Photosynthesis

• Overall equation: 6H2O + 6CO2 + Solar Energy ➡️ C6H12O6 + 6O2
• Photosynthesis

  1. Light dependent reactions

  2. Light independent reactions
• Photosynthesis occurs in 2 stages
• Light dependent reactions are also known as Light Reactions
• Light independent reactions are also known as Calvin Cycle or Dark Reactions
• Chloroplast


  • Thylakoids arranged in piles, known as grana
  • Thylakoid membrane contains pigment called chlorophyll
• Stroma


  Fluid-filled space around the grana
• Lumen


  Space inside the thylakoid discs
• Photons


  Carry energy
• Visible wavelengths of light associated with photons of distinct amount of energy
• Absorption of photons

  Determined by energy levels of electrons in the molecule doing the absorbing
• An atom or molecule can absorb photons only if they have an amount of energy that is exactly equal to the difference between two energy levels
• Pigments

  • Absorb certain wavelengths of light
  • Photosynthetic pigments trap light energy and pass it on to other compounds
• Light-dependent reactions (LDR)

  1. Pigments embedded in the thylakoid membranes absorb light energy, initiating the LDR first step

  2. Eventually, the energy is used to synthesize high-energy compounds
• Chlorophyll a and chlorophyll b are green, carotenoids are yellows and oranges, anthocyanins are red, blue, and purple
• Photosynthesis occurs in the chloroplast