c1.3_Photosynthesis

C1.3 Photosynthesis: Key Concepts

• Interaction and Interdependence
  • Photosynthesis is essential for life, converting light energy into chemical energy, producing carbohydrates and oxygen, which are crucial for complex ecosystems.

C1.3.1 - Transformation of Light Energy to Chemical Energy

• Photosynthesis converts light energy into chemical energy.
• Key Reaction:
  $\text{Water} + \text{Carbon Dioxide} \xrightarrow{\text{light}} \text{Glucose} + \text{Oxygen}$

C1.3.2 - Reactions of Photosynthesis

• Light-dependent Reactions
  • Occur in thylakoids
  • Use light energy to split water (photolysis), producing oxygen as a by-product.
• Light-independent Reactions (Calvin Cycle)
  • Occur in the stroma
  • Utilize ATP and NADPH to synthesize glucose from carbon dioxide.

C1.3.3 - Oxygen Production

• Oxygen as a by-product comes from the splitting of water during photolysis in plants, algae, and cyanobacteria.

C1.3.5 - Light Absorption by Pigments

• Photosynthetic pigments (e.g., chlorophyll) absorb specific wavelengths of light.
  • Higher energy = shorter wavelength
  • Excited electrons aid in the conversion to chemical energy.

C1.3.4 - Chromatography of Pigments

• Chromatography is used to analyze and identify different photosynthetic pigments by their Rf values.
  • $Rf = \frac{\text{Distance travelled by pigment}}{\text{Distance travelled by solvent}}$

C1.3.6 - Absorption and Action Spectra

• Absorption Spectrum: Wavelengths absorbed by chlorophyll vs. Action Spectrum: Rates of photosynthesis at different wavelengths.

C1.3.7 - Investigating Limiting Factors

• Variables affecting photosynthesis include:
  • Carbon Dioxide: Varying concentration affects the rate.
  • Light Intensity: Increasing intensity increases rates until saturation.
  • Temperature: Higher temperatures increase rates to a point before enzyme denaturation.

C1.3.8 - CO2 Enrichment Experiments

• FACE Experiments: Assess natural ecosystem responses to increased CO2 concentrations.
  • Examines crop yield and plant responses.

C1.3.9 - Photosystems Overview

• Photosystems are pigment arrays in membranes that emit excited electrons.
  • Photosystem I and II: Each has different functions and roles in photophosphorylation processes.

C1.3.10 - Advantages of Pigment Diversity

• Multiple pigments capture a broader range of solar energy and protect against damage.

C1.3.11 - Photolysis in Photosystem II

• Importance of photolysis: Produces oxygen and protons that contribute to the proton gradient.

C1.3.12 - ATP Production

• ATP is formed through chemiosmosis utilizing a proton gradient established via electron transport chains.

C1.3.13 - NADP Reduction

• NADP is reduced to NADPH in the presence of hydrogen ions and electrons from Photosystem I.

C1.3.14 - Thylakoids’ Role

• Thylakoids are the site of light-dependent reactions, where ATP and NADPH are produced.

C1.3.15 - Carbon Fixation by Rubisco

• Rubisco catalyzes the reaction of CO2 with RuBP, producing glycerate-3-phosphate (GP).

C1.3.16 - Synthesis of Triose Phosphate

• GP is converted into triose phosphate (TP) using ATP and NADPH.

C1.3.17 - Regeneration of RuBP

• Five TP molecules regenerate three RuBP, facilitating continual Calvin cycles.

C1.3.18 - Synthesis of Other Compounds

• Other biomolecules (e.g., amino acids and lipids) derived from intermediates in the Calvin Cycle.

C1.3.19 - Interconnectedness of Reactions

• Light-dependent and light-independent reactions depend on each other for functionality.

Review Questions

• Identify reactants and products of photosynthesis.
• Explain significance of photosynthesis for life on Earth.
• Discuss implications of FACE experiments on climate change predictions.

Additional Notes

• Variables in Experiments: Identify independent (manipulated) and dependent variables (measured) during experiments.
• Hypotheses: Must be tested and are subject to revisions based on experimental evidence.