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

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

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

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

Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI Use this website to Help you! 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

Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI Use this website to Help you! 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

Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI Use this website to Help you! 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

Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI Use this website to Help you! 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)

Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI Use this website to Help you! 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.

Photosynthesis http://www.youtube.com/watch?v=hj_WKgnL6MI Use this website to Help you! 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- +

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