Which one the following events occurs during Calvin cycle reactions?

Answer 1

This is a copy of my answer to a similar question: The problem Calvin was investigating was how did the carbon in carbon dioxide get converted into the carbon in carbohydrates during phototsynthesis. This meant he had to find a way of tracing the path of the carbon as it was built up into carbohydrate: CO2 ---> substance A ---> substance B ---> etc ---> CH2O (carbohydrate) Calvin discovered the 'Calvin cycle' by choosing a suitable organism to work with, devising a clever piece of apparatus and applying two carefully-chosen techniques. The organism was a single-celled alga called Chlorella. Each cell contains a single, large chloroplast. Because it is single-celled, it can absorb carbon dioxide rapidly and can be killed rapidly, making handling easier than it would be if a larger plant had been used. The apparatus was a flat glass flask called the 'lollipop' apparatus after its shape. The flat shape meant that all of the Chlorella cells inside could receive the maximum amount of light, and so carry out the maximum amount of photosynthesis. With a spherical flask, cells in the middle would receive less light than cells at the outside, and so would photosynthesise less. The first technique he used was to track the path of carbon during photosynthesis by using a radioactive isotope, 14C. This had only recently become available in the 1940's. The advantage of using a radioactive isotope is that it was possible to detect the presence of small amounts of labelled carbon. Calvin added radioactive carbon dioxide to the culture solution containing the Chlorella cells and, after a short time, emptied the cells into a container of alcohol. The alcohol rapidly killed the cells, stopped any further reactions and started to extract the chemicals from them. By varying the time for which the cells were exposed to the radioactive carbon, CAlvin could work out the sequence of chemical reactions through which the carbon was passing. The second technique was two-dimensional paper chromatography. Chromatography is a method for separating mixtures of compounds. A mixture is added as a small spot near the base of a strip of paper. If the paper is dipped in a solvent, it will travel up the paper carrying the mixture with it. However, different substances will be carried different distances, and so the mixture will be separated. After carrying out one separation, Calvin turned the paper through 90o and carried out a second separation using a different solvent (hence the name two-dimensional). This gave a better separation of similar compounds. Having separated the substances which he had extracted from the cells, Calvin then had to find where they were on the chromatography paper! He could not see them because they were colourless. To locate the substances containing the radioactive carbon, he placed a piece of photographic film on top of the paper. The radiation given off by the 14C made the film go dark, so he could then locate where they were on the paper. This technique is called autoradiography. The final step was to identify the compounds containing the 14C. This took about 10 years! At the end, he was able to describe the sequence of compounds through which the carbon passed as it was converted from carbon dioxide to carbohydrate. He discovered that it was in fact a cycle of reactions, hence the name 'Calvin cycle'. He was awarded the 1961 Nobel Prize in Chemistry for this work. For further information see: http://en.wikipedia.org/wiki/Calvin_cycle http://en.wikipedia.org/wiki/Melvin_Calvin http://nobelprize.org/nobel_prizes/chemistry/laureates/1961/calvin-lecture.html

Answer 2

Calvin-Benson cycle:

1. carbon fixation
2. synthesis of G3P
3. regeneration of RuBP

Answer 3

Carbohydrates are produced in this cycle. There is no production of energized electrons, ATP or of the enzyme helper NADPH.