Splitting of water in photosynthesis is called photolysis of water or lysis of water molecules which occur by the action of light . In this the water molecules breaks and form hydrogen and oxygen .
H2O-----> 2H+ +2e- + 1/2O2

Question

Splitting of water in photosynthesis is called :a)Dark reactionb)Photolysisc)Electron transferd)PhototropismCorrect answer is option 'B'. Can you explain this answer?

Answer

Answer

Photolysis->splitting of water takes place in lumen of thylakoid involving Ps-2.also known as OEC(oxygen evolving complex).

Answer

Photosynthesis and the Splitting of Water

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. This process occurs in the chloroplasts of these organisms and consists of two main reactions: the light-dependent reactions and the light-independent reactions.

Light-Dependent Reactions

The light-dependent reactions occur in the thylakoid membranes of the chloroplasts. These reactions require light energy to produce ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which are energy-rich molecules used in the light-independent reactions.

During the light-dependent reactions, water molecules are split, and this process is known as photolysis or the splitting of water. The splitting of water is a critical step in photosynthesis as it provides electrons for the photosynthetic electron transport chain and releases oxygen as a byproduct.

Process of Photolysis

Photolysis occurs in the thylakoid membrane within a structure called the photosystem II (PSII). Here is a step-by-step explanation of the process:

1. Absorption of Light: When light energy is absorbed by the chlorophyll molecules in the thylakoid membrane, it excites the electrons in the chlorophyll.

2. Excitation and Electron Transport: The excited electrons are transferred from chlorophyll to a primary electron acceptor. This starts a chain of electron transfers through a series of electron carriers in the thylakoid membrane, known as the electron transport chain.

3. Water Splitting: As the excited electrons are transferred through the electron transport chain, water molecules are split. Each water molecule donates two electrons, two protons (H+), and releases one molecule of oxygen (O2) as a byproduct.

4. Electron Replacement: The electrons lost from the chlorophyll are replaced by the electrons released from water during the splitting process. This maintains the electron flow through the electron transport chain.

5. Formation of ATP and NADPH: The energy released during the transfer of electrons through the electron transport chain is used to pump protons (H+) across the thylakoid membrane, creating a proton gradient. This gradient drives the synthesis of ATP through a process called chemiosmosis. Additionally, the electrons transferred to the photosystem I (PSI) are used to reduce NADP+ to NADPH, which is an energy carrier molecule.

Conclusion

In summary, the splitting of water in photosynthesis, known as photolysis, occurs during the light-dependent reactions in the thylakoid membranes of chloroplasts. This process provides electrons for the photosynthetic electron transport chain and releases oxygen as a byproduct. It is a crucial step in the production of ATP and NADPH, which are used in the subsequent light-independent reactions to convert carbon dioxide into glucose.

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