Term
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Definition
• reverse of cellular respiration
• endergonic suite of reactions that reduces CO2 to glucose
• 6CO2 + 12 H20 + light -> C6H12O6 + 6O2 + 6H2O
• consists of two independent sets of reactions
• occurs in chloroplasts |
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Term
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Definition
• split water and make ATP and NADPH
• input: light, ADP, NADP+, water
• output: oxygen, NADPH, ATP
• light energy used to oxidize water to O2 - electrons derived from this are used to reduce NADP+ to NADPH and reduce CO2 to carbohydrate (calvin cycle)
• include Photosystems II and I and Z Scheme |
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Term
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Definition
electrons used to reduced NADP+
• electron in a chlorophyll P680 molecule is excited
• pheophytin takes electron from chlorophyll
• electron passed onto ETC - ETC contains quinones and cytochromes as electron carriers
• pumps proteins into interior of thylakoid, creating a proton gradient (proton-motive force)
• ATP synthase uses proton-motive force to synthesize ATP (process called photophosphorylation)
• original chlorophyll molecule oxidized after its excited electron was taken away and then water is split
• found in thylakoid membrane facing inside of grana |
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Term
| antenna center of Photosystem II |
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Definition
• so electronegative that water is oxidized and electrons are used to reduce chlorophyll back to its original state
• oxygen release
• highly endergonic - only possible b/c energy in sunlight drives it by removing electrons from PSII
• only time water is ever split |
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Term
| summary of Photosystem II |
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Definition
| starts with an electron being promoted to a high-energy state and ends with production of ATP via chemiosmosis |
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Definition
• excited electron passed to iron- and sulfur-containing proteins, then ferredoxin
• enzyme called ferredoxin/NADP+ oxidoreductase transfers two electrons and a proton to NADP+ to form NADPH
• found in thylakoid membrane facing stroma |
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Term
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Definition
PSI and PSII work together to maximize photosynthetic efficiency
• at end of Photosystem II, plastocyanin (a protein) accepts electron from PSII ETC and transfers it to a chlorophyll molecule in PSI
• helps replace electrons lost during PSI (since PSI doesn’t split water like PSII)
• plastocyanin increase rate at which PSI reactions can occur, facilitating more rapid NADPH production
• some G3P drawn off to make glucose, rest recycled to regenerate RuBP |
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Term
| still don’t understand why there is so much physical separation between PSII and PSI since ________ |
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Definition
| functions so tightly integrated |
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Term
| light-independent reactions (Calvin cycle) |
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Definition
• use ATP and NADPH to reduce CO2 and make sugars
• input: ATP, CO2, NADPH
• output: ADP, NADP+, G3P
• oxidizes the light-reactions product NADPH to NADP+
• occurs in the stroma
• electrons derived from this oxidation reaction are used to reduce CO2 to G3P |
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Term
| overview of light-independent reactions (Calvin cycle) |
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Definition
• carbon fixation: C is fixed when CO2 combines with a 5-carbon compound called RuBP for form a 6-carbon molecule that is split to form two 3-phosphoglycerate molecules (fixation phase)
• these 3PG molecules are phosphorylated by ATP and then reduced by NADPH to make glyceraldehyde 3-phosphate (G3P) (reduction phase)
• then rest of G3P are used to keep the cycle going (regeneration phase) |
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Term
| CO2 gets into plant to rubisco through _______ |
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Definition
| spaces in leaf called stomata |
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Term
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Definition
• guard cells around pores
• also allows water out - under prolonged hot, dry conditions plants close their stomata
• result - CO2 can't get in, O2 can't get out. eventually the ratio of O2 to CO2 increases to the point that the plant will shift from photosynthesis to photorespiration
• if CO2 concentrations low, protein pumps establish charge gradient across membrane, causing cells to swell and create a pore |
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Term
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Definition
| • CO2 stored in one cell and used in another |
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Term
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Definition
| • CO2 stored at night and used during the day |
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Definition
• most abundant pigment in thylakoid membranes
• chlorophyll a and b absorb red and blue wavelengths and transmit green (makes red and blue most effective at driving photosynthesis) |
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Term
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Definition
• common accessory pigments that absorb blue and green, transmit yellow, orange or red
• pass energy on to chlorophyll
• extends range of wavelengths that can drive photosynthesis
• two classes: carotenes and xanthophylls
• serve a protective function - quench free radicals - without carotenoids, chlorophyll molecules are destroyed |
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Term
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Definition
production of more ATP instead of making NADPH
