it in the test tube rack 7. Align the test tube rack and lamp sFo that light falls evenly on all three test tubes. Make sure the heat sink is between the test tube rack and lamp. The light should be approximately two feet from the tube rack (with your heat sink in between). See Figure 9. Note: Your lamp may be slightly different than the one depicted in Figure 9. 8. Note your starting time. utes by holding a white sheet of paper behind the test tub Check the test tubes eve 5 min Test tube with Elodea but not covered Test tube with Elodea with Test tube without Time and covered with foil Elodea fo (minutes) color bubbles Color bubbles color bubbles Clear 60 ON

Explanation / Answer

a) The above experiment is used to demonstrate photosynthesis during which carbon dioxide is fixed to make glucose. Glucose is the organic molecule made during carbon fixation.

b) The controls in this experiment are the tube without elodea (negative control) and the covered tube with elodea (positive control). The purpose of the experiment is to observe carbon fixation and the conditions (light, CO2 and water) needed for it. The elodea plant is what fixes the carbon by the process of photsynthesis. Without carbon fixation the carbonic acid stays in the water and the bromothymol blue remains yellow in colour. In the covered tube, the elodea cannot fix carbon in the absence of light, so the bromothymol solution remains yellow.

So the negative control in this experiment is the tube without elodea.

c) Bromothymol is used as a pH indicator for the presence of CO2. The CO2 from our exhaled air dissolves in the water and forms carbonic acid. This reduces the pH of the water and bromothymol turns yellow. During carbon fixation, the CO2 is used up and as a result the carbonic acid decreases and the pH increases, causing the bromothymol solution to turn back to blue. In the absence of carbon fixation the bromothymol remains yellow as the CO2 dissolved in the water is not used up.

d) The purpose of the water filled beaker is as a heat sink. Light produces heat energy and this could increase the temperature and alter the conditions inside the tubes. The water filled beaker traps the heat and prevents any changes in the conditions of the experiment.

e) Photosynthesis takes place in 2 sequential steps:

light

6CO2 + 6H2O-------------->C6H12O6 + 6O2

That is the products of the light independent reaction are glucose and oxygen. (The oxygen comes from the water).

f) The CO2 came from the air that we blew into the balloon.

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