IN THE BEGINNING:
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: 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.
WORDS TO KNOW:
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