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OCR Photosynthesis

Hey all

Just have a few questions on photosynthesis, if anyone could help?

1.How does the wavelength effect the rate of reaction?, Is it just that some light (ie green) is reflected, but others are absorbed. Therefore more photons are absorbed, or am i being stupid?

2.If i was to do this experiment using a photosynthometer, what would i use as a control?

2a. would i need to add more sodium hydrogencarbonate as it get used up?

any help would be appreciated :smile:

Reply 1

Eloades11

Original post by petoid12

Hey all

Hey, usually you have to work this out, which is why you are doing the experiment in the first place. Green light would mainly be reflected because green is the colour of the photosynthetic pigments. Different plants photosynthesise differently, also you have to think about the fact that different antenna complexes absorb specific wavelengths.

Original post by petoid12

2.If i was to do this experiment using a photosynthometer, what would i use as a control?

My control would be the exact same set up, but with no plant, just to make sure that you don't record any photosynthesis occuring. Clearly if there was no plant and photosynthesis was being recorded, then it is not a fair test and there are confounding variables which are not being controlled.

Spoiler

Original post by petoid12

2a. would i need to add more sodium hydrogencarbonate as it get used up?

any help would be appreciated :smile:

I would say no, because then different plants/experiments will get sodium hydrogencarbonate at different times, and this can effect the rate of photosynthesis. As long as they each get the same volume at the start of the experiment that should be fine.

Reply 2

Revd. Mike

Is this ISA/EMPA related?

Reply 3

Eloades11

Original post by Revd. Mike

Is this ISA/EMPA related?

I don't think so, we done a practical at the start of A2 on this sort of thing and it came up in the unit 4 exam(AQA). Although it could be, I hope not, I don't want to encourage cheating :tongue: