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Plant pigments absorb some wavelengths but reflect green wavelengths. Mel Curtis/Digital Vision/Getty Images All the food that people eat and all the fossil fuels that people use comes from photosynthesis. Plants and other organisms that carry out photosynthesis obtain carbon dioxide, water and light and carry out chemical reactions to produce sugar and oxygen. This process effectively converts energy from sunlight into chemical forms of energy that other biological organisms can use.
Light Absorption
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Pigments refer to molecules that absorb light. They usually absorb some wavelengths of light and reflect others. The pigment in plants, known as chlorophyll, mainly absorbs violet-blue and reddish orange-red wavelengths and also a little green-yellow-orange wavelengths. Chlorophyll does not absorb green, it reflects it, making plants appear green. Plants use the light energy they absorb to trigger photosynthetic chemical reactions.
Light-Dependent Reactions
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The first stage of photosynthesis consists of light-dependent reactions. During this stage, plants use the energy from the light that chlorophyll absorbs to carry out chemical reactions. They turn water absorbed by the roots into oxygen and energy carrier molecules that are known as ATP and NADPH.
Light-Independent Reactions
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Known as light-independent reactions or dark reactions, the second stage of photosynthesis can occur in the dark if the plant already has the energy carrier molecules. However, according to the Estrella Mountain Community College website, new evidence suggests that these reactions require indirect stimulation from light. In these reactions, plants convert the carbon dioxide they obtain from the air into glucose. In these light-independent reactions, plants convert six molecules of carbon dioxide into one molecule of glucose.
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