BIOL 1441 1st Edition Lecture 18 Outline of Last Lecture I. Hydrogen gradientII. ATP productionIII. FermentationIV. Fermentation vs. cellular respirationV. Facultative anaerobesVI. Versatility of catabolismVII. PhotosynthesisVIII. Plant anatomyIX. Redox reactionX. Respiration vs. photosynthesisXI. Sunlight Outline of Current Lecture I. Light propertiesII. Photosynthetic pigmentsIII. Spectrophotometer IV. Accessory pigmentsV. Excitation of chlorophyllVI. PhotosystemsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VII. Light reactionVIII. Linear electron flowIX. Calvin cycle-dark rxnCurrent LectureI. Light Propertiesa. Reflection- bounces backi. This is the color you see!b. Transmission- passes through (microscope)c. Absorption- used as energyi. Black objects reflect 0 light, gain heat faster than white objects (reflects all light)ii. Comes out of molecule at a lower energy leveliii. Fluorescence: when light comes out as a lower wavelength and it releasesa photon1. seeing visible light/UV light togetherd. Refraction- bending lightII. Photosynthetic Pigmentsa. Pigments absorb visible lightb. Different pigments absorb different wavelengthsc. Wavelengths not absorbed are reflected or transmittedd. Leaves appear green-chlorophyll reflects & transmits green lighti. Means it doesn’t use green wavelengthIII. Spectrophotometera. Measures pigment’s ability to absorb various wavelengths b. Sends light through pigments & measures the fraction of light transmitted at each wavelengthIV. Accessory Pigmentsa. Chlorophyll a- main photosynthetic pigmentb. Chlorophyll b- olive greenc. Carotenoids- yellow/orange, absorb violet & blue-green lighti. In the fall when there is not as much sunlight there is not as much photosynthesis happening. Carotenoids start breaking down pigments and that is why you see yellow/orange colored leavesV. Excitation of Chlorophylla. Pigment absorbs light- ground state to excited state (unstable)i. Cant stay in excited state for very longb. Molecule’s electron elevated to an orbital with more potential energy (further from nucleus)c. Photons absorbed are those whose energy is exactly equal to the energy difference between the ground state and the excited statei. “exact change”has to be the exact wavelengthd. Varies from one molecule to anothere. Particular compound only absorbs photons corresponding to specific wavelengths- unique absorption spectrumVI. Photosystems: where chlorophyll absorbs photonsa. Thylakoid membrane chlorophyll molecules organized along with other organic molecules & proteinsb. Reaction center surrounded by light-harvesting complexesc. PASSES A PHOTON OF LIGHTd. Rxn center- 2 chlorophyll a moleculesi. Chlorophyll a special molecular environment- enabling them to use energy from light to boost electrons to a higher energy level & to transfer itii. Primary electron acceptor- accepts excited electron from chlorophyll a1. Oxidized: chlorophyll ae. Light-harvesting complexes- pigment molecules bound to proteinsi. Various pigments- allows photosystem to absorb wider range of wavelengthsii. Pigment absorb photon- transfer the energy (photon) from pigment molecule to pigment molecule, then to chlorophyll a molecules in rxn centerf. Two types of photosystems in thylakoid membranei. Photosystem I & II (PS I & PS II)ii. Both contain a pair of chlorophyll a moleculesg. Photosystem II functions 1 st in the light reaction (P680)i. Numbers reflect order of discoveryii. Absorbs wavelength of 680 nm h. Photosystem I -absorbs wavelength of 700 nm (P700)i. Work together- use light energy to generate ATP & NADPHi. 2 electron transport chains in between Photosystem I and II1. First ETC makes: ATP2. Second ETC makes: NADPHVII. Light Reaction- Redoxa. 1st step of light rxn’s: solar-powered transfer of an electron from chlorophyll a to primary electron acceptorb. As soon as chlorophyll electron excites to a higher energy level- primary electron acceptor captures it- redox rxnc. Chemiosmosis –Chloroplasts & Mitochondriai. Both generate ATP by chemiosmosis- different energy sources1. Mitochondria- transfer chemical energy from food to ATP2. Chloroplasts- transform light energy into the chemical energy (ATP)ii. ETC transform redox energy to a proton-motive force (drop in free energy from e- transfer) and (proton gradient)iii. ATP synthase in membrane- phosphorylates ADPiv. Oxidative phosphorylation- high energy electrons dropped down ETC, extracted from organic molecules (food!)v. Photophosphorylation- water is the source of electrons, light energy drives electrons from water to top ETCvi. Spatial organization of chemiosmosis differs in chloroplasts and mitochondriaVIII. Linear Electron Flowa. Step 1: (photosystem II)i. Photon of light strikes pigment, boosts electro to higher energy level(excited)redox reactionb. Step 2: (photosystem II)i. Photoexcited electron is transferred from excited P680 to primary electron acceptor1. P680P680+ oxidized2. P680=reduced state3. P680+ = oxidized statec. Step 3: (photosystem II)i. Enzyme catalyzes splitting of H2O into two electrons, 2 H+, O1. Oxygen becomes the air we breath2. H2O REDUCES P680+ to P6803. Oxidizing agent=P680+d. Step 4: (photosystem II)i. Photoexcited electron passes fro primary electron acceptor of PS II to PS I through the ETCe. Step 5: (Photosystem II):i. Exergonic fall of electrons to lower energy level provides energy for ATP sytnthesis1. Just like in respiration-move electrons down to a more electronegative molecule-drop in free energyii. PUMPS H+ INTO THYLAKOID SPACE, DIFFUSES INTO STROMAf. Step 6: (photosystem I)i. P700P700+1. Accepts electrons from bottom of ETC from PS II2. FINAL ELECTRON ACCEPTOR IN 1ST ETC IS P700+3. P700+ IS REDUCED BY FIRST ETCg. Step 7: (photosystem I)i. NO proton gradientii. NO ATP producedh. Step 8: (photosystem I)i. NADP+ reducase1. Reduces NADP+  NADPHa. Gives it electronsii. FINAL ELECTRON ACCEPTOR- NADP+IX. Calvin Cycle- dark rxna. Anabolic rxn- building molecules, requires energyi. Builds sugar using ATP & NADPH (from light rxn)b. Carbon enters the cycle as CO2 i. CO2 fees in one at a timec. Leaves as glyceraldehyde-3-phosphate (G3P)d. For net synthesis of one G3P, cycle must take place three times, “fixing” three molecules of CO2i. Fixing=inorganic  organice. Sugar produced is not glucose!f. Produces