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"Explore the intricate process of photosynthesis, where light energy, water, and carbon dioxide are converted into glucose and oxygen. Discover how plants utilize sunlight to create organic molecules and energy. Delve into the structure of plants, chloroplasts, pigments, and the mechanisms behind light reactions and the Calvin cycle. Unravel the connection between light-dependent and light-independent reactions, ATP production, and factors influencing photosynthesis. Witness the crucial role of photosynthesis in sustaining life on Earth and the interdependence of organisms in the biosphere."
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+ water + energy glucose + oxygen carbon dioxide glucose + oxygen carbon + water + energy C6H12O6 + 6O2 6CO2 + 6H2O + ATP dioxide light energy 6CO2 + 6H2O + + 6O2 C6H12O6 How are they connected? Heterotrophs and Autotrophs making energy & organic molecules from ingesting organic molecules exergonic Where’s the ATP? Autotrophs making energy & organic molecules from light energy endergonic
Plant structure • Obtaining raw materials • sunlight • leaves= solar collectors • CO2 • stomates= gas exchange • Found under leaves • H2O • uptake from roots • Nutrients • N, P, K, S, Mg, Fe… • uptake from roots
H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ Plant structure • Chloroplasts • double membrane • stroma • thylakoid sacs • grana stacks • Chlorophyll & ETC in thylakoid membrane • H+ gradient built up within thylakoid sac
Pigments of photosynthesis • chlorophyll & accessory pigments • “photosystem” • embedded in thylakoid membrane • structure function Why does this structure make sense?
Light: absorption spectra • Photosynthesis gets energy by absorbing wavelengths of light • chlorophyll a (dominant pigment) • absorbs best in red & bluewavelengths & least in green • other pigments with different structures absorb light of different wavelengths Why areplants green?
Photosynthesis • Light reactions • light-dependent reactions • energy production reactions • convert solar energy to chemical energy • ATP & NADPH • Calvin cycle • light-independent reactions • sugar production reactions • uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6 It’s the Dark Reactions!
Light reactions • Electron Transport Chain (like cell respiration!) • membrane-bound proteins in organelle • electron acceptor • NADPH • proton (H+) gradient across inner membrane • ATP synthase enzyme
Photosystems • 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 reactioncenter
ETC of Photosynthesis • ETC produces from light energy • ATP & NADPH • NADPH (stored energy)goes to Calvin cycle • PS II absorbs light • excited electron passes from chlorophyll to “primary electron acceptor” at the REACTION CENTER. • splits H2O (Photolysis!!) • O2released to atmosphere • ATP is produced for later use
Photosystem II Photosystem I ETC of Photosynthesis
Noncyclic Photophosphorylation • Light reactions elevate electrons in 2 steps (PS II & PS I) • PS IIgenerates energy as ATP • PS Igenerates reducing power as NADPH
Cyclic photophosphorylation • If PS Ican’t pass electron to NADP, it cycles back to PS II& makes more ATP, but noNADPH • coordinates light reactions to Calvin cycle • Calvin cycle uses more ATP than NADPH X
From Light reactions to Calvin cycle • Calvin cycle • Chloroplast stroma • Need products of light reactions to drive synthesis reactions • ATP • NADPH What is there left to do? Make sugar!
From CO2 C6H12O6 • CO2 has very little chemical energy • fully oxidized • C6H12O6contains a lot of chemical energy • reduced • endergonic • Reduction of CO2C6H12O6proceeds in many small uphill steps • each catalyzed byspecific enzyme • using energy stored in ATP & NADPH
1C 3C CO2 RuBP 5C 6C 3 ATP G3P to make glucose 3 ADP 3C PGA G3P 2x x2 3C 6 ATP 6 NADPH 2x 6 NADP 6 ADP Calvin cycle ribulose bisphosphate 1. Carbon fixation 3. Regeneration of RuBP Rubisco -enzyme that Binds CO2 to RuBP sucrose cellulose etc. 2. Reduction
Calvin cycle • PGAL important intermediate • Six turns of Calvin Cycle = 1 glucose PGAL glucose carbohydrates lipids amino acids nucleic acids
NADP ADP Summary • Light reactions • produced ATP • produced NADPH • consumed H2O • produced O2 as by product • Calvin cycle • consumed CO2 • produced PGAL • regenerated ADP • regenerated NADP
Factors that affect Photosynthesis • Enzymes are responsible for several photosynthetic processes, therefore, temperature and pH can affect the rate of photosynthesis. • The amount and type of light can affect the rate. • A shortage of any of the reactants,CO2 and/or H2O, can affect the rate.
Supporting a biosphere • On global scale, photosynthesis is the most important process for the continuation of life on Earth • each year photosynthesis synthesizes 160 billion tons of carbohydrate • heterotrophs are dependent on plants as food source for fuel & raw materials
sun CO2 H2O glucose O2 The Great Circleof Life! Where’s Mufasa? ATP Energy cycle Photosynthesis Cellular Respiration
light energy 6CO2 + 6H2O + + 6O2 C6H12O6 Summary of photosynthesis • 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 C6H12O6be used for? • Where did the O2 come from? • Where will the O2 go? • What else is involved that is not listed in this equation?
