Light-Dependent-Reaction

  • Renewable Energy Source: Light is a renewable energy source; Sun is the primary source of light energy on Earth.

  • Photosynthesis in Plants: Plants use all colors of light except green, which makes them appear green due to the reflect.

  • Photosynthesis Inquiry: Focus on how light-dependent reactions occur during photosynthesis.

  • Photosynthesis Overview:

    • Converts solar energy to chemical energy.

    • Occurs in chloroplasts.

    • Involves autotrophs.

  • Photosynthetic Pathway:

    • Reactants: Carbon dioxide and water.

    • Light energy input produces sugar (glucose) and oxygen.

  • Photosynthesis Inquiry: Investigation of light-dependent reactions in photosynthesis.

  • Light-Dependent Reactions: These occur only when solar energy is available.

  • Energy Capture: Pigment molecules capture energy from photons and store it in ATP and NADPH.

  • Water Splitting: Chlorophyll replaces lost electrons from splitting water, producing O2.

  • Oxygen Production: Splitting of water molecules yields oxygen as a waste product.

  • Electron Movement Inquiry: Focus on ATP production during light reactions.

  • Electron Flow Mechanism: Light strikes P680 and P700, resulting in electron flow that produces ATP and NADPH.

  • Process Overview: Light excites P680 in PSII, leading to proton pumping and ATP synthase rotation.

  • Electron Ejection: Excited electrons are ejected from chlorophyll and enter the first protein in the electron transport chain.

  • Water Contribution: Water donates electrons to replace ejected ones, splitting into O2 and H+.

  • Proton Pumping: Electron movement pumps protons into the thylakoid lumen, creating a concentration gradient.

  • ATP Production: Proton diffusion drives ATP production via ATP synthase rotation.

  • Photosystem I Role: Functions similarly to PSII and contributes to electron transport.

  • Chlorophyll Activity: Ejects electrons to the second electron transport chain in the thylakoid membrane.

  • Electron Replacement: Electrons in PSI are replenished from PSII's electron transport chain.

  • NADPH Formation: Electrons from PSI reduce NADP+ to form NADPH.

  • Pathway Differences: Inquiry into differences between noncyclic and cyclic pathways.

  • Noncyclic Pathway Overview:

    • Begins with energy transfer to PSII.

    • Ejected electrons enter the electron transport chain.

  • Noncyclic Pathway Mechanism: It's the standard light-dependent reaction pathway.

  • Cyclic Pathway: Cycles electrons back to PS I.

  • Cyclic Pathway Function: Uses electron energy to pump H+ into the thylakoid compartment.

  • Byproducts of Cyclic Pathway: No NADPH or O2 formation, relies solely on PSI.

  • Cyclic Pathway Function: Does not involve photolysis; hence no oxygen production.

  • Cyclic Pathway Contribution: Aids in photoprotection.

  • Summary of Inputs/Outputs:

    • Inputs: 12 H2O, 12 NADP+, 18 ADP + 18 Pi, light energy.

    • Outputs: 6 O2, 12 NADPH, 18 ATP.

  • Thylakoid Changes Inquiry: Changes in thylakoid space as electrons move in the transport chain.