Photosynthesis

Introduction

Photosynthesis (In Greek: Photo = light; synthesis = combination) is a biochemical process by which green plants produce their food with water and carbon dioxide in presence of sunlight.

Chloroplast

Chloroplasts are cell organelles, found in green plant cells. Chloroplasts contain a green coloured pigment, which is known as chlorophyll.

Structure of Chloroplast

Chloroplasts are membrane bound structures, which are composed of

• Matrix or Stroma
• Grana.

Matrix or stroma is the watery substance that fills the inner part of the chloroplast. Grana (singular-granum) are granular structures which contain the chlorophyll. Grana are embedded in the matrix. Each granum is composed of 5 to 50 sac like structures, called thylakoids. Chlorophyll occurs on these thylakoids.

Chlorophyll

Chlorophyll can absorb sunlight that provides the energy required for the process of photosynthesis.

Photosynthesis- The Process:

Plants absorb water through roots from soil and Atmospheric carbondioxide enters into the leaves through small pores, called stomata. These are the ingredients for sugar production. Chlorophyll absorbs light energy and photosynthesis starts.

Photosynthesis completes in two stages-Light Reaction (or light dependent reaction) and Dark Reaction (or light independent reaction). The overall reaction is as follows:

6H₂O + 6CO₂ ----------> C₂H₂O₂+ 6O₂

Light Reaction

Chlorophyll absorbs sunlight and a series of biochemical reactions take place to produce two compounds, ATP ( Adenosine triphosphate) and NADPH (nicotine adenine dinucleotide phosphate). Water molecule breaks and releases oxygen during the process.

Dark Reaction

t is also called Calvin Cycle. In this stage, atomospheric carbon dioxide is converted to sugar using ATP and NADPH formed in Light Reaction.

Role of Photosynthesis in environmental CO₂balance

Photosynthesis in green plants maintains the CO₂ balance in environment. It removes the CO₂ produced by animals from atmosphere and releases oxygen. Thus gaseous balance in atmosphere is maintained.