4. The process of photosynthesis which leads to formation of glucose from C0₂ and H₂0 is an example of
(1) Oxidation         (2) Reduction
(3) Condensation   (4) Fixation

 Photosynthesis is a fundamental biological process by which green plants, algae, and some bacteria convert light energy into chemical energy, producing glucose from carbon dioxide (CO2) and water (H2O). This process sustains life on Earth by providing organic compounds and oxygen.

Understanding the nature of the chemical changes during photosynthesis is essential, especially whether it involves oxidation, reduction, condensation, or fixation.

Photosynthesis Overview

The overall simplified reaction for photosynthesis is:

6CO2+6H2O+light energy→C6H12O6+6O26CO2+6H2O+light energy→C6H12O6+6O2

Here, carbon dioxide and water are the reactants, and glucose and oxygen are the products.

Oxidation and Reduction in Photosynthesis

Photosynthesis is a redox (oxidation-reduction) process involving simultaneous oxidation and reduction:

• Oxidation: Water molecules (H2O) are oxidized, losing electrons and protons to form oxygen gas (O2). This releases electrons needed for the reduction reactions.

• Reduction: Carbon dioxide (CO2) molecules gain electrons and hydrogen ions to form glucose (C6H12O6). This gain of electrons is a reduction process.

Thus, the formation of glucose from CO2 is fundamentally a reduction process because carbon atoms in CO2 gain electrons and hydrogen to form the carbohydrate.

Why Photosynthesis Is Considered a Reduction Process for Glucose Formation

• Carbon dioxide molecules have carbon in a highly oxidized state.

• During photosynthesis, carbon atoms in CO2 are converted into a more reduced form in glucose.

• This involves the addition of electrons and hydrogen atoms to carbon, which defines reduction.

• The energy for this reduction comes from sunlight absorbed by chlorophyll pigments.

Other Terms: Condensation and Fixation

• Condensation: A chemical process where two molecules combine with the loss of a small molecule (often water). While condensation reactions occur in biosynthesis, the overall photosynthesis process is not primarily classified as condensation.

• Fixation: Refers specifically to the incorporation of inorganic carbon (CO2) into an organic molecule. Carbon fixation is a stage within photosynthesis (Calvin cycle), but the overall process leading to glucose formation is best described as a reduction of CO2.

Summary of Options

Final Answer

The process of photosynthesis that leads to the formation of glucose from CO2 and H2O is an example of:

(2) Reduction

Additional Insights

Photosynthesis involves two key stages:

• Light-dependent reactions: Water is oxidized to oxygen, releasing electrons and protons.

• Light-independent reactions (Calvin cycle): CO2 is fixed and reduced to form glucose using ATP and NADPH produced in the light reactions.

This dual nature of photosynthesis as a redox process is critical for energy flow in ecosystems and the global carbon cycle.