Light + 6 CO2 + 6 H2O

C6 H12 O6 + 6 O2 + Heat
**Remember to look for the flow of hydrogens.
Oxidized = lose electrons
Reduced = gain electrons
For both, hydrogen will carry these electrons
LEO the lion says GER
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Reactants
 Light = Original source of energy
 CO2 = gains hydrogens to become glucose (sugar)
 H20 = break water to release hydrogens to provide electrons, release oxygen as byproduct
Products
 C6H12O6 (glucose) = sugar (food).


O2 = byproduct (not used)
Heat = imperfect energy conversion (2 nd law of thermodynamics)
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Method of converting sun’s energy into chemical energy usable by cells

 Autotrophs : self feeders, organisms capable of making their own food
 Photoautotrophs
: use sun’s energy e.g. plants photosynthesis-makes organic compounds
(glucose) from light
 Chemoautotrophs : use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane
**** Photosynthesis does not give plants energy. It provides them with the food (glucose) that mitochondria can then use to create energy (ATP).
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 Photosynthesis takes place in specialized structures inside plant cells called chloroplasts . Chloroplasts are located in the leaves of plants (so that’s where photosynthesis occurs).
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 Chlorophyll IS NOT the only light absorbing pigment in plants. It is just the most abundant
(which is why chloroplasts (and thus plants) are green).
 Different pigments are responsible for absorbing different wavelengths of light. Remember
ROYGBIV.
 Pigments include chlorophyll a, chlorophyll b, carotenoid, among others.
 If chlorophyll are green, what colors of light do they absorb?
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Overall Reaction
**** Cellular Respiration Equation is exact opposite of photosynthesis equation (minus the sunlight)
6CO
2
+ 6 H
2
O + light energy → C
6
H
12
O
6
+ 6O
2





Carbohydrate made is glucose
Water is split as a source of electrons from hydrogen atoms releasing O
2 byproduct as a
Electrons increase potential energy when moved from water to sugar therefore energy is required
Why does it take 6 carbon dioxide and 6 waters to make 1 glucose (and release 6 oxygen)??
****To remember this equation, think “what does a plant need and what does it make”

**** It “needs” CO
2 to turn into glucose, water for electrons, and sunlight.
Energy from sunlight breaks water. H + are taken from water and given to
CO
2
.

**** It makes glucose for food and oxygen as a byproduct (waste). Adding
H + to CO
2
12 generates glucose and taking H+ from water generates oxygen.

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Chlorophyll absorbs the blue but reflects the green.
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Light Reactions Overview:
***H
2
0 + Light energy O
2
+ ATP + NADPH
**This part makes the “batteries” (ATP and NADPH) for making sugar in the next step
**** Note that this is where we use water and light as well as make oxygen. What other parts of the photosynthesis equation are not used / made here (so they have to be in next step)?
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****
ELECTRON TRANSPORT CHAIN pumps H+ ions into the thylakoid space and CHEMIOSMOSIS uses this to make ATP using ATP Synthetase
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Pumping the H+ (protons) into a confined space to build up potential energy.
See the similarity in structure and function?
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Calvin Cycle (light independent or “dark” reactions) – occurs in stroma




ATP and NADPH generated in light reactions used to fuel the reactions which take CO
2 the carbons into glucose.
and break it apart, then reassemble
Called carbon fixation : taking carbon from an inorganic molecule (atmospheric CO
2
) and making an organic molecule out of it (glucose)
**** Basically, Calvin Cycle uses products from light reactions to make glucose.
**** Even though this is called the “dark reactions” they still occur mostly during the day. Why?
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Calvin Cycle Overview:
**** 6 CO
2
+ ATP + NADPH C
6
H
12
O
6
(glucose) + ADP (P)
+ NADP +
**** Note that ATP and NADPH are not in overall equation because they are constantly recycled (ATP ADP + P and NADPH NADP+)
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