Photosynthesis Notes PDF

Comprehensive Notes on Photosynthesis Definition: Photosynthesis is the biological process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. It primarily occurs in the chloroplasts of plant cells. Equation: Word Equation: Carbon dioxid...

Comprehensive Notes on Photosynthesis Definition: Photosynthesis is the biological process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. It primarily occurs in the chloroplasts of plant cells. Equation: Word Equation: Carbon dioxide + Water -> Glucose + Oxygen (In the presence of sunlight and chlorophyll) Chemical Equation: 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2 Key Concepts: 1. Autotrophs: Organisms that produce their own food (e.g., plants, algae) using photosynthesis. 2. Energy Conversion: Light energy -> Chemical energy stored in glucose. 3. Pigments: Chlorophyll absorbs light (red and blue wavelengths) and reflects green light. Accessory pigments include carotenoids and xanthophylls. 4. Organelles: Photosynthesis occurs in chloroplasts, specifically in: - Thylakoid membranes: Site of light-dependent reactions. - Stroma: Site of light-independent reactions (Calvin Cycle). Stages of Photosynthesis: 1. Light-Dependent Reactions (Photo Phase): - Occur in the thylakoid membranes. - Inputs: Light energy, water (H2O), ADP, and NADP+. - Outputs: Oxygen (O2), ATP, and NADPH.  - Key Processes: Photon absorption, photolysis (splitting of water), and electron transport chain (ETC). 2. Light-Independent Reactions (Calvin Cycle / Dark Phase): - Occur in the stroma of chloroplasts. - Inputs: Carbon dioxide (CO2), ATP, NADPH. - Outputs: Glucose (C6H12O6), ADP, NADP+. - Key Steps: 1. Carbon Fixation: CO2 combines with RuBP, catalyzed by Rubisco. 2. Reduction Phase: ATP and NADPH reduce intermediates to form G3P. 3. Regeneration: RuBP is regenerated. Factors Affecting Photosynthesis: 1. Light Intensity: Higher intensity increases rate until saturation point. 2. Carbon Dioxide Concentration: Higher CO2 levels boost rate until limiting factors intervene. 3. Temperature: Optimal temperatures (25-30 degrees Celsius); extreme highs/lows hinder enzyme activity. 4. Water Availability: Lack of water slows photosynthesis; stomata closure reduces CO2 uptake. 5. Chlorophyll Levels: Healthy chlorophyll is crucial for absorbing light. Significance of Photosynthesis: 1. Produces O2, supporting life on Earth. 2. Forms the base of food chains by producing glucose. 3. Removes CO2 from the atmosphere, balancing the carbon cycle. 4. Reduces the greenhouse effect. Comparison: Photosynthesis vs. Cellular Respiration | Feature | Photosynthesis | Cellular Respiration | |-----------------------|------------------------------------------|---------------------------------------| | Purpose | Energy storage (glucose production) | Energy release (ATP production) | | Location | Chloroplasts | Mitochondria | | Energy Source | Light energy | Chemical energy (glucose) | | Reactants | CO2, H2O, light | C6H12O6, O2 | | Products | C6H12O6, O2 | CO2, H2O, ATP | Real-Life Applications: 1. Agriculture: Optimizing light, water, and CO2 can maximize crop yield. 2. Global Carbon Balance: Forests act as carbon sinks due to photosynthesis. 3. Biofuels: Plants (e.g., algae) use photosynthesis to produce biomass for renewable energy. 4. Artificial Photosynthesis: Research aims to replicate photosynthesis to create sustainable energy sources.