Plants, algae and some microbes use sunlight to create glucose in a process which we called as photosynthesis. The complex process is the backbone of life on earth, supporting the food chain and providing oxygen for the atmosphere.
The Role of Chlorophyll in Photosynthesis)
Chlorophyll is essential to photosynthesis. It absorbs light energy from the sun and transfer it to other molecules, which are then used to convert carbon dioxide and water into glucose and oxygen.
The Process of Photosynthesis
Photosynthesis occurs in specialized organelles called chloroplasts, which contain pigments such as chlorophyll. The process can be divided into two stages: The Light Dependent Reaction and The Light Independent Reaction.
Light- Dependent Reactions
In light-dependent reactions, light energy is absorbed by the pigment in thylakoid membrane. ATP and NADPH, which are necessary for the light-independent processes, are subsequently produced using this energy.
Steps of Light- Dependent Reaction
- Light Absorption
Pigments including chlorophyll absorb light.
- Excitation of Electrons
Electrons are excited by the energy of the absorbed light and are then transferred to a unique molecule known as an electron acceptor.
- Transfer of Electrons
The electrons are transferred by electron carriers, to produce ATP and NADPH.
- ATP Synthesis
Chemiosmosis is the method by which ATP is created via the proton gradient.
- Reduction of NADP+
Electrons ultimately reduce NADP+ to form NADPH.
Light- Independent Reactions (Calvin Cycle)
The calvin cycle take place in the stroma of chloroplasts and involves the fixation of carbon dioxide into glucose using the ATP and NADPH produced in the light- dependent reactions.
Steps of Light- Independent Reaction
- Carbon Fixation
CO2 is fixed into a 3-carbon molecule via enzyme activity.
- Reduction
The 3-PGA molecules are reduced to form glyceraldehyde- 3- phosphate ( G3P) using the ATP and NADPH produced in the light- dependent reactions.
- Regeneration
The G3P molecules are used to regenerate the RuBP molecule, which is essential for cycle to continue.
- Production of Glucose
Through a sequence of events, glucose is produced using the G3P molecules.
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Importance of Photosynthesis
- Primary Production
Photosynthesis is the primary source of energy for most ecosystems, supporting the food chain and providing food chain for growth and development.
- Oxygen Production
The majority of living things depend on the oxygen produced during photosynthesis to survive.
- Climate Regulation
Photosynthesis helps regulate Earth’s climate by removing CO2 from the atmosphere and releasing oxygen.
- Food Source
Glucose produced during photosynthesis supports the food chain, from herbivores to carnivores.
Factors Affecting Photosynthesis
Photosynthesis is influenced by various factors, which can be broadly categorized into environmental, plant related and other factors.
Environmental Factors
- Light Intensity
Increased light intensity can enhance photosynthesis, but excessive light can cause photo inhibition.
- Temperature
Optimal temperature ranges support photosynthesis, while extreme temperatures can inhibit the process.
- Water Availability
Adequate water supply is crucial for photosynthesis, as water is a reactant in the process.
Plant- Related Factors
- Leaf Structure
Leaf thickness, surface area and venation can affect photosynthesis.
- Chlorophyll Content
Chlorophyll is essential for photosynthesis, and its content can vary among plant species and environment.
- Nutrient Availability
Adequate nutrients supply such as nitrogen, phosphorus and potassium is necessary for photosynthesis.
Other Factors
- Salinity
High salts levels can reduce photosynthesis by altering plant water relations and nutrient uptake.
- Drought
Water stress can reduce photosynthesis by limiting water availability and altering plant physiology.
- Herbicides and Pesticides
Certain chemicals can damage plant tissues and reduce photosynthesis.
Types of Photosynthesis
Plants have three ways to make food: C3, C4 and CAM. Each way helps plants survive in different environments.
C3 Photosynthesis
- Most Common Type
The majority of plant species engage in C3 photosynthesis, which is the most prevalent kind.
- Calvin Cycle
C3 plants use the Calvin cycle to fix CO2 into a 3- carbon molecule (3- phosphoglycerate).
- CO2 Fixation
CO2 is fixed directly into the Calvin cycle.
Examples
Rice, Soybeans, Wheat, Shrubs.
C4 Photosynthesis
- Adaptation to Hot and Dry Environment
C4 plants have adapted to live in arid, hot climates.
- CO2 Concentration
C4 plants concentrate CO2 in the leaves. Reducing photorespiration and increasing photosynthetic efficiency.
- 4-carbon Molecule
4-carbon molecule (malate or oxaloacetate) is fixed with CO2.
Example
Plants like corn, sugarcane and sorghum.
CAM Photosynthesis
- Adaptation to Arid Environments
CAM plants have evolved to conserved water in arid environment.
- Night time CO2 Uptake
CAM plants take up CO2 at night, storing it in the form organic acids.
Example
Plant like cacti, succulents and some epiphytes.
Comparison of C3, C4 and CAM Photosynthesis
- Water-Efficiency
The most water-efficient plants are CAM and C4 varieties.
- C02 Fixation
C3 plants fix CO2 directly into the Calvin Cycle, while C4 and CAM plants use additional mechanisms to concentrate CO2.
- Photosynthetic Efficiency
Particularly under hot and dry conditions, C4 plants are more efficient at photosynthetic processes than C3 plants.
Applications of Photosynthesis
- Agriculture
Understanding photosynthesis can help to improve crop yields and plant growth.
- Ecology
Studying photosynthesis can provide insights into ecosystem dynamics and the impact of environmental changes.
- Biotechnology
Photosynthesis research has led to the development of the new technologies, such as biofuels and genetically modified crops.
- Biofuels
Photosynthesis is used to produce biofuels, a renewable energy source.
- Space Exploration
Photosynthesis is being researched for potential use in space exploration and life support system.
- Climate Change Mitigation
Photosynthesis helps regulate CO2 levels, mitigating climate change.
These application highlight the importance of photosynthesis in the various field.
