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bio 202 #5
| Question | Answer |
|---|---|
| inorganic carbon in photosynthesis | carbon dioxide |
| organic carbon in photosynthesis | (CH2O) in the products |
| is photosynthesis exergonic or endergonic | endergonic |
| light reactions inputs | light, water, NADP+, ADP |
| light reactions outputs | O2, NADPH, ATP |
| location in chloroplast where light reactions occur | thylakoid |
| carbon reactions inputs | CO2, NADPH, ATP |
| carbon reactions outputs | (CH2O)n---> sugar, NADP+, ADP |
| location in chloroplast where carbon reactions occur | stroma |
| photosynthesis reactions | CO2 + H2O + light energy ---> (CH2O)n + O2 |
| true or false: the primary purpose of photosynthesis is to produce oxygen | false |
| true or false: the shorter the wavelength of light, the more energy it contains | true |
| is cellular respiration anabolic or catabolic | catabolic |
| is cellular respiration endergonic or exergonic | exergonic |
| is carbon getting oxidized or reduced in cellular respiration | oxidized |
| major purpose of cellular respiration | make ATP |
| is photosynthesis anabolic or catabolic | anabolic |
| is carbon getting oxidized or reduced in photosynthesis | reduced |
| major purpose of photosynthesis | make sugars |
| how are the reactions of cellular respiration and photosynthesis related to each other | they are the inverse of each other |
| true or false: plants have chloroplast and can therefore live without mitochondria | false--> energy produced during light reactions of chloroplasts is used to make sugars, not drive endergonic reactions of cell -plant cells still need mitochondria so that there's way to make ATP that can be used to power any endergonic rxn cell needs |
| plants have.. | chloroplasts, mitochondria, perform cellular respiration, and perform photosynthesis |
| how are chloroplasts and mitochondria similar in structure | both have outer and inner membranes, outer membrane is porous and allows free diffusion of some hydrophilic molecules, both have DNA and ribosomes |
| how are chloroplasts and mitochondria different in structure | chloroplast has thylakoid, a 3rd membrane-bound structure that mitochondria don't have -chloroplasts are larger than mitochondria |
| significance of O2 output in light reactions | none for photosynthesis, provides electron acceptor for respiration |
| significance of ATP output in light reactions | used as an energy source to power the carbon cycle reactions |
| significance of NADPH output in light reactions | used as an energy source to power the carbon cycle reactions |
| significance of sugar (carbs) output in carbon reactions | storage of energy, foundation for macromolecule building |
| significance of ADP output in carbon reactions | gets recycled for use in light reactions |
| significance of NADP+ output in carbon reactions | gets recycled for use in light reactions |
| where did this mass come from in plant that gained 1000grams in weight | from fixing inorganic CO2 into sugars/starches (organic molecules) |
| relationship between wavelength of light and amount of energy it contains | the shorter the wavelength, the more energy is contains -inversely related |
| true or false: photons are made up of quantums | true--> they are made of many quantums |
| quantum | an indivisible packet of energy |
| why do the leaves of most plants appear green | green light is the least absorbed wavelength by the chlorophyll pigments |
| which pigments are responsible for the bulk of photosynthesis | Chl a and Chl b |
| what happens to the pigments within a chloroplast when they absorb light energy | photon of light excites electron in chlorophyll molecule, causing it to reach a state of high potential energy (i.e., an excited state) -->unstable electron & falls back to ground state - releases energy in the form of heat and fluorescence as falls |
| how are chloroplasts and mitochondria similar in function | both use ETC to create a H+ gradient and synthesize ATP |
| how are chloroplasts and mitochondria different in function | chloroplast uses ATP right away to power synthesis of sugars during carbon reactions, something the mitochondria doesn't do |
| photosystem | Made up of a reaction center and light harvesting complex (LHC). It’s an assembly of chlorophyll molecules, accessory pigments, and proteins embedded in the thylakoid membrane. Used for capturing light energy and transferring it to electrons. |
| light harvesting complex | Part of a photosystem that contains a collection of light-absorbing pigments linked together through a protein complex. It absorbs photons and funnels the energy to nearby reaction center in the photosystem. |
| reaction center | It is a part of a photosystem that contains a “special pair” of chlorophyll molecules. This special pair is part of a protein complex that transfers electrons from the special pair to a primary electron acceptor. |
| what term refer to the photosynthetic reactions that produce ATP and NADPH | light-dependent reactions |
| what is the first step of photosynthesis | excitation of chlorophyll molecules |
| what happens to the electrons in all chlorophyll molecules of PS11 and PS1 when light is absorbed | the electron moves to an outer, unstable shell |
| the ultimate source of electrons for the electron transport chain in the light-dependent reactions | H2O |
| what does not occur during Cyclic Electron Flow | -energy travels through PS11 -NADP+ is reduced to NADPH |
| resonance energy transfer | - light harvesting complexes of photosystems -chlorophyll absorbs light--> excite electrons -releases energy & becomes stable electron--> release photon -keeps exciting adjacent electrons -keeps going until excite special pair in rxn center |
| true or false: when any chlorophyll pigments get excited, it gives away an electron | false |
| P680 and P700 are examples of | chlorophyll |
| how are electrons replaced when the special pairs loses its electrons to the primary acceptor | PS11- replaced by oxidation of water PS1- replaced by electrons moving down the ETC from the PS11 |
| why is P680+ able to oxidize water so readily | P680+ is unstable and becomes a strong oxidizing agent in oxidized form -allows the oxidation of water into oxygen and the reduction of P680+ to P680 |
| at what points in the pathway are protons pumped | only pumped through the cytochrome complex |
| direction of proton pumping and what membrane do they cross | -actively transported across the thylakoid membrane -come from the stroma of the chloroplasts to the thylakoid lumen |
| what other contributing factor adds to the proton gradient | contributing factor: when water is oxidized by P680+ -p680+ takes the electrons -molecular oxygen is formed -H+ ions are left behind in the thylakoid lumen --> adds to acidity there |
| path that an electron takes during linear electron flow | -electrons start as part p680 in PS11--> transferred to primary e- acceptor--> e- pass to PQ to Cytochrome complex to PC--> to P700+--> add light to excite e- --> primary e- acceptor in PS1 accepts e- & to Fd --> NADP reductase --> NADP+ to make NADPH |
| complexes/proteins involved cyclic electron flow pathway | PSI, Fd, