Question:

Protons or hydrogen ions produced by photolysis of water accumulate in the lumen of thylakoids. Photolysis of water takes place in inner membrane of thylakoid.

Updated On: Oct 14, 2024

If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false

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The Correct Option is B

Solution and Explanation

The first step in photosynthesis is the light-driven oxidation (splitting or photolysis) of water. It provides the electrons for the photosynthetic electron transport chains as well as protons for the establishment of a proton gradient. It occurs on the lumenal side of the thylakoid membrane. During photolysis, water is oxidised to oxygen, protons and electrons. Protons accumulate in the lumen.

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Concepts Used:

Calvin Cycle

The Calvin cycle is a process that plants and algae use to turn carbon dioxide from the air into sugar, the food autotrophs need to grow.

Every living thing on Earth depends on the Calvin cycle. Plants depend on the Calvin cycle for energy and food. Other organisms, including herbivores, also depend on it indirectly because they depend on plants for food. Even organisms that eat other organisms, such as carnivores, depend on the Calvin cycle. Without it, they wouldn't have the food, energy, and nutrients they need to survive.

Stages of C3 Cycle:

It is divided into three main stages:

Carbon fixation

In this stage the carbon dioxide combines with RuBP, to be reduced and attached to an organic molecule. It forms 2 molecules of 3-PGA (3-phosphoglyceric acid). The enzyme which is used in this process to catalyse the reaction is ribulose bisphosphate carboxylase/oxygenase. The enzyme works rather slowly and processes only 3 molecules of RuBP per second. The process is called carbon fixation because carbon dioxide is fixed from an inorganic form to organic molecules.

Reduction

In this step, 3-PGA (3-phosphoglyceric acid) is converted into simple sugar- G3P (Glyceraldehyde-3 phosphate). ATP and NADPH is utilized in this stage as energy sources and the energy is transferred to sugar molecules for long storage purposes.

Regeneration

It is the third stage of the Calvin cycle and is a complex process that requires ATP. In this stage, some of the G3P molecules are used to produce glucose, while others are recycled to regenerate the RuBP acceptor.