What is Photosynthesis?
The word Photosynthesis is derived from the Greek words. This means combining together with the help of light.
- Photosynthesis is the process by which green plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose (a type of sugar) and oxygen. It is a vital process that sustains life on Earth by producing oxygen and serving as the primary source of energy for most ecosystems.
- All green plants and a few other autotrophic organisms utilize photosynthesis to synthesize nutrients by using carbon dioxide, water and sunlight. The by-product of the photosynthesis process is oxygen.
Photosynthesis Equation
Photosynthesis reaction involves two reactants, carbon dioxide and water. These two reactants yield two products, namely, oxygen and glucose. Hence, the photosynthesis reaction is considered to be an endothermic reaction. Following is the photosynthesis formula:6CO2 + 6H2O -> C6H12O6 + 6O2
Chlorophyll
Chlorophyll is a green pigment found in the chloroplasts of the plant cell and in the mesosomes of cyanobacteria. This green colour pigment plays a vital role in the process of photosynthesis by permitting plants to absorb energy from sunlight. Chlorophyll is a mixture of chlorophyll-a and chlorophyll-b. Besides green plants, other organisms that perform photosynthesis contain various other forms of chlorophyll such as chlorophyll-c1, chlorophyll-c2, chlorophyll-d and chlorophyll-f.
Process of Photosynthesis
The photosynthesis process takes place in cell organelles called chloroplasts.
- These organelles contain a green-colored pigment called chlorophyll, which is responsible for the characteristic green coloration of the leaves.
- As already stated, photosynthesis occurs in the leaves and the specialized cell organelles responsible for this process are called chloroplasts.
- A leaf comprises a petiole, epidermis, and a lamina. The lamina is used for absorption of sunlight and carbon dioxide during photosynthesis.
Steps involved in Photosynthesis:
- During the process of photosynthesis, carbon dioxide enters through the stomata, water is absorbed by the root hairs from the soil and is carried to the leaves through the xylem vessels. Chlorophyll absorbs the light energy from the sun to split water molecules into hydrogen and oxygen.
- The hydrogen from water molecules and carbon dioxide absorbed from the air are used in the production of glucose. Furthermore, oxygen is liberated out into the atmosphere through the leaves as a waste product.
- Glucose is a source of food for plants that provide energy for growth and development, while the rest is stored in the roots, leaves, and fruits, for their later use.
- Pigments are other fundamental cellular components of photosynthesis. They are the molecules that impart color and they absorb light at some specific wavelength and reflect back the unabsorbed light. All green plants mainly contain chlorophyll a, chlorophyll b, and carotenoids which are present in the thylakoids of chloroplasts. It is primarily used to capture light energy. Chlorophyll-a is the main pigment.
Process of Photosynthesis
The process of photosynthesis can be divided into two main stages:
- Light-dependent reactions: These reactions occur in the thylakoid membranes of chloroplasts and require sunlight. They convert light energy into chemical energy in the form of ATP and NADPH.
- The chemical equation in the light reaction of photosynthesis can be reduced to:2H2O + 2NADP+ + 3ADP + 3Pi -> O2 + 2NADPH + 3ATP
- Light-independent reactions/Dark Reaction (Calvin cycle): These reactions occur in the stroma of chloroplasts and do not directly require sunlight. They use the ATP and NADPH produced in the light-dependent reactions to convert carbon dioxide into glucose.
- The chemical equation for the dark reaction can be reduced to: 3CO2 + 6 NADPH + 5H2O + 9ATP -> G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi
* G3P - glyceraldehyde-3-phosphate
Importance of Photosynthesis
Photosynthesis is crucial for several reasons:
- It produces oxygen, which is essential for the survival of aerobic organisms.
- It serves as the primary source of energy for most ecosystems, as glucose is used by organisms as fuel.
- It plays a significant role in the global carbon cycle by removing carbon dioxide from the atmosphere and converting it into organic compounds.
