what molecules cycle between the light dependent and light independent stages of photosynthethis
The molecules that cycle between the light-dependent and light-independent stages of photosynthesis are ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).
During the light-dependent stage of photosynthesis, light energy is used to excite electrons in chlorophyll molecules, which leads to the production of ATP and NADPH. In this stage, water molecules are split, and oxygen is released as a byproduct.
To get ATP during the light-dependent stage, you need to follow these steps:
1. Absorb light energy: Chlorophyll and other pigments in the chloroplasts absorb photons from sunlight.
2. Electron transport chain: Excited electrons from chlorophyll molecules are passed through a series of proteins in the thylakoid membrane, creating a flow of electrons, which generates an electrochemical gradient.
3. ATP synthesis: The electrochemical gradient drives ATP synthase, an enzyme that produces ATP by catalyzing the addition of a phosphate group to ADP (adenosine diphosphate).
NADPH is obtained during the light-dependent stage by the following process:
1. Absorb light energy: Similar to ATP production, chlorophyll and other pigments capture photons and transfer energy to electrons.
2. Electron transport chain: Excited electrons from chlorophyll molecules are again passed through a series of proteins in the thylakoid membrane. This electron flow generates an electrochemical gradient.
3. NADPH synthesis: An enzyme called NADP+ reductase uses the energy from the electron flow to reduce NADP+ (nicotinamide adenine dinucleotide phosphate) to NADPH.
ATP and NADPH produced during the light-dependent stage are then used as energy and reducing power sources in the light-independent stage, also known as the Calvin cycle or the dark reactions. In the Calvin cycle, ATP and NADPH are used to convert carbon dioxide (CO2) into glucose through a series of enzyme-catalyzed reactions. At the end of the Calvin cycle, some molecules regenerate back into ADP and NADP+ to start the cycle again, while others are used to produce glucose and other organic compounds.