Chapter5.Photosynthesisppt

Chapter 5: Photosynthesis

Overview of Photosynthesis

• Photosynthesis: Conversion of light energy into chemical energy.

• Importance: It's the fundamental process by which plants synthesize food, using sunlight.

Requirements for Photosynthesis

• Essential Inorganic Molecules:

  • Carbon Dioxide (CO2): Uptake through leaf openings (stomata).

  • Water (H2O): Absorbed by roots from soil.

• Location: Primarily in plants, with some bacteria and protists also being photosynthetic autotrophs.

  • Photosynthetic Autotrophs: Convert solar energy to generate organic molecules.

The Photosynthesis Process

• Chloroplasts:

  • Organelle where photosynthesis occurs.

  • Located in the mesophyll tissue of leaves and filled with a viscous liquid called stroma.

  • Contains thylakoids: Membranous structures where light reactions take place.

• By-Product: Oxygen gas is released during photosynthesis.

Photosynthesis Equation

• Overall Equation:

  • Sugars are synthesized from CO2 and H2O, oxygen is released.

  • Represents a reversal of cellular respiration processes.

Major Parts of Photosynthesis

1. Light Reactions:

   • Convert solar energy into chemical energy (ATP and NADPH).

   • Occur in the thylakoid membranes.

2. Calvin Cycle:

   • Converts CO2 into sugar using the chemical energy generated from light reactions.

   • Energized electrons from light are used in sugar production.

The Nature of Light

• Photons: High-speed particles constituting light.

• Electromagnetic Spectrum: Range of all types of radiation; visible light is a critical portion for photosynthesis.

• Chlorophyll Pigments:

  • Absorb specific wavelengths of light, converting it into chemical energy.

Capturing Light Energy

• Photosystems: Molecular devices capturing light energy from photons.

  • Chlorophyll's electrons gain energy upon photon absorption.

  • Energy is then passed on to the Calvin Cycle for sugar production.

Light Reactions

• Involves two types of photosystems:

  • Photosystem II: Initiates the reaction, splitting water to release electrons.

  • Photosystem I: Produces NADPH from NADP+ and light energy.

• Electron Transport Chains:

  • Two chains facilitate the movement of electrons, aiding in ATP synthesis and reducing NADP+ to NADPH.

The Calvin Cycle

• Process: Converts CO2 into glucose.

  • Steps Involved:

    1. Carbon Fixation: CO2 is added to RuBP, creating unstable intermediates.

    2. Reduction Phase: Intermediates split to form G3P.

    3. Release: One molecule of G3P exits to form glucose.

    4. Regeneration: RuBP is recycled to continue the cycle.

• Output: Requires 6 turns of the cycle to produce one glucose molecule.

Summary

• Photosynthesis is integral for life on Earth, providing both food for plants and oxygen as a by-product. Understanding its mechanism sheds light on fundamental biological and ecological principles.