Photosynthesis

CO2 + H2O chlorophyllight-> (CH2O)n +O2

-Photosynthesis is valuable -

1. oxygen in the air comes from photosynthesis

2. All our food comes directly or indirectly from photosynthesis

-Light - show light scale for visible light

-shorter wavelengths have to much energy (nuclear radiation)

-longer wavelengths don't have enough energy (microwaves, radio)

-Pigments - show chart and reason they are colored (absorbing light)

-chlorophyll from chart

-carotenoid

-show leaf-

-epidermis - waxy waterproof surface (cuticle) prevents loss of water vapor.

-somata - lower openings of leaf to permit CO2 to enter

-Palisade cells - closely packed columnar cells, just below upper epidermis

-spongy layer - loosely arranged cells with air spaces between

-veins - vascular tissue - carry water and carbohydrates to where they need to be.

-Chloroplasts -

-Thylakoid membrane - trap and use light energy

-Thylakoids in stacks called grana

-Thylakoids surrounded by protein rich solution that contains enzymes to make carbohydrates - called STROMA

Photosynthesis is in two steps

1. Light reaction - energy capturing stage. Need light to run

-Occurs in the thylakoid

-Photons - packages of light

-every photon produces 1 ATP and 1 NADH

-ATP formed by splitting of water forming H+ which can form ATP

2. Dark Reaction (Calvin cycle or C3 cycle)- occurs without light, but from energy received from light reaction.

-Start 5 carbon chain to two 3 carbon chains by using 1 CO2(split) uses 2 ATP and 2 NADPH = 1 ATP

-some e carbon form 6 carbon

-some synthesize amino acids

-some form back to 5 carbon

-Ecological aspects

-stomates let CO2 in but also let H2O out

-some plants have evolved to carry on photosynthesis more rapidly even at low CO2 levels because they can trap CO2.

-trap CO2 on 4 carbon compound

-C4 pathway

-C4 pathway uses 5 ATP instead of 3 ATP

-At high temperatures C4 plants can photosynthesize faster.

-Sacrifices efficiency for speed

-evolved in warm sunny areas (corn)

-C3 plants (most plants) potatoes, flowers

-variation of C4 is CAM (Crassulacean acid metabolism)

-cacti and other succulent plants (alovera)

-Close stomates in day and open them at night

-CO2 becomes trapped in the acids

-not as efficient, but essential iÔ

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