• occurs in green algae and plants
• PSI transfers electrons back to the ETC in PSII to augment ATP generation through photophosphorylation |
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Term
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Definition
| • equally common in both types of membrane |
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Term
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Definition
| • ATP produced by ATP synthase (just like in cellular respriation) as protons fall back from thylakoid lumen into stroma |
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Definition
• enzyme that catalyzes the fixation of CO2 (attaches CO2 to RuBP)
• has 8 active sites where CO2 is fixed
• catalyzes competing reactions with very different outcomes b/c it can also bind to O2 under certain conditions
• with CO2 during photosynthesis: makes two moles of product used in Calvin cycle (3PG)
• with O2 during photorespiration: makes one mole of product used in Calvin cycle (RuBP) and a product that when processed, CO2 is released and ATP is used |
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Term
| Visible light ranges in wavelength from ________ nm; light with shorter wavelength has more energy than that of longer wavelength. |
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Definition
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Term
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Definition
| molecules that can absorb the electromagnetic energy of light |
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Term
| when a photon of light hits a pigment, the photon can be ___________ |
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Definition
| absorbed, transmitted or reflected |
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Term
| what happens when a photon is absorbed by chlorophyll |
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Definition
• chlorophyll has long lipid tail that anchors it in the thylakoid membrane and a head with a large ring structure with a magnesium atom in the middle where light is absorbed
• when photon hits chlorophyll, energy is transferred to an electron in the head region
• energy causes electron to move to a higher orbital
• when electron falls back down, excess energy is released
• some of that energy transferred to another chlorophyll molecule in antenna complex
• excited electron passed from reaction center to electron acceptor (this redox reaction is point at which electromagnetic energy is converted to chemical energy) |
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Term
| a photosystem consists of |
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Definition
| antenna complex and reaction center |
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Term
| antenna complex transmits the energy to _____________ |
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Definition
| special chlorophyll molecule called the reaction center |
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Term
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Definition
• carbon fixation: carbon fixed when CO2 combines with RuBP (5 carbon compound) to form a 6-carbon molecule that is split to form two 3-carbon molecules
• 3PG molecules phosphorylated by ATP and then reduced by NADPH to make G3P
• some G3P drawn off to make glucose and rest of the G3P is recycled to regenerate RuBP |
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Definition
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Definition
• when an excited electron falls back down
• energy released as heat and electronmagnetic radiation
• about 2% of photons |
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Definition
• light strikes, electron excited
• energy passed to nearby chlorophyll molecule, where another electron is excited: resonance
• once energy transmitted, original excited electron falls back to its ground state |
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Term
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Definition
• excited electrons transferred to a molecule that acts as an electron acceptor
• electromagnetic energy transformed to chemical energy
o cannot be reemitted as fluorescence
• when light excites electrons, reactions become exergonic – otherwise are endergonic |
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Definition
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Definition
| fluid-filled space between thylakoids and inner membrane |
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Definition
| photosynthetic organisms, make all of their own foods form ions and simple molecules |
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Definition
| non-photosynthetic organisms, have to obtain their food from other organisms |
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Definition
rate of photosynthesis increases dramatically when far-red and red light waves used together instead of separately
• because photosystems much more efficient when operating together |
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Term
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Definition
| light energy capture by chlorophyll and transformed to chemical energy stored in ATP |
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Term
| organisms that use _________ as an electron acceptor in cellular respiration can produce much more ATP than organisms that use other electron acceptors |
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Definition
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Term
| G3P molecules make ________ |
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Definition
• glucose and fructose
• can be combined to make sucrose or starch
• starch produced in chloroplast; sucrose produced in cytosol
• when photosynthesis slow, mainly sucrose made
• when photosynthesis fast, starch made
• starch acts as temporary sugar-storage product
• not water-soluble, so can't be transported to other parts of plant
• at night, starch broken down and used to make sucrose |
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