Chapter_4_Biology12

Chapter 4: Photosynthesis

Specific Expectations

  • Terminology Related to Metabolism

    • C2.1: Use appropriate terminology related to metabolism (Photosynthesis steps).

  • Laboratory Investigation

    • C2.3: Conduct a laboratory investigation into photosynthesis to identify products and display them appropriately.

  • Chemical Changes and Energy Conversions

    • C3.2: Explain chemical changes and energy conversions during photosynthesis.

  • Matter and Energy Transformations

    • C3.4: Describe and illustrate matter and energy transformations, including roles of oxygen and chloroplasts.

Overview of Photosynthesis

  • Photosynthesis is crucial for the sustainable management of Canada's boreal forest, impacting both ecology and economy.

  • This process allows trees and plants to convert about 12.5 million tonnes of carbon dioxide into organic compounds annually.

  • Metabolic pathways within cells convert high-energy compounds (like glucose) into usable energy (ATP).

Launch Activity: Seeing Green

  • Chlorophyll absorbs light energy and synthesizes carbohydrates from CO2 and water.

  • Materials Needed:

    • Beaker of chlorophyll solution, light source.

  • Procedure:

    1. Shine a strong light on chlorophyll solution in a dark room.

    2. Observe chlorophyll color at different angles and analyze fluorescence.

Section 4.1: Light-Dependent Reactions

  • Key Terms:

    • Light-dependent reaction, light-independent reaction, thylakoid, pigment, photosystem, photophosphorylation.

  • Photosynthesis transforms sunlight into chemical energy.

  • Only 1-2% of sunlight reaching Earth is used by photosynthesizing organisms (e.g., cyanobacteria, plants).

Energy Conversion

  • Photosynthesis produces 1.4 x 10^15 kg of energy-storing compounds like glucose each year.

  • Structural components (cellulose) and metabolic substances (sugars, amino acids) are made from glucose.

  • General Equation for Photosynthesis:

    • 6CO2 + 6H2O + energy → C6H12O6 + 6O2

Photosystem and Pigments

  • Photosystems: Two types present: PS I (P700) and PS II (P680).

  • Photosystem II absorbs light, creating an energized electron and splitting water, releasing oxygen.

  • Pigments: Chlorophyll a and b absorb red and blue light but reflect green, giving leaves their color.

Structure of Chloroplasts

  • Chloroplasts contain thylakoids, granum, and stroma, essential for photosynthesis.

  • CO2 enters through stomata, while water is absorbed through the roots, entering the thylakoids.

Light Harvesting Complex

  • Pigments, embedded in thylakoid membranes, absorb light energy crucial for energy synthesis.

  • The antenna complex gathers light and transfers energy to the reaction center.

Noncyclic vs. Cyclic Photophosphorylation

  • Noncyclic photophosphorylation: Photon energies from PS II and I create NADPH and ATP for Calvin cycle.

  • Cyclic photophosphorylation: Provides additional ATP without producing NADPH or oxygen.

The Calvin Cycle (4.2)

  • Carbon fixation occurs in the stroma, turning CO2 into G3P, the foundational block for glucose.

  • Enzyme: ribulose bisphosphate carboxylase (RuBisCO) catalyzes initial reactions.

  • Phases of Calvin Cycle:

    1. Carbon dioxide fixation.

    2. Reduction phase - G3P formation.

    3. Regeneration of RuBP.

Adaptations to Photosynthesis

  • C3 Plants: Struggle with photorespiration; can utilize CO2 efficiently under optimal conditions.

  • C4 Plants: Separate initial CO2 fixation and the Calvin cycle reactions to enhance efficiency in hot climates.

  • CAM Plants: Fix CO2 at night, store it for daytime use, minimizing water loss.

Conclusion and Impacts

  • Understanding photosynthesis has implications for agriculture, bioengineering, and combating climate change.

  • Current research focuses on improving efficiency and mimicking photosynthetic processes for sustainable energy solutions.

robot