The Calvin cycle (article) | Photosynthesis | Khan Academy
NADPH and ATP are made in the light stage and are then used in the dark stage (Calvin Cycle) to reduce and fix CO2. jackie4. Add a comment. rameshwar. The relationship between the light-dependent reactions and the Calvin cycle. Before we begin our study of the Calvin cycle, let's look at the. The process of photosynthesis converts light energy to chemical energy, . A layer of cells that comprises most of the interior of the leaf between the upper and In light-independent reactions (the Calvin cycle), carbohydrate molecules are.
These reactions begin with the absorption of light energy by pigments, and end with the production of stored chemical energy in the form of NADPH and ATP. Their stored energy will be used to make sugar from carbon dioxide. The basic relationship between the Calvin cycle and the light-dependent reactions is summarized in Figure 1. The relationship between the light-dependent reactions and the Calvin cycle.
All of the processes of photosynthesis both light-dependent and light-independent reactions occur within the chloroplast.
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By the end of this tutorial you should have a basic working understanding of: The energetics of photosynthesis The basic workings of the Calvin cycle including the fixation, reduction, and regeneration phases Performance objectives: Illustrate the importance of redox reactions in photosynthesis Review that relationship between the light dependent and light independent reactions Describe the inputs and outputs for the light independent reactions Energetics Before we begin our study of the Calvin cycle, let's look at the energetics of sugar synthesis.
We have already studied the catabolism breakdown of glucose during cellular respiration. You know that the process is exergonic and releases about kcal of energy. Remember the first law of thermodynamics? The Calvin cycle is the process by which glucose is made, and it requires all of that energy.
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Where does the energy come from? The light reactions of photosynthesis produce ATP, which provides the Calvin cycle with the necessary energy. In addition, the NADPH produced by the light reactions provides the reducing power to put glucose together. As you should know from studying the Krebs cycle, metabolic cycles involve inputs and outputs, and some molecules are recycled to complete the cycle.
The recycled molecule is ribulose bisphosphate RuBP. Examine figure 2 and locate these molecules in the cycle. Click image to enlarge Calvin's Methods Scientific knowledge is gained through observations and controlled experiments, but how does one study a process that can't be seen directly? About 50 years ago, Melvin Calvin tried to do just that. The study of radioactive elements had become an important new field in chemistry during the war.
Among these newly discovered radioactive elements was carbon On the day in that the Japanese surrendered, a friend and colleague told Calvin, "Now is the time to do something useful with radioactive carbon.
Calvin knew that photosynthesis could only occur in living organisms. Thus, the study of the chemical process was a difficult one.
He devised a method whereby he could raise algae Chlorella pyrenoidosa in a lollipop-shaped disk see Fig. He set up a stream of air that could be controlled.
He could inject radioactive carbon as carbon dioxide into the air stream for a set period of time. Then he would kill the algae with boiling methanol to stop the process of photosynthesis.
Introduction and Learning Objectives
He ran the experiment multiple times, each time killing the algae at different lengths of time after injecting carbon Click image to enlarge Calvin analyzed the dead algae to determine which molecules had incorporated the carbon One G3P molecule leaves the cycle and will go towards making glucose, while five G3Ps must be recycled to regenerate the RuBP acceptor. Regeneration involves a complex series of reactions and requires ATP.
For every three turns of the Calvin cycle, three atoms of carbon are fixed from three molecules of carbon dioxide. In the carbon fixation stage, carbon dioxide is attached to RuBP by the enzyme rubisco.
The resulting 6-carbon product quickly splits into two molecules of a three-carbon compound 3-phosphoglycerate. When three carbon dioxide molecules enter the cycle, six molecules of 3-phosphoglycerate are produced.
What is the relationship between light reactions and the Calvin cycle? | Yahoo Answers
In the reduction stage, each 3-phosphoglycerate first gains a phosphate group from an ATP molecule which is converted to ADP. The net result of this process is conversion of a 3-phosphoglycerate molecule into a molecule of the three-carbon sugar glyceraldehyde 3-phosphate G3P.
For every three turns, one molecule of G3P exits the cycle and goes towards making glucose. Two G3Ps can combine to make one glucose, so one G3P can be thought of as "half" a glucose molecule.