Photosynthesis: Process, Equation, and Pigments

Photosynthesis Equation

• 6 H₂O + 6 CO₂ + sunlight → C₆H₁₂O₆ + 6 O₂
• Reactants: Water, Carbon Dioxide, Sunlight
• Products: Glucose, Oxygen

Photosynthesis and Respiration Relationship

• Photosynthesis produces sugar and oxygen, necessary for respiration.
• Respiration produces ATP; photosynthesis is needed for respiration to begin.

Chloroplast Structure

• (A labeled diagram is needed here based on the information, but is not provided.)

Light, Energy, and Wavelength

• Light is electromagnetic radiation traveling as waves (photons).
• Wavelength is the distance between waves.
• Shorter wavelengths have higher energy (e.g., violet > blue).

Pigments

• Pigments absorb light of specific wavelengths.
• We perceive reflected wavelengths as colors.
• Visible light (380-750 nm) drives photosynthesis.
• Pigments capture light energy to drive photosynthesis.

Plant Pigments

• Chlorophyll (most common) absorbs violet, red, and orange light, reflecting green light.
• Chlorophyll b and carotenoids (orange) are accessory pigments absorbing other wavelengths.
• Different pigment combinations adapt plants to different environments.

Autumn Dormancy

• Plants shift resources to roots to minimize potential damage in cold weather.

Light-Dependent Reactions

• Location: Thylakoids
• Inputs: Sunlight, water
• Outputs: Oxygen, ATP, NADPH
• Photosystem II captures light energy, exciting electrons transferred through the electron transport chain (ETC).
• Water molecules replace lost electrons, releasing oxygen.
• Photosystem I further energizes electrons through another ETC.
• Electrons help create ATP at ATP synthase in the thylakoid membrane.

Photosystems

• Photosystem II: Where water is split and electrons are released.
• ETC: Series of proteins that transport energized electrons.
• Photosystem I: Electrons from Photosystem II arrive here.
• ATP Synthase: Creates ATP from the energy in the electron gradient.

Chlorophyll and Photons

• Absorbing a photon excites an electron in chlorophyll.
• The excited electron moves through the electron transport chain.

Calvin Cycle (Light-Independent Reactions)

• Location: Stroma
• It fixes carbon dioxide using ATP and NADPH. . The Calvin cycle has different phases. Details on these stages were not provided

Plant Types

• C3 Plants:
  • Most common.
  • Carbon fixation produces a three-carbon molecule.
  • Photorespiration occurs when oxygen binds with rubisco (an enzyme necessary for carbon fixation) instead of carbon dioxide; this reduces efficiency during hot, dry days
• C4 Plants:
  • Form four-carbon molecules in mesophyll cells & pass into bundle-sheath cells before entering the Calvin cycle which minimizes photorespiration by maintaining high CO₂ levels.
• CAM Plants:
  • Open stomata at night to conserve water; store CO₂ in organic acids overnight; release CO₂ into the Calvin cycle during the day.

Factors Affecting Photosynthesis

• Light Intensity: Increases rate to a point, then plateaus or declines.
• CO₂ Concentration: Increases rate to a point, then plateaus; Needs free RuBP to bind with CO2
• Temperature: Increases rate until optimal point is reached; above optimal temperatures enzyme activity decreases.

Explore the process of photosynthesis, its equation, and the crucial role of pigments. Understand the relationship between photosynthesis and respiration, as well as the structure of chloroplasts. Learn about light, energy, wavelengths, and how plant pigments capture light to drive photosynthesis.