Summary
In the thylakoid membranes, light splits water, releasing oxygen and making ATP and NADPH.
In depth
Photosystem II splits water (photolysis), releasing electrons, protons and oxygen. Electrons pass along a chain to PSI, pumping protons, which drive ATP synthase (photophosphorylation). At PSI, NADP+ is reduced to NADPH.
Non-cyclic flow produces both NADPH and ATP. Two photosystems work in series. Proton gradient depends on water splitting inside the lumen and the Q cycle.
Common mistake: the oxygen released comes from water, not from carbon dioxide.
Frequently asked questions
What is Light-Dependent Reactions?
In the thylakoid membranes, light splits water, releasing oxygen and making ATP and NADPH.
Which area of biology covers Light-Dependent Reactions, and how advanced is it?
Light-Dependent Reactions is one of the 56 topics in Plant Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Z-Scheme of Electron Transport, Photosynthesis, Cyclic Photophosphorylation.
Can you give an example of Light-Dependent Reactions?
DCMU herbicide blocks electron transport in PSII.
What should I learn before Light-Dependent Reactions?
Work through the Beginner topics in Plant Biology first, such as Plant Kingdom, Photosynthesis, Chlorophyll, then return to Light-Dependent Reactions. Intermediate topics assume the Beginner vocabulary.
What topics are related to Light-Dependent Reactions?
The closest topics to Light-Dependent Reactions are Z-Scheme of Electron Transport, Photosynthesis, Cyclic Photophosphorylation, Calvin Cycle. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Light-Dependent Reactions?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Light-Dependent Reactions. To practise the whole of Plant Biology, use the Plant Biology quiz.
How is Light-Dependent Reactions different from Z-Scheme of Electron Transport?
Light-Dependent Reactions: In the thylakoid membranes, light splits water, releasing oxygen and making ATP and NADPH. Z-Scheme of Electron Transport: Electrons flow from photosystem II to photosystem I through carriers, pumping protons for ATP synthesis. Read both side by side and note what each one explains.
What is a common mistake about Light-Dependent Reactions?
The oxygen released comes from water, not from carbon dioxide.
How should I study Light-Dependent Reactions step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Z-Scheme of Electron Transport and explain the difference aloud. Finally, take the Plant Biology quiz and come back to this page for any question you miss.