describe the process of Photosynthesis. Flashcards
1) Light dependent stage
water is split into oxygen and hydrogen.
Light splits the water (photolysis) in order to do what?
in order to obtain the hydrogen atoms for the light-
independent stage.
What is light energy trapped by
by the chlorophyll. This takes place on the thylakoid membranes.
The job of the light stage is to
split H 2 O to produce hydrogen atoms for the light- independent stage.
(photo – light, lysis- splitting)
2H 2 O 4H + O 2
2) What happens in the light-independent stage?
the hydrogen from the light-dependent stage, combines with carbon dioxide to form glucose.
The light independent stage is a what reaction?
reduction reaction
What isnt needed in the light independent stage
neither chlorophyll or light energy
where does the light independent stage take place
in the stroma of the chloroplast
Overall reaction: 6CO 2 + 6H 2 O ——-> C 6 H 12 O 6 + 6O 2
experiment
Carbon dioxide contains oxygen and carbon. There is a rare isotope of oxygen whose atoms are slightly heavier than those of normal oxygen and can be detected by a mass spectrometer. An experiment was done where a plant was exposed to CO 2 , whose O has been radioactively labelled, and allowed to photosynthesize.
The heavy oxygen gets in the carbohydrates which the plant makes, which shows the oxygen in the carbohydrates made by plants comes from the CO 2 . Hydrogen in the carbohydrates comes from the water (H 2 O), which was split by sunlight. If CO2 with radioactive C is used, the radioactive C is found in carbohydrates, so C in carbohydrates
come from the CO2.
Does photosynthesis occur in the night?
Yes, photosynthesis can occur in the night, once
enough hydrogen remains from the light-dependent stage to be used in the light-dependent stage to reduce the carbon dioxide.
