Photosynthesis Summary Notes (AP Biology 2007-2008) PDF

AP Biology 2007-2008  Photosynthesis: Life from Light and Air AP Biology  Energy needs of life ▪ All life needs a constant input of energy ◆ Heterotrophs (Animals) ▪ get their energy from “eating others” consumers ⬥ eat food = other organisms =...

AP Biology 2007-2008  Photosynthesis: Life from Light and Air AP Biology  Energy needs of life ▪ All life needs a constant input of energy ◆ Heterotrophs (Animals) ▪ get their energy from “eating others” consumers ⬥ eat food = other organisms = organic molecules ▪ make energy through respiration ◆ Autotrophs (Plants) ▪ produce their own energy (from “self”) ▪ convert energy of sunlight producers ▪ build organic molecules (CHO) from CO2 ▪ make energy & synthesize sugars through AP Biology photosynthesis  How are they connected? Heterotrophs making energy & organic molecules from ingesting organic molecules glucose + oxygen → carbon + water + energy dioxide C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP oxidation = exergonic Where’s Autotrophs the making energy & organic molecules from light energy ATP? carbon + water + energy → glucose + oxygen dioxide 6CO2 + 6H2O + light → C6H12O6 + 6O2 energy AP Biology reduction = endergonic  Chloroplasts cross section absorb leaves of leaf sunlight & CO2 CO2 chloroplasts in plant cell chloroplasts chloroplast contain chlorophyll make AP Biology energy & sugar  chloroplast + + + + H+ H +H + H++ H H + +H H H Plant structure A T H H thylakoid P ▪ Chloroplasts ◆ double membrane outer inner ◆ stroma membrane membrane ▪ fluid-filled interior ◆ thylakoid sacs strom ◆ grana stacks a ▪ Thylakoid membrane thylakoi contains d granu m ◆ chlorophyll molecules ◆ electron transport chain ◆ ATP synthase ▪ H+ gradient built up within AP Biology thylakoid sac  Photosynthesis ▪ Light reactions ◆ light-dependent reactions ◆ energy conversion reactions ▪ convert solar energy to chemical energy ▪ ATP & NADPH It’s not the ▪ Calvin cycle Dark Reactions! ◆ light-independent reactions ◆ sugar building reactions ▪ uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6 AP Biology  chloroplast + thylakoid + + +H+H +H +H++ H H + +H H H H Light reactions A H+ H+H H +H+ H+ + H + + + + T H+H H H H ▪ Electron Transport Chain P ▪ like in cellular respiration ◆ proteins in organelle membrane ◆ electron acceptors ▪ NADPH ◆ proton (H+) gradient across inner membrane ▪ find the double membrane! ◆ ATP synthase enzyme AP Biology ETC of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP ◆ use electron carrier NADPH generates O2 AP Biology  ATP Synthase photosynthesis respiration sunlight breakdown of C6H12O6 H+ H+ H H + + + + H H H+ H+ ▪ moves the electrons ▪ runs the pump ▪ pumps the protons ▪ builds the gradient ▪ drives the flow of protons through ATP synthase ADP + Pi ▪ bonds Pi to ADP AT P ▪ generates the ATP H+ AP Biology … that evolution built  Pigments of photosynthesis How does this molecular structure fit its function? ▪ Chlorophylls & other pigments ◆ embedded in thylakoid membrane ◆ arranged in a “photosystem” ▪ collection of molecules AP Biology ◆ structure-function relationship  A Look at Light ▪ The spectrum of color V I B G Y O R AP Biology  Light: absorption spectra ▪ Photosynthesis gets energy by absorbing wavelengths of light ◆ chlorophyll a ▪ absorbs best in red & blue wavelengths & least in green ◆ accessory pigments with different structures absorb light of different wavelengths ▪ chlorophyll b, carotenoids, xanthophylls Why are plants green? AP Biology  ETC of Photosynthesis ▪ ETC uses light energy to produce ◆ ATP & NADPH ▪ go to Calvin cycle ▪ PS II absorbs light ◆ excited electron passes from chlorophyll to “primary electron acceptor” ◆ need to replace electron in chlorophyll ◆ enzyme extracts electrons from H2O & supplies them to chlorophyll ▪ splits H2O ▪ O combines with another O to form O2 ▪ O2 released to atmosphere ▪ and we breathe easier! AP Biology  Photosynthesis: The Calvin Cycle Life from Air AP Biology 2007-2008  Remember what it means to be a plant… ▪ Need to produce all organic molecules necessary for growth ◆ carbohydrates, lipids, proteins, nucleic acids ▪ Need to store chemical energy (ATP) produced from light reactions ◆ in a more stable form ◆ that can be moved around plant ◆ saved for a rainy day carbon + water + energy → glucose + oxygen dioxide AP Biology6CO2 + 6H2O + light → C H O + 6O energy 6 12 6 2  Light reactions ▪ Convert solar energy to chemical energy ATP ◆ ATP → energy ◆ NADPH → reducing power ▪ What can we do now? → → build stuff !! AP Biology photosynthesis  How is that helpful? ▪ Want to make C6H12O6 ◆ synthesis ◆ How? From what? What raw materials are available? CO 2 NADPH reduces carbon fixation CO2 NADP C6H12O6 NADP AP Biology  From CO2 → C6H12O6 ▪ CO2 has very little chemical energy ◆ fully oxidized ▪ C6H12O6 contains a lot of chemical energy ◆ highly reduced ▪ Synthesis = endergonic process ◆ put in a lot of energy ▪ Reduction of CO2 → C6H12O6 proceeds in many small uphill steps ◆ each catalyzed by a specific enzyme ◆ using energy stored in ATP & NADPH AP Biology  From Light reactions to Calvin cycle ▪ Calvin cycle ◆ chloroplast stroma ▪ Need products of light reactions to drive synthesis reactions strom ◆ ATP a ◆ NADPH AT P thylakoi d AP Biology  C C C Calvin cycle C C C C C 1C CO2 C C C C C 1. Carbon fixation 3. Regeneration C C C C C C C C C C C of RuBP RuBP 5C RuBisCo C C C C C C ribulose bisphosphate starch, sucrose, 3 ATP ribulose 6C C C C C C C cellulose bisphosphate & more 3 ADP carboxylase used 5C C C C C C C to make glyceraldehyde-3-P C C C glucose PGA 3C C C C G3P phosphoglycerate C C C C C C C C C C= C= C C C C 3C C C C C C C C C C 2. Reduction 6 ATP H H H | | | C C C 6 NADPH 6 ADP C– C– C | | | AP Biology H H H C C C 3C 6 NADP  RuBisCo ▪ Enzyme which fixes carbon from air ◆ ribulose bisphosphate carboxylase ◆ the most important enzyme in the world! ▪ it makes life out of air! ◆ definitely the most abundant enzyme It’s not I’m green easy with envy! being green! AP Biology  Photosynthesis summary ▪ Light reactions ◆ produced ATP ◆ produced NADPH ◆ consumed H2O ◆ produced O2 as byproduct ▪ Calvin cycle ◆ consumed CO2 ◆ produced G3P (sugar) ◆ regenerated ADP ◆ regenerated NADP ADP NADP AP Biology