Question

In light reaction of photosynthesis, the chlorophyll is subjected to (a) Destruction (b) Permanent reduction (c) Oxidation and reduction (d) Neutralization

Short answer

The correct answer is (c) Oxidation and reduction.

Step-by-step solution

Understand photosynthesis

Photosynthesis is a chemical process in plants, which converts light energy to chemical energy. The chemical energy is stored in the bonds of glucose, a type of sugar. The process can be divided into two phases: the light-dependent reactions (also known as the light reaction) and the light-independent reactions (also known as the Calvin cycle or dark reaction).

Discuss the light reaction

The light reaction of photosynthesis takes place in the thylakoid membrane of the chloroplasts. Here, chlorophyll (a type of pigment) absorbs light energy and uses it to initiate a series of biochemical reactions. This process involves two crucial steps: (i) oxidation of water molecules and (ii) reduction of the electron carrier molecules (NADP+ to NADPH). Therefore, chlorophyll is subjected to both oxidation and reduction during the light reactions of photosynthesis.

Identify the right answer

The options provided in the question are (a) Destruction, (b) Permanent reduction, (c) Oxidation and reduction, and (d) Neutralization. Given the information provided in step 2, it's clear that stating chlorophyll is subjected to 'Oxidation and reduction' during the light reactions of photosynthesis is the correct answer.

Key concepts

Chlorophyll Oxidation and Reduction

Grasping the concept of chlorophyll's role during the light reactions of photosynthesis is akin to unraveling the magic plants perform with sunlight. Chlorophyll molecules in plant cells are vital for absorbing the energy from light. This energy is then harnessed to split water molecules in a process known as photolysis.

During this stage, chlorophyll acts as a catalyst and undergoes a series of oxidation and reduction reactions. Oxidation involves the loss of electrons, which occurs when water molecules split and oxygen is released as a byproduct. Reduction, on the other hand, happens when the energized electrons from the chlorophyll are transferred to a carrier molecule, typically NADP+, converting it into NADPH.

Understanding that chlorophyll is not destroyed but rather cyclically oxidized and reduced helps clarify how energy from light is transformed into a chemical form. This cyclical nature of chlorophyll's reactions is essential because it allows the molecule to continue absorbing light and participating in the process again, which is crucial for the ongoing production of glucose.

Photosynthesis Stages

Photosynthesis is a cornerstone biological process that allows plants to produce food from sunlight. It unfolds in two main stages: the light reactions and the Calvin cycle. The light reactions harness energy from sunlight and create energy-carrying molecules, while the Calvin cycle uses those molecules to produce glucose.

Light Reactions

In the light reactions, chloroplasts capture sunlight to produce ATP and NADPH. Water is split to provide electrons and protons, and it releases oxygen as a waste product. This stage sets the stage for the energy needs of the second phase.

Calvin Cycle

Following the light reactions, the Calvin cycle (or dark reactions) utilizes the ATP and NADPH from the light phase to convert carbon dioxide into glucose. This occurs in the stroma of the chloroplast and doesn't require light, hence it can proceed both day and night as long as the energy carriers from the light reactions are available.

Photosynthetic Pigments

Photosynthetic pigments are the molecules that absorb light energy and initiate photosynthesis. The primary pigment is chlorophyll, which comes in two main forms, chlorophyll a and chlorophyll b. While both are green, they absorb light of slightly different wavelengths, which broadens the spectrum of light that a plant can use.

Aside from chlorophyll, there are accessory pigments like carotenoids and phycobilins. Carotenoids, such as beta-carotene, give plants their yellow, orange, or red hue and absorb light that chlorophyll cannot, effectively widening the range of light that can be utilized for photosynthesis. Phycobilins, found in algae, absorb light in the blue spectrum. These pigments work together in a complex antenna system, ensuring that as much light as possible can be converted into chemical energy.