Hill Reaction

The Hill Reaction, used in the 1930s, used Spinacia oleracea to discover that chloroplasts separated from plants containing their thylakoid membranes will still continue to create oxygen, so long as they are given light and an appropriate electron acceptor in place of NADP+. Normally chloroplasts need to use NADP+ as an electron acceptor, but using a centrifuge to separate the chloroplast from the thylakoid membrane, NADP+ is lost.  In our Hill Reaction experiment we chose to compare the effects of using purple light vs. normal light on the effect of photosynthesis. Plants absorb both red and purple light waves, however because purple wavelengths are shorter, they emit a higher frequency and contain more energy (Different Wavelengths of Light Affect on Photosynthesis Rates in Tomato Plants). Light is normally at 600 nm, while purple is at 400 nm and has higher absorbance. Using purple light rather than normal light should mean the absorbance process will take longer. The presence of purple light will cause there to be a higher absorbance level in the chloroplasts in experimental group in comparison to the control group which will have lower absorbance levels exposed to natural light. If correct, then the spectrometer will detect that the solution in the cuvette will reach 0 absorbance at a slower pace than it did with natural light, but not by a large margin. If incorrect, the spectrometer will show the solution reach 0 absorbance at either a quicker pace than our control group or a much more elongated rate.