Photosynthesis

• Equation

  6 CO2 + H2O + Energy (sunlight) --> C6H12O6 + 6 CO2
• Autotrophs: Organisms that can produce their own energy
• Photoautotrophs: produce their own energy by using light energy
• Chloroplast

  • grana (made of flat structures called thykaloid membranes)

  • Thykaloids contain chlorophyll
  • Stroma in chloroplast, contain enzymes for photosynthesis
• Chlorophyll: a green pigment, which is responsible for the absorption of light to provide energy for photosynthesis.
• Sunlight: visible light that is made up of a spectrum of colours with wave length from a violet at 400 nm to red at 700nm
• Oxidation: The loss of electrons
• Reduction: The gain of electrons
• Electron transport chain: A series of oxidation/reduction reactions that occur in the inner mitochondrial membrane where electrons are passed down from a higher energy state to slowly release its energy
• Phosphorylation: A reaction in which a phosphate group is added to a molecule.


  ADP + P --> ATP
• Photosystem II (p680, non-cyclic): two electrons become excited and move to a higher energy level, electrons are then passed through the ETC and as an enzyme is reduced energy produced, energy is left over to go to p700
• Photolysis: splitting water
• Photosystem 1 (p700): chlorophyll traps suns energy, electron becomes excited and moves to a higher energy level, said electron is not stable and is passed through the ETC to return to its stable state. Energy is released to produce ATP
• NADP+ is the final electron acceptor --> NADPH

  If NADP+ does not accept electrons, they cycle back to p700
• Light dependant reaction:

  1. Light energy is trapped by chlorophyll
  2. Light energy is used to split water molecules to replace used electrons
  3. Electrons freed up enter photosystem II then photosystem I
  4. Through each photosystem, electrons are passed down to the ETC, NADP+ is the final acceptor of ETC in photosystem I
  5. ATP is produced through phosphorylation
• Chemiostasis: using energy from hydrogen to bind ADP + P --> ATP
• Dark Reaction: Dependant on light reaction to provide ATP, hydrogen and electrons
• Dark Reaction (Carbon reduction reaction):

  1. CO2 (1 carbon) combines with RuBP (5 carbon) --> 6 carbon molecule
  2. The unstable 6 carbon molecule immediately splits into two 3 carbon molecules called PGA
  3. 2 PGAL molecules can combine to form glucose
• Limiting Factors

  Temperature: all enzymes work slowly and below 5 degrees celcius there is little to no PS. Temps greater than 30 enzyme activity is decreased
• Limiting Factors:

  Light intensity: low light yeilds decreased photolysis, which decreases O2 and ATP production
• Limiting Factors:

  CO2 concentration: Below 0.01% Rubisco (enzyme that fixes carbon) is ineffective. Between 0.01% and 0.04% PS is slow.