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The light-dependent reactions begin in photosystem II. In PSII, energy from sunlight is used to split water, which releases two electrons, two hydrogen atoms, and one oxygen atom. When a chlorophyll a molecule within the reaction center of PSII absorbs a photon, the electron in this molecule attains a higher energy level.
- 8.2: The Light-Dependent Reactions of Photosynthesis
How Light-Dependent Reactions Work. The overall function of...
- 8.2: The Light-Dependent Reactions of Photosynthesis
How Light-Dependent Reactions Work. The overall function of light-dependent reactions is to convert solar energy into chemical energy in the form of NADPH and ATP. This chemical energy supports the light-independent reactions and fuels the assembly of sugar molecules. The light-dependent reactions are depicted in Figure 8.2.7 8.2.
When a person turns on a lamp, electrical energy becomes light energy. Like all other forms of kinetic energy, light can travel, change form, and be harnessed to do work. In the case of photosynthesis, light energy is converted into chemical energy, which photoautotrophs use to build basic carbohydrate molecules (Figure 8.9). However ...
A photon strikes the antenna pigments of photosystem II to initiate photosynthesis. The energy travels to the reaction center that contains chlorophyll a and then to the electron transport chain, which pumps hydrogen ions into the thylakoid interior. This action builds up a high concentration of hydrogen ions.
- In with One Energy and Out with Another
- A Recipe For Energy
- Photosystem I and Photosystem II
- The Electron Transport Chain
- The Calvin Cycle: Building Life from Thin Air
The light-dependent reactions take place in the thylakoid membrane, inside chloroplasts. Since they are light 'dependent' reactions, you can guess that these reactions need light to work. Remember that the purpose of this first part of photosynthesis is to convert sunlight energy into other forms of energy? Plants cannot use light energy directly t...
Plants need water to make NADPH. This water is broken apart to release electrons (negatively charged subatomic particles). When water is broken it also creates oxygen, a gas that we all breathe. The electrons must travel through special proteins stuck in the thylakoid membrane. They go through the first special protein (the photosystem II protein) ...
Wait a second... first electrons go through the second photosystem and second they go through the first? That seems really confusing. Why would they name the photosystems that way? Photosystem I and II don't align with the route electrons take through the transport chain because they weren't discovered in that order. Photosystem I was discovered fi...
While at photosystem II and I, the electrons gather energy from sunlight. How do they do that? Chlorophyll, which is present in the photosystems, soaks up light energy. The energized electrons are then used to make NADPH. The electron transport chain is a series of molecules that accept or donate electrons easily. By moving step-by-step through the...
How does something like air become the wood of a tree? The answer lies in what makes up the air. The air holds different elements like oxygen, carbon, and nitrogen. These elements make up molecules like carbon dioxide (CO2). Carbon dioxide is made out of one carbon atom and two oxygen atoms. Plants take the carbon atom from carbon dioxide and use i...
The light-dependent reactions begin in a grouping of pigment molecules and proteins called a photosystem. Photosystems exist in the membranes of thylakoids. A pigment molecule in the photosystem absorbs one photon, a quantity or “packet” of light energy, at a time. A photon of light energy travels until it reaches a molecule of chlorophyll.
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How do light-dependent reactions begin in photosystem II?
How does a photosystem II reaction work?
Where do light-dependent reactions begin?
What is the function of light-dependent reactions in photosynthesis?
How do two photosystems absorb light energy?
What happens at the reaction center during photosynthesis?
As photons are absorbed by pigment molecules in the antenna complexes of Photosystem II, excited electrons from the reaction center are picked up by the primary electron acceptor of the Photosystem II electron transport chain. During this process, Photosystem II splits molecules of H 2 O into 1/2 O 2, 2H +, and 2 electrons.
