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14 Cards in this Set
- Front
- Back
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overall equation
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6C02 + 6H2O + light ----> C6H12O6 + 6O2
CO2 enters and leaves through stomata water is provided from soil O2 liberated comes from H2O |
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Light Reactions
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light energy and water used in first pathway (photophosphorylation) to produce ATP
NADPH + H+ and O2 NADPH used in biosynthetic reactions (contains a lot of energy in its reduced form) |
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Calvin Benson Cycle (Dark Reactions)
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CO2 and ATP plus NADPH and H+ produced in photophosphorylation are used in the Calvin-Benson cycle to produce sugars
1) carbon fixation (RuBP and CO2 combine via enzyme rubisco) (forms 2 molecules of 3-phosphoglyceric acid-catalyzed by RuBP corboyslase (rubisco) 2) reduction of sugar production (3 GP allocated to produce sugar) 3) regeneration of RuBP needs to run 6x in order to produce one sugar molecule used in light dependent reactions takes place in the stroma requires ATP and NADPH and H+ (noncyclic photophosphorylation products) |
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Energy of a Photon
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E= h times v
h is plank's constant v is frequency v =(C)/wavelenth C= velocity times the speed of light |
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Properties of Light
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-form of electromagnetic radiation
-exists as photons which exhibit wavelike properties -energy content of photon is inversely proportional to the wavelength of the light |
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3 things that happen when light strikes an object
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reflects
transmission (light passes through) absorption of a photon, goes into an excited state, electron can return to ground state and emit light of a lower wavelength (less energy). this is fluorescence (occurs in mitotic spindle) |
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Photosynthetic Pigments
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atom can only absorb photons corresponding to the atom's available electron energy levels =absorption spectrum
cholorophylls a and p- predominant in green plants, ring containing Mg 2+, hydrocarbon tail cholorphylls absorb blue and red wavelengths accessory pigments- absorb photons in the region between blue and red carotenoid |
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Process of Absorption- chlorophyll strucuture
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photon strikes chlorophyll
electron is in excited state shuttle along by electron carriers makes ATP by chemiosmosis photon striking antenna structure- energy is shuttled by RESONANCE TRANSFER energy which goes to the reaction center chlorophyll has magnesium ion in the middle and a porphyrin ring which is light harvesting long non-polar fatty acid chain |
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Photophosphorylation
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excited chlorophyll (Chl) is a reducing agent (will give up electrons), reacts with oxidizing agent
excited electron is shuttled along a series of electron-carrier molecules in the photosynthetic membrane in proton-pumping channel, proton translocation occurs resulting in ATP synthesis by chemiosmosis Photosystem 1: reaction center contains Chl a -700 nm wavelength absorption Photosystem 2: reaction center contain a chl a -608 nm wavelength absorption -requires more energetic photons that 1 |
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Noncyclic Photophosphorylation
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uses photosystems 1 and 2 together with ATP
electrons from H2O replenish chl molecules which gave up electrons O2 is by-product of the breakdown of H2O excited electron from photosystem 2 goes to electron transport chain and water is split which allow excited electron to be replaced. electron then goes to excite photosystem 1, and protein Feridoxin (electron acceptor) goes to NADP+ reductase to make NADPH + H+. PS 2: H20 goes to O2 to make ATP PS1: produces NADPH and H+ |
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Cyclic Photophosphorylation
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forms ATP but not NADPH
end of redox chain, electrons are returned to electron deficient chl's, no O2 is produced produces additional ATP for reactions of the Calvin Benson Cycle photon --->excited elctron--->electron transport chain--->adp +Pi goes to ATP uses photosystem 1 |
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Chloroplasts form ATP by Chemiosmosis
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electrons move through a series of redox reactions releasing energy
energy allows protons to be pumped across thylakoid membrane from the stroma establishes a pH gradient (proton motive force) ATP synthase couples diffusion of protons back to the stroma with ATP synthesis |
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Photorespiration
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important in enzymes
rubisco catalyzes reaction with O2 and CO2 requires light and uses oxygen reduces efficiency of photosythesis RuBP and O2 forms glycolate (2C) which enters peroxisomes, is oxidized and the product enters mitochondria and is broken down releasing CO2 oxygenase function of rubisco is favored at higher temperatures and low CO2 levels |
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Interrelations
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3PG of Calvin Benson can be converted to pyruvate
G3P from Calvin Benson can be converted to hexose phosphates which can enter glycolysis |
