PHOTOSYNTHESIS the process of light energy to chemical energy

Photosynthesis-the process by which plants and other organisms make food. It is a chemical process that uses sunlight to turn carbon dioxide into sugars the cell can use as energy.


light dependent reaction

Phase One: As light enters the light dependent reaction in the thykaloid membrane of a chloroplast it is converted into ATP (chemical energy) and NADPH. As the energy excites the electrons in photosystem II, a water molecule is split which releases a hydrogen molecule into the system, hydrogen into the thylakoid, and oxygen then becomes a waste product.

Step 1: The light energy excites electrons in photosystem II. The light energy then causes a water molecule to split, releasing an electron into the electron transport system, a hydrogen ion (proton) into the thylakoid space, and oxygen a waste product.

Step 2: The excited electrons move from photosystem II to an electron-acceptor molecule in the thylakoid membrane

Step 3: The electron-acceptor molecule tranfers electrons along a series of electron-carriers to photosystem I

Step 4: In light, photosystem I transfers electrons to a protein (ferrodoxin). The electrons lost by photosystem I are replaced by electrons from photosystem II

Step 5: Lastly, ferrodoxin transfers the electrons to the electron carrier NADP+, forming storage molecule NADPH

Phase two: The Calvin Cycle

Phase two: Light-independent reactions do not use light as a reactant so they can take place day or night, they require the products of the light-dependent reactions to function. The light-independent molecules depend on the energy carrier molecules, ATP and NADPH, to drive the construction of new carbohydrate molecules for energy. After the energy is transferred, the energy carrier molecules return to the light-dependent reactions to make more energized electrons.

Step 1: In carbon fixation, carbon dioxide molecules combine with carbon compounds to form carbon molecules called phosphoglycerate. The joining of carbon dioxide with other organic molecules is called carbon fixation.

Step 2: The chemical energy stored in ATP and NADPH is transferred to the GPA molecules to form high-energy molecules called glyceraldehyde phosphates. ATP supplies the phosphate groups for forming G3P molecules, while NADPH supplies hydrogen ions and electrons.

Step 3: G3P molecules leave the cycle to be used for the production of glucose and other organic compounds.

Step 4: An enzyme called rubisco converts the remaining G3P molecules into carbon molecules called ribulose 1. These molecules combine with new carbon dioxide molecules to continue the cycle.


energy-the ability to do work

thermodynamics-the study of the flow and transformation of energy in the universe

metabolism-all the chemical reactions in a cell

photosynthesis-anabolic pathway in which light energy from the sun is converted to chemical energy for use by the cell

adenosine triphosphate (ATP)-most important biological molecule that provides chemical energy.

thylakoids-flattened saclike membranes that are arranged in stacks called granum.

stroma-the fluid-filled space that surrounds the grana

pigments-light-absorbing colored molecules

calvin cycle-second phase in photosynthesis in which energy is stored in organic molecules such as glucose


Created with images by gr33n3gg - "Sun" • ab9kt - "leaf" • werner22brigitte - "scouring rush horsetail plant nature" • momentcaptured1 - "palm plant 2010 041" • LoggaWiggler - "mammoth sheet gunnera manicata giant rhubarb" • beeki-thecoffeedrinker - "teichplanze pond horsetail"

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