AP Biology
AP Biology Photosynthesis: Life from Light and Air
AP Biology The energy needs of life consumers producers All life needs a constant input of energy Heterotrophs (Animals) get their energy from “eating others” eat food (other organisms) = organic molecules make energy through respiration Autotrophs (Plants) produce their own energy (from “self”) convert energy of sunlight build organic molecules (CHO) from CO 2 make energy & synthesize sugars through photosynthesis. Make additional ATP through respiration.
AP Biology How are they connected? glucose + oxygen carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP +++ Heterotrophs + water + energy glucose + oxygen carbon dioxide 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy +++ Autotrophs making energy & organic molecules from light energy making energy & organic molecules from ingesting organic molecules oxidation = exergonic reduction = endergonic But remember autotrophs do cell resp. also!
AP Biology N P K … H2OH2O 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 or stored need to get building block atoms from the environment C,H,O,N,P,K,S,Mg produce all organic molecules needed for growth carbohydrates, proteins, lipids, nucleic acids ATP glucose CO 2
AP Biology Plant structure Obtaining raw materials sunlight leaves = solar collectors CO 2 stomates = gas exchange H2OH2O uptake from roots nutrients N, P, K, S, Mg, Fe… uptake from roots
AP Biology stomate transpiration gas exchange
AP Biology Chloroplasts chloroplasts in plant cell cross section of leaf leaves chloroplast absorb sunlight & CO 2 make energy & sugar chloroplasts contain chlorophyll CO 2
AP Biology Chloroplasts double membrane stroma - fluid-filled interior thylakoid grana stacks Thylakoid membrane contains chlorophyll molecules electron transport chain ATP synthase H + gradient built up in thylakoid lumen Plant structure outer membrane inner membrane thylakoid granum stroma
AP Biology Pigments of photosynthesis Chlorophylls & other pigments embedded in thylakoid membrane arranged in a “photosystem” collection of molecules
AP Biology Light The spectrum of color ROYGBIV
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 Photosynthesis 1. Light Reactions light-dependent reactions energy conversion reactions convert solar energy to chemical energy (ATP & NADPH) 2. Calvin Cycle light-independent reactions sugar building reactions uses chemical energy (ATP & NADPH) to reduce CO 2 & synthesize C 6 H 12 O 6 It ’ s not the Dark Reactions!
AP Biology Photosynthesis: The Light Reactions
AP Biology Electron Transport Chain like in cellular respiration proteins in organelle membrane electron acceptors NADPH proton (H + ) gradient across inner membrane ATP synthase enzyme Light reactions H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP thylakoid chloroplast
AP Biology Mitochondria transfer chemical energy from food molecules into chemical energy of ATP use electron carrier NADH ETC of Respiration generates H 2 O
AP Biology ETC of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP use electron carrier NADPH generates O 2
AP Biology Generating ATP moves the electrons runs the pump pumps the protons builds the gradient drives the flow of protons through ATP synthase bonds P i to ADP generates the ATP sunlightbreakdown of C 6 H 12 O 6 respirationphotosynthesis H+H+ ADP + P i H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP
AP Biology Photosystems 2 photosystems in thylakoid membrane collections of chlorophyll molecules act as light-gathering molecules Photosystem II P 680 chlorophyll = absorbs 680nm wavelength red light Photosystem I P 700 chlorophyll= absorbs 700nm wavelength red light photosystem
AP Biology ETC of Photosynthesis Photosystem IIPhotosystem I
AP Biology ETC of Photosynthesis
AP Biology 1 ETC of Photosynthesis e e sun Photosystem II P680
AP Biology 1 2 ETC of Photosynthesis Photosystem II P680 O HH H H e e e-e- e-e- H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP thylakoid chloroplast H+H+ +H+H O O Plants SPLIT water! fill the e – vacancy get pumped into tylakoid lumen to form H+ gradient e e
AP Biology 1 2 H+H+ H+H+ 3 4 H+H+ ADP + P i H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ e e e e ATP to Calvin Cycle energy to build carbohydrates H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP thylakoid chloroplast Photosystem II P680 ETC of Photosynthesis ATP
AP Biology e e e e sun 5 Photosystem II P680 Photosystem I P700 e e ETC of Photosynthesis e e fill the e – vacancy
AP Biology 6 electron carrier e e e e 5 sun NADPH to Calvin Cycle Photosystem II P680 Photosystem I P700 ETC of Photosynthesis
AP Biology split H 2 O ETC of Photosynthesis O ATP to Calvin Cycle H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ e e e e sun
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 H 2 O & supplies them to chlorophyll splits H 2 O O combines with another O to form O 2 O 2 released to atmosphere
AP Biology 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy +++ Experimental evidence Where does the O 2 come from? Use radioactive tracer = O 18 6CO 2 6H 2 O C 6 H 12 O 6 6O26O2 light energy +++ Experiment 1 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy +++ Experiment 2 Proved O 2 came from H 2 O not CO 2 = plants split H 2 O!
