The Hill Reaction Lab, Help?Why were all cuvettes kept in the dark except for the 2 min time period in which the transmittance measurement was taken with the spectrophotometer?    2.What does the...

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bandmanjoe | Middle School Teacher | (Level 2) Senior Educator

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All the cuvettes were kept in the dark except for the exposure time to insure no light would initiate the photosynthesis reaction, which involves the electron transport chain.  The color indicator would have changed from a deep blue color to a relatively colorless hue, indicating an excess of electrons produced by the electron transport chain.  Exposure to light stimulates the chloroplasts, the organelles containing chlorophyll, to produce a simple sugar, glucose, from carbon dioxide from the atmosphere and water from the ground.  This is accomplished by the use of electron flow across the membranes of the chloroplast, breaking the old bonds of the carbon dioxide and water and creating new ones between the glucose and oxygen that is produced as a waste product.  The evidence provided by this lab clearly indicates that photosynthesis is fueled by the electon transport chain, indicated by the color change in the color indicator.

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