Transcript Document
Photosynthesis: Life from Light AP Biology Energy needs of life All life needs a constant input of energy Heterotrophs get their energy from “eating others” consumers of other organisms consume organic molecules Autotrophs get their energy from “self” get their energy from sunlight use light energy to synthesize organic molecules AP Biology How are they connected? Heterotrophs making energy & organic molecules from ingesting organic molecules glucose + oxygen carbon + water + energy dioxide C6H12O6 + 6O2 6CO2 + 6H2O + ATP Autotrophs making energy & organic molecules from light energy carbon + water + energy glucose + oxygen dioxide 6CO2 + 6H2O + light C6H12O6 + 6O2 energy AP Biology 2005-2006 Energy cycle sun Photosynthesis CO2 H 2O glucose Cellular Respiration The Great Circle of Life! AP Biology Where’s Mufasa? ATP O2 What does it mean to be a plant Need to… collect light energy transform it into chemical energy store light energy in a stable form to be moved around the plant & also saved for a rainy day need to get building block atoms from the environment C,H,O,N,P,S produce all organic molecules needed for growth carbohydrates, proteins, lipids, nucleic acids AP Biology Plant structure Obtaining raw materials sunlight leaves = solar collectors CO2 stomates = gas exchange regulation Found under leaves H2O uptake from roots nutrients uptake from roots AP Biology 2005-2006 Plant structure Chloroplasts double membrane stroma thylakoid sacs grana stacks Chlorophyll & ETC in thylakoid membrane H+ gradient built up within thylakoid sac H+ AP Biology + + H + H H+ + H H + H+ H+ H+ + H H Pigments of photosynthesis chlorophyll & accessory Why does this structure make sense? pigments “photosystem” embedded in thylakoid membrane structure function AP Biology 2005-2006 Light: absorption spectra Photosynthesis performs work only with absorbed wavelengths of light AP Biology chlorophyll a — the dominant pigment — absorbs best in red & blue wavelengths & least in green other pigments with different structures have different absorption spectra Photosystems Photosystems collections of chlorophyll molecules 2 photosystems in thylakoid membrane act as light-gathering “antenna complex” Photosystem II chlorophyll a P680 = absorbs 680nm wavelength red light Photosystem I chlorophyll b P700 = absorbs 700nm wavelength red light AP Biology Transfer of Electrons in PSII & PSI In both PSII and PSI, the energy from the excited e- pumps H+ into the thylakoid as it moves through the ETC. Electrons from PSII are transferred to PSI. After electrons have moved through PSI, an intermediary molecule (embedded in the membrane and adjacent to PSI) transfers the e- to NADP+. A H+ is attracted to this molecule and NADPH is formed. AP Biology Chemiosmosis in Photosynthesis **(similar in Cell Respiration) proton (H+) gradient across inner membrane drive ATP formation ATP synthase enzyme AP Biology 2005-2006 Summary of the LDR PS II absorbs light excited electron passes from chlorophyll to “primary electron acceptor” at the REACTION CENTER. splits H2O (Photolysis!!) O2 released to atmosphere PS I absorbs light Produces NADPH (stored energy) which will be used by the Calvin cycle Chemiosmosis produces ATP from light energy ATP will be used by the Calvin Cycle AP Biology ETC of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP AP Biology split H2O use electron carrier NADPH 2 Photosystems Light reactions elevate electrons in 2 steps (PS II & PS I) PS II helps generate energy as ATP (H+ pumps) PS I generates reducing power as NADPH This shows Noncyclic photophosphorylation. AP Biology ETC of Photosynthesis AP Biology ETC of Photosynthesis AP Biology Cyclic photophosphorylation If PS I can’t pass electron to NADP, it cycles back to PS II & makes more ATP, but no NADPH AP Biology coordinates light reactions to Calvin cycle Calvin cycle uses more ATP than NADPH Do Now: Light Reactions Summary Questions Where did the energy come from? Where did the H2O come from? Where did the electrons come from? Where did the O2 come from? Where did the H+ come from? Where did the ATP come from? Where did the O2 go? What will the ATP be used for? What will the NADPH be used for? AP Biology Calvin Cycle Overview Calvin cycle uses chemical energy (NADPH & ATP) to reduce CO2 to build C6H12O6 (sugars) AP Biology From Light reactions to Calvin cycle Calvin cycle Occurs in the stroma of the chloroplast Need products of light reactions to drive synthesis reactions ATP NADPH AP Biology From CO2 C6H12O6 CO2 has very little chemical energy fully oxidized C6H12O6 contains a lot of chemical energy reduced endergonic Reduction of CO2 C6H12O6 proceeds in many small uphill steps each catalyzed by specific enzyme using energy stored in ATP & NADPH AP Biology Calvin cycle 1C ribulose bisphosphate 3. Regeneration RuBP 3 ATP PGAL to make glucose 5C 1. Carbon fixation Rubisco ribulose bisphosphate carboxylase 3 ADP PGAL sucrose cellulose etc. CO2 6C unstable intermediate 2x 3C 3C x2 PGA 2. Reduction 6 ATP 6 NADPH 6 NADP AP Biology 2x 3C 6 ADP Rubisco Enzyme which fixes carbon from atmosphere ribulose bisphosphate carboxylase the most important enzyme in the world! it makes life out of air! AP Biology definitely the most abundant enzyme Calvin cycle PGAL end product of Calvin cycle energy rich sugar 3 carbon compound “C3 photosynthesis” PGAL important intermediate PGAL AP Biology glucose carbohydrates lipids amino acids nucleic acids Photosynthesis summary Light reactions produced ATP produced NADPH consumed H2O produced O2 as byproduct Calvin cycle consumed CO2 produced PGAL regenerated ADP regenerated NADP AP Biology Summary of photosynthesis 6CO2 + 6H2O + light C6H12O6 + 6O2 energy Where did the CO2 come from? Where did the CO2 go? Where did the H2O come from? Where did the H2O go? Where did the energy come from? What’s the energy used for? What will the C6H12O6 be used for? Where did the O2 come from? Where will the O2 go? What else is involved that is not listed in this equation? AP Biology 2005-2006