1. Energy in Cells
Some molecules act as energy carrier molecules (receive energy in the form of electrons and transfer them to some other part of the cell)
Phosphate groups commonly serve as energy carriers (they resemble hydrogen ions in this manner)
Phosphorylation is the addition of a phosphate group to a molecule, thereby reducing the target molecule (increasing its energy) and reducing the original carrier of the phosphate group (decreasing its energy)
Phosphate group

2. Energy in Cells Common Energy Carrier Molecules:
ATP  ADP + Pi + energy (e-) ADP + Pi + e-  ATP
FADH2  FAD + 2H+ + 2e FAD + 2H + 2e-  FADH2
NADH  NAD+ + H+ + 2e NAD+ + H + 2e-  NADH

3. Photosynthesis KNOW THIS SLIDE!
Photosynthesis is the conversion of energy from light into chemical energy stored in glycosidic bonds
carbon dioxide
water
glucose
oxygen
6H20 + 6CO2 + light  C6H12O6 + 6O2
Granum
Light-independent (dark) reactions

4. energy carrier molecules
Photosynthesis
Chloroplasts (plant cells and photosynthetic protists)
Have double membrane (inner and outer)
Grana (stacks of thylakoids) – membrane of these is where light reactions of photosynthesis occur
Chlorophyll – light-absorbing pigment in thylakoids
Stroma – fluid that fills chloroplasts surrounding the grana – where light independent reactions occur (also known as the Dark Reactions or Calvin Cycle)
Thylakoid
Stroma
(Calvin Cycle)
energy carrier molecules

5. Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI
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Light-Dependent Reactions of Photosynthesis (Occur in the grana via proteins embedded in the thylakoid membranes)
Photosystem II:
Energy from light is absorbed by chlorophyll molecules in the Photosystem II protein complex embedded in the membrane of the thylakoids
the energy is transferred to electrons taken from breaking water (H2O) into 2 H+ ions plus one oxygen atom
two of these oxygen atoms later combine to form O2 gas which is then released into the air

6. Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI
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Light-Dependent Reactions of Photosynthesis (Occur in the grana via proteins embedded in the thylakoid membranes)
2. Electron Transport Chain:
Excited electrons are passed from protein to protein in a group of proteins called the electron transport chain (ETC)
some of the energy of the electrons is used by the ETC to pump H+ ions into the thylakoid creating a concentration gradient in which the inside of the thylakoid becomes positively charged
The electrons are less energetic when they leave the ETC than when the entered it

7. Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI
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Light-Dependent Reactions of Photosynthesis (Occur in the grana via proteins embedded in the thylakoid membranes)
3. Photosystem I:
The electrons are re-energized by more light captured by chlorophyll in the Photosystem I protein complex
These electrons and their energy are then used to add phosphate groups to NADH+ molecules in order to create the energy carrier molecules NADPH

8. Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI
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Light-Dependent Reactions of Photosynthesis (Occur in the grana via proteins embedded in the thylakoid membranes)
4. ATP Synthase:
H+ ions trapped inside the positively charged thylakoid want to get away
ATP Synthase proteins embedded in the membrane provide a passage for the H+ ions to escape, and as they do, they cause an inner part of the protein to spin
Energy from this spinning protein is used to add phosphate groups to ADP molecules in order to create the energy carrier molecules ATP (much in the same way that water or wind turns turbines to create energy)

9. Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI
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Light-Dependent Reactions of Photosynthesis (Occur in the grana via proteins embedded in the thylakoid membranes)
The NADH and ATP energy carrier molecules move to the Calvin Cycle in the Stroma
where their energy is used to build sugars.

10. Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI
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Light-Dependent Reactions of Photosynthesis (Occur in the grana via proteins embedded in the thylakoid membranes)
Light excites the electrons in chlorophyll (photons are converted into chemical energy)
Excited electrons are passed down electron transport chain (ETC) (e- are replaced with e- from splitting water, which is why O2 is released)
Electron transport chain pumps protons (H+) into thylakoid - H+ ions from splitting water are also released into thylakoid – results in concentration gradient (+ charge on one side)
Energy is captured in carrier molecules:
NADPH is synthesized at third ETC protein using energy from the excited e- passed down the Electron Transport Chain in addition to another photon from light)
ATP is synthesized using energy from H+ leaving thylakoid through ATP synthase
Carrier molecules (NADPH and ATP) move to stroma to power carbohydrate synthesis (building sugars) via the Calvin cycle (dark reactions) H+
O2 emitted from plants
Photon of light
NADP  NADPH
Photon of light
Photon of light e-
ADP  ATP H+ e- e- e-
H+ pumped in and from splitting water H+
2H+
H2O
½ O2
2e- +

11. Photosynthesis Dark Reactions of Photosynthesis
(Occur in the stroma via the Calvin cycle using NADPH and ATP from the light reactions)
A CO2 molecule enters and its carbon is stripped off and rearranged with a 5-carbon molecule to produce a 6-carbon molecule
The 6-carbon molecule is unstable and quickly rearranges to form two 3-carbon molecules
Energy is input from ATP and then NADPH to rearrange the 3-carbon molecule into a new, more energetic 3-carbon sugar molecule
Five of these high-energy 3-carbon sugar molecules are combined and rearranged to create:
Three of the 3-carbon molecules that were used to start the process (these are recycled)
One 6-carbon glucose molecule