Photosynthesis is the conversion of light energy into chemical energy.
Producers (e.g., plants) are crucial as they form the base of food chains by transforming light energy into chemical energy.
This chemical energy is transferred through trophic levels, with some loss at each step.
Photosynthesis Process
Key Components:
Water (H₂O) and Carbon Dioxide (CO₂) are converted into Glucose (C₆H₁₂O₆) with Oxygen (O₂) as a byproduct.
Photolysis: Splitting of water molecules using light energy to obtain hydrogen needed for glucose production.
Oxygen is released during photolysis as a gas.
Historical Significance
Photosynthetic organisms have significantly altered Earth's atmosphere by increasing oxygen levels.
Pigments and Light Absorption
Pigments: Substances that absorb different wavelengths of light.
Chromatography is used to separate and study pigments.
Pigments are transferred to chromatography paper and separated by a solvent.
Retention Factor (RF): Calculated to identify pigments, based on the travel distance of pigments and solvent.
RF = Distance traveled by the pigment/distance traveled by the solvent.
Colors vs. Pigments:
Colors are perceived wavelengths of light.
Pigments absorb/reflect light; the color seen is the wavelength not absorbed.
Chlorophyll
Main pigment in plants; appears green because it reflects green light.
Absorbs blue and red light efficiently but poorly absorbs green light.
Absorption and Action Spectrum
Absorption Spectrum: Shows wavelengths a pigment can absorb.
Action Spectrum: Indicates the effectiveness of different wavelengths in driving photosynthesis.
Measuring Photosynthesis
Limiting Factors: Carbon dioxide concentration, light intensity, and temperature.
Carbon Dioxide: Higher concentration increases rate until enzymes are saturated.
Light Intensity: More light increases rate until a saturation point.
Temperature: Rate increases with temperature until enzymes denature.
Experimental Methods
Measuring oxygen production or CO₂ consumption to determine photosynthesis rates.
Use of Aquatic Plants:
Counting oxygen bubbles as a measure of photosynthesis.
Leaf Disc Method: Measures time for leaf discs to float, indicating oxygen production.
Investigation Techniques
Carbon Dioxide: Boiling water to remove CO₂ or adding sodium hydrogen carbonate to increase it.
Light Intensity: Adjusting proximity or intensity of light source.
Temperature: Using a controlled water bath.
Use of pH sensors to detect CO₂ removal and infer photosynthesis rate.
Large Scale Experiments
Free Air Carbon Dioxide Enrichment (FACE): Experiments to study increased CO₂ impact on ecosystems.