It stores energy from sunlight into the long-term storage form of sugar, which can be used by plants, or eaten by animals to form the basis for the food chain.Ĭ. It turns carbon dioxide from the air into carbon that living things can use to make sugars, proteins, nucleotides, and lipids.ī. Why is the Calvin cycle important to most ecosystems?Ī. Photosynthesis – The process by which living things capture energy from sunlight and use it to make fuel and organic materials to build their cells.ġ.Energy Pyramid – A diagram that illustrates the flow of energy through an ecosystem.Chloroplast – The organelle in plant cells where energy from sunlight is turned into ATP and sugar.This means that to produce a single molecule of glucose, 18 ATP and 12 NADPH are consumed. It takes three turns of the Calvin cycle to create one molecule of glyceraldehyde-3 phosphate.Īfter six turns of the Calvin cycle, two molecules of glyceraldehyde-3 phosphate can be combined to make a glucose molecule.Įach turn of the Calvin cycle also uses up 3 ATP and 2 NADPH in the processes of reducing (adding electrons to) 3-phosphoglyceric acid to produce glyceraldehyde-3 phosphate, and regenerating RuBP so that they can accept a new atom of carbon from CO2 from the air. Calvin Cycle DiagramĮach turn of the Calvin cycle “fixes” one molecule of carbon that can be used to make sugar. The sixth exits the cycle to become one half of a glucose molecule. To accomplish this equation, five out of six glyceraldehyde-3 phosphate molecules that are created through the Calvin cycle are regenerated to form RuBP molecules. ![]() It is a complex process involving many steps.īecause it takes six carbon molecules to make a glucose, this cycle must be repeated six times to make a single molecule of glucose. Some glyceraldehyde-3 phosphate molecules go to make glucose, while others must be recycled to regenerate the five-carbon RuBP compound that is used to accept new carbon molecules. In chemistry, the process of donating electrons is called “reduction,” while the process of taking electrons is called “oxidation.” Regeneration This step is called “reduction” because NADPH donates electrons to the 3-phosphoglyceric acid molecules to create glyceraldehyde-3 phosphate. The energy from the ATP and NADPH is transferred to the sugars. In this way, the Calvin cycle becomes the way in which plants convert energy from sunlight into long-term storage molecules, such as sugars. This stage uses energy from ATP and NADPH created in the light-dependent reactions of photosynthesis. In the second stage of the Calvin cycle, the 3-PGA molecules created through carbon fixation are converted into molecules of a simple sugar – glyceraldehyde-3 phosphate (G3P). Due to the key role it plays in photosynthesis, RuBisCo is probably the most abundant enzyme on Earth. This reaction is catalyzed by the enzyme RuBP carboxylase/oxygenase, also known as RuBisCO. ![]() The resulting six-carbon compound is then split into two molecules of the three-carbon compound, 3-phosphoglyceric acid (3-PGA). In carbon fixation, a CO 2 molecule from the atmosphere combines with a five-carbon acceptor molecule called ribulose-1,5-bisphosphate (RuBP). We will discuss how the Calvin cycle creates simple sugars from CO 2 below. Scientists have raised concerns because, in addition to putting huge amounts of CO 2 back into the air by burning coal, oil, and gasoline, humans have also cut down about half of all Earth’s forests, which play an important role in removing CO 2 from the air. The Calvin cycle also regulates the levels of carbon dioxide, a greenhouse gas, in the Earth’s atmosphere. The carbon backbones created in the Calvin cycle are also used by plants and animals to make proteins, nucleic acids, lipids, and all the other building blocks of life.
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