Please help me answer the following questons from this chart exercist-electron t

Question

Please help me answer the following questons from this chart exercist-electron transport in Chloroplasts

Describe the purpose of each test tube used in this experiment:

Tube 1:

Tube 2:

Tube 3:

Tube 4:

2. In which test tube(s) was photosynthesis occuring, and how do you know?

Side note: For test tube 1 i put: Tube one didn't have DCPIP which becomes colorless during photosynthesis so even if photosynthesis happened we couldnt tell. I think it did because it has the right enviorment.

for test tube 2 I put: Test tube two had the right enviorment but not as much water so it didnt undergo as much photosynthesis as 1

for question 2: I think that tests tubes one and two underwaent phtosynthesis but i cant explain since im getting electron transport chain confused with photosynthesis part even though they go hand in hand.

Thanks in advance

Tube chloroplast PO4 Buffer Water DCPIP 1 1.5ml 3ml 1.5ml 0 2 1.5ml 3ml 0.5ml 1ml 3 0 3ml 2.0ml 1ml 4 1.5ml 3ml 0.5ml 1ml

Explanation / Answer

The answer is that the test tubes are measured for their light transmittance in a spectrophotometer and the dye reduction and the transmittace of light increase can be measure using the dye, 2,6-dichlorophenolindophenol (DCPIP or DPIP) . When oxidized, DCPIP is blue with a maximal absorption at 600 nm; when reduced, DCPIP is colorless.DCPIP can be used to measure the rate of photosynthesis.As DCPIP is reduced and becomes colorless, the resultant increase in light transmittance (not absoprtion of light) can be measured using a spectrophotometer.

Tube 1:For test tube 1 i put: Tube one didn't have DCPIP which becomes colorless during photosynthesis so even if photosynthesis happened we couldnt tell. this holds true if given a colorless to naked eye. However if you measure the transmittance of light or inverse of absorption of light at 600 nm the value will be the control value for all other tubes.

Tube 3: will be a negative control where the chloroplast are not present and the dye will give wavelenght measure ment at 600 nm. this measurement will be blue in color and a negative control.no chloroplast and hence no photosysynthesis and hence all blue color.

Tube 2,4, will have the chloroplast and the DCPIP and all the reduction. both should give same transmitance in a spectrophotmeter.

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