Photosynthesis

Autotroph

  • organisms that make their own food


Heterotroph

  • organism that cannot synthesize their own food

  • consume other organisms/organic matter


Chloroplasts: Definition, Structure, Functions, Diagram


Formula for Photosynthesis

6CO2 + 6H2O + light energy —> C6H12O6 + 6O2

carbon dioxide + water + light energy —> glucose + oxygen


Electron Acceptors

  • different energy capturing processes use different types of electron acceptors

    • Photosynthesis — NADP+ and NADPH

    • Cellular Respiration — O2, H2O, NADH, FADH2


Light Reaction Stage


  • light energy (from the sun) is converted into chemical energy in the form of ATP and NADPH with oxygen release as a byproduct

  • Photophosphorylation

    • turning ADP into ATP

  • NADP+ works as a universal electron carrier

    • captures high energy electrons and hydrogen ions (protons) during light dependent reactions

      • coverts it into NADPH

      • this then stores and transports that chemical energy to the Calvin Cycle to help synthesize sugars


Reaction

H2O + Light —> O2


Light-dependent reactions (photosynthesis reaction) (article) | Khan Academy


The Calvin Cycle


  • turns CO2 and energy from light dependent reactions into glucose inside of the Stroma

  • G3P (3 carbon compound) is the carbohydrate directly produced from the Calvin cycle

  • glucose has 6 carbons so it will take 6 turns of the CC to produce 1 glucose


Carbon Fixation

  • first step of the Calvin cycle and turns inorganic CO2 into organic compounds like carbohydrates

  • RuBisCo (an enzyme) attaches to inorganic CO2 to a RuBP (a 5 carbon molecule) to create a 6 carbon intermediate that then gets split into 2 3-carbon compounds (3-PGA)


Reduction

  • the reducing power of NADPH will donate electrons to the low energy acid 1,3-biosphophoglycerate to from G3P

    • essentially the electrons lost will go into creating the carbohydrate


Regeneration of RuBP

  • converting 3-carbon molecules (G3P) back into 5-carbon RuBP by using ATP

  • Sugar Shuffle

    • 5 G3P molecules are rearranged into 3 molecules of Ribulose 5-phosphate

    • Ribulose 5-phosphate kinase uses ATP to add a second phosphate group to each ribulose 5-phosphate


Reaction

CO2 —> Glucose


2 turns of the Calvin cycle = 1 glucose

Learn: The Calvin cycle (article) | Khan Academy


Photosystem

  • a large, multi-protein complex found int eh thylakoid membranes

  • absorbs sunlight and converts it into chemical energy

Photosystem II — Absorbs light at 680 nm

Photosystem I — Absorbs light at 700 nm

  • Red and Blue light are used for photosynthesis