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Photosynthesis

Light

6 H2O + 6 CO2 ----> C6H12O6 + 6 O2water carbon dioxide sugar oxygen

A. PhotosynthesisHistory

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1. Jan VonHelmont (1577-1644)Experiment: Hemassed a seedling andsoil, then planted theseedling. He took goodcare of it for 5 years.Then massed the treeand soil.Results: Soil wasabout the same. Treegained 75 kg.Conclusion: The masscame from the water.

2. Joseph Priestly (1733-1804)a. Experiment - He put a lit candle in a bell jar. It went

out! (duh!) He put in a mint plant for awhile - thecandle could be relit!

b. Conclusion - The fire used up “something” in the airthe candle needed to burn. Plants make that“something.”

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3. Jan Ingenhousz (1730-1799)

Experimented withplantsConclusion - Plantsonly make the“something” whenthey are exposed tolight.

Look at Equation: what’s missing?Light

6 H2O + 6 CO2 ----> C6H12O6 + 6 O2water carbon dioxide sugar oxygen

VanHelmont said water was responsible for themass (perhaps carbohydrate?)Priestly said that “something” (oxygen) wasmade by plantsIngenhousz said light was necessary

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Pigments & LightWhite light is made of allthe colors of thespectrum.Red and Blue areabsorbed the best.Blue light is absorbed (itis used-we don’t see it).Leaves look green, thelight is reflected (notused).

Absorption of Light by Chlorophyll

Energy-Storing Compounds

Adenosine triphosphate(ATP) is the form ofenergy the cell can use;“energy currency of thecell”Three phosphates with2 high-energy bondsbetween them.Mitochondria make ATP

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The Process:Break the high-energy phosphatebond in ATP:release energy forthe cell to use!

Break the high-energy phosphatebond in ADP:release energy forthe cell to use!

MAKE a bond toSTORE energy

Photosynthesis

Light

6 H2O + 6 CO2 ----> C6H12O6 + 6 O2water carbon dioxide sugar oxygen