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The light-dependent reactions convert light energy into chemical energy. The goal of the light-dependent reactions of photosynthesis is to collect energy from the sun and break down water molecules to produce ATP and NADPH.
- Glossary
Photosynthesis Reactions; Glossary; Evolution. Evolution...
- Leaf Structures
When it comes to photosynthesis, the most important parts of...
- Reactants and Products
The light-independent reactions of photosynthesis—also known...
- Mechanisms of Evolution
The change in peppered moths’ coloration from light to dark,...
- Glossary
- Step 1: Excitation of Photosystems with Light Energy and Photolysis of Water
- Step 2: Generation of ATP by Electron Transport Chain
- Step 3: Formation of NADPH
- Alternative Pathway
- Chemical Equation
- Fate of The Products
The function of the light-dependent reaction is to convert light energy into chemical energy within a multi-protein complex called the photosystem, found in the thylakoid membranes. There are two types of photosystems found in most plants: photosystem I (PSI) and photosystem II (PSII). Each photosystem is made of two components: 1) antenna complex ...
The electrons released from photosystem II enter a chain of proteins known as electron transport chain (ETC). They move from PSII to a small lipid-soluble molecule, plastoquinone (Pq), and then to a protein complex called cytochrome b6f. The electrons are finally transferred to a copper-containing protein called plastocyanin (Pc) before being accep...
This stage is the final step of the light-dependent reaction during which high energy electrons released from PSI travel a short second leg of the electron transport chain. Here, the electrons are first transferred to an iron-containing protein called ferredoxin (Fd) and then to a reducing agent, NADP, to form NADPH. This type of electron transport...
Sometimes plants follow an alternative path of electron transport called cyclic photophosphorylation. This term is named so because electrons released from PSI move along a circular path before returning to the same photosystem. Cyclic photophosphorylation does not involve PSII and produces only the ATP, stopping the production of NADPH.
2H2O + 2NADP+ + 3ADP + 3Pi → O2+ 2NADPH + 3ATP Reactants 1. H2O 2. NADP 3. ADP + Pi End Products 1. O2 2. NADPH 3. ATP
The energy-carrier molecules, ATP, and NADPH produced in the light reaction are used in the second phase of photosynthesis or the Calvin cycle to assemble sugar molecules.
Photosynthesis takes place in two stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, which take place at the thylakoid membrane, chlorophyll absorbs energy from sunlight and then converts it into chemical energy with the use of water.
Key Points. Light energy splits water and extracts electrons in photosystem II (PSII); then electrons are moved from PSII to cytochrome b6f to photosystem I (PSI) and reduce in energy. Electrons are re-energized in PSI and those high energy electrons reduce NADP + to NADPH.
Photosynthesis takes place in two sequential stages: the light-dependent reactions and the light independent-reactions (Calvin cycle). In the light-dependent reactions , energy from sunlight is absorbed by chlorophyll and that energy is converted into stored chemical energy.
The light-dependent reactions generate the high energy intermediates ATP and NADPH for carbon fixation and the light-independent reactions recycle the ADP and NADP + to send back to the light-dependent reactions.
In the light-dependent reactions of photosynthesis, the energy from light propels the electrons from a photosystem into a high-energy state. In plants, there are two photosystems, aptly named Photosystem I and Photosystem II, located in the thylakoid membrane of the chloroplast.
