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

• 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)

Energy in Cells

Phosphate group

• 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

Energy in Cells

Photosynthesis is the conversion of energy from light into chemical energy stored in glycosidic bonds

6H20 + 6CO2 + light C6H12O6 + 6O2

Light-independent (dark) reactions

glucose

Granum

oxygencarbon dioxidewater

Photosynthesis KNOW THIS SLIDE!

• 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)

PhotosynthesisChloroplasts (plant cells and photosynthetic protists)

(Calvin Cycle)

Thylakoid Stroma

energy carrier

molecules

Light-Dependent Reactions of Photosynthesis(Occur in the grana via proteins embedded in the thylakoid membranes)

1. 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

Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI

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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




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




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)




The NADH and ATP energy carrier molecules move to the Calvin Cycle in the Stroma where their energy is used to build sugars.




1. Light excites the electrons in chlorophyll (photons are converted into chemical energy)2. Excited electrons are passed down electron transport chain (ETC)

(e- are replaced with e- from splitting water, which is why O2 is released)3. 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) 4. 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 5. Carrier molecules (NADPH and ATP) move to stroma to power carbohydrate synthesis

(building sugars) via the Calvin cycle (dark reactions)


e-

Photon of lightPhoton of light

e-

H+

2H+ H2O½ O22e- ++

NADP NADPHPhoton of light

e-

e-

H+

ADP ATP

O2 emitted from plants

H+ pumped in and from splitting waterH+

H+H+

H+ H+H+ H+ H+ H+ H+H+

H+


• Dark Reactions of Photosynthesis(Occur in the stroma via the Calvin cycle using NADPH and ATP from the light reactions)

1. A CO2 molecule enters and its carbon is stripped off and rearranged with a 5-carbon molecule to produce a 6-carbon molecule

2. The 6-carbon molecule is unstable and quickly rearranges to form two 3-carbon molecules

3. Energy is input from ATP and then NADPH to rearrange the 3-carbon molecule into a new, more energetic 3-carbon sugar molecule

4. 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

Photosynthesis

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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