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Photosynthesis

Photosynthesis stores the energy from sunlight in organic molecules like glucose.

  • Formula:  Sunlight + Water + Carbon Dioxide --> Glucose + Oxygen

  • Occurs in chloroplasts of plant cells and some protists

  • Takes place in two stages:

    • Light Reactions - chlorophyll and other pigments capture energy from specific wavelengths of light to make ATP

    • Calvin Cycle - Energy from the ATP is used to "fix" carbon to organic molecules which can be converted into glucose.

Chloroplasts

Light Reactions

Chloroplast and Light Reactions.png

Light Reactions capture energy from the sun and use it to make ATP.

  • Water molecules are split to release Hydrogen ions, electrons, and oxygen.

  • Chlorophyll absorbs energy mostly from red and blue wavelengths of light, green wavelengths are reflected (plants are green)

  • Chlorophyll boosts the energy of the electrons which then pass through an electron transport chain that pumps the hydrogen ions into the thylakoid.

  • As they flow out, they pass through ATP Synthase which creates ATP

  • Oxygen is released as a waste product

Chloroplasts are the organelle that carries on the process of photosynthesis

  • They are commonly found on the outside of cells in the mesophyll (middle-leaf)

  • Stroma - fluid inside of a chloroplast

  • Thylakoids - flat hollow sacs that contain photosystems and ATP Synthase

  • Grana - stacks of thylakoids

Calvin Cycle

The Calvin Cycle uses the energy from the light reactions to attach inorganic carbon dioxide to existing organic molecules.

  • When enough carbon has been added,  molecules of G3P (3 carbon molecule) are broken off.

  • 2 G3P molecules can be combined to make glucose

Calvin Cycle.png
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