AP Biology Non-Cyclic Electron Transport Light reactions elevate electrons in 2 steps (PS II & PS I) PS II generates energy as ATP PS I generates reducing power as NADPH ATP
AP Biology Non-Cyclic Electron Transport
AP Biology Cyclic Electron Transport If PS I can’t pass electron to NADP…it cycles back to PS II & makes more ATP, but no NADPH coordinates light reactions to Calvin cycle Calvin cycle uses more ATP than NADPH ATP
AP Biology Cyclic Electron Transport
AP Biology Non-Cyclic Electron Transport (Photophosphorylation) NONcyclic photophosphorylation ATP NADP
AP Biology Cyclic Electron Transport (Photophosphorylation) cyclic photophosphorylation ATP
AP Biology Characteristics of the Light Reactions 1. Energy from light is used to split water into H and O. 2. O 2 is given off as a waste product and exits through stomata. 3. Electron transport chain creates H + gradient that is used to make ATP (for later use in Calvin Cycle). 4. H and electrons are carried by NADPH to the Calvin Cycle.
AP Biology Photosynthesis: The Calvin Cycle
AP Biology The Calvin Cycle Whoops! Wrong Calvin… 1950s | 1961
AP Biology 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 + water + energy glucose + oxygen carbon dioxide 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy +++
AP Biology Light reactions Convert solar energy to chemical energy ATP NADPH What can we do now? energy reducing power build stuff !! photosynthesis ATP
AP Biology How is that helpful? Want to make C 6 H 12 O 6 synthesis How? From what? What raw materials are available? CO 2 C 6 H 12 O 6 NADPH NADP reduces CO 2 carbon fixation NADP
AP Biology From CO 2 C 6 H 12 O 6 CO 2 has very little chemical energy fully oxidized C 6 H 12 O 6 contains a lot of chemical energy highly reduced Synthesis (anabolic) = endergonic put in a lot of energy Reduction of CO 2 C 6 H 12 O 6 proceeds in many small uphill steps each catalyzed by a specific enzyme using energy stored in ATP & NADPH made from the light reactions
AP Biology From Light Reactions to Calvin Cycle Calvin cycle occurs in the chloroplast stroma Need products of light reactions to drive synthesis reactions ATP NADPH stroma thylakoid ATP
AP Biology starch, sucrose, cellulose & more 1C CO 2 Calvin Cycle 5C RuBP 3C RuBisCo 1. Carbon fixation 2. Reduction 3. Regeneration of RuBP ribulose 1,5-bisphosphate ribulose bisphosphate carboxylase 6 NADP 6 NADPH 6 ADP 6 ATP 3 ADP 3 ATP used to make glucose 3C G3P glyceraldehyde 3-phosphate CCCCCCCCCCCCCCC 6C CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC 3PG 3-phosphoglycerate CCCCCCCCCCCCCCCCCCCCC C C C CCC == | H | H | H | H | H | H CCC –– 5C compare this diagram with 6.21
AP Biology In Principles of Life, PGA is known as 3PG. In Principles of Life, PGAL is known as G3P.
AP Biology G3P Glyceraldehyde 3-Phosphate end product of Calvin Cycle energy rich 3 carbon sugar G3P is an important intermediate G3P glucose carbohydrates lipids phospholipids, fats, waxes amino acids proteins nucleic acids DNA, RNA
AP Biology RuBisCo Enzyme which fixes carbon from air (step 1 in Calvin Cycle) ribulose bisphosphate carboxylase the most important enzyme in the world! it makes life out of air! definitely the most abundant enzyme
AP Biology Accounting The accounting is complicated 6 turns of Calvin cycle = 2 G3P 6 CO 2 2 G3P (3C) 6 turns of Calvin cycle = 1 C 6 H 12 O 6 (6C) 6 CO 2 1 C 6 H 12 O 6 (6C) 18 ATP + 12 NADPH 1 C 6 H 12 O 6 any ATP left over from light reactions will be used elsewhere by the cell
AP Biology Characteristics of the Calvin Cycle 1. CO 2 enters through the stomates. 2. Hydrogen is released from its electron-carrier (NADPH) and is bound to CO 2 to make glucose. 3. Large amounts of energy (ATP) are needed for reactions to occur. 4. Each stage needs specific enzymes.
AP Biology Photosynthesis Summary Light reactions produced ATP produced NADPH consumed H 2 O produced O 2 as byproduct Calvin cycle consumed CO 2 produced G3P (sugar) regenerated ADP regenerated NADP NADPADP
AP Biology Light Reactions O2O2 H2OH2O Energy Building Reactions ATP produces ATP produces NADPH releases O 2 as a waste product sunlight H2OH2O ATP O2O2 light energy +++ NADPH
AP Biology Calvin Cycle sugars CO 2 Sugar Building Reactions ADP builds sugars uses ATP & NADPH recycles ADP & NADP back to make more ATP & NADPH ATP NADPH NADP CO 2 C 6 H 12 O 6 +++ NADPATP + NADPHADP
AP Biology Putting it all together CO 2 H2OH2OC 6 H 12 O 6 O2O2 light energy +++ Sugar Building Reactions Energy Building Reactions Plants make both: energy ATP & NADPH sugars sunlight O2O2 H2OH2O sugars CO 2 ADP ATP NADPH NADP
AP Biology
H2OH2O Energy cycle Photosynthesis Cellular Respiration sun glucose O2O2 CO 2 plants animals, plants ATP The Great Circle of Life,Mufasa! CO 2 H2OH2O C 6 H 12 O 6 O2O2 light energy +++ even though this equation is a bit of a lie … it makes a better story CO 2 H2OH2O C 6 H 12 O 6 O2O2 ATP energy +++
AP Biology Summary of photosynthesis Where did the CO 2 come from? Where did the CO 2 go? Where did the H 2 O come from? Where did the H 2 O go? Where did the energy come from? What’s the energy used for? What will the C 6 H 12 O 6 be used for? Where did the O 2 come from? Where will the O 2 go? What else is involved…not listed in this equation? 6CO 2 6H 2 OC 6 H 12 O 6 6O 2 light energy +++
AP Biology Supporting a biosphere On global scale, photosynthesis is the most important process for the continuation of life on Earth each year photosynthesis… captures 121 billion tons of CO 2 synthesizes 160 billion tons of carbohydrate heterotrophs are dependent on plants as food source for fuel & raw materials
AP Biology The poetic perspective… All the solid material of every plant was built by sunlight out of thin air All the solid material of every animal was built from plant material Then all the plants, cats, dogs, elephants & people … are really particles of air woven together by strands of sunlight! sun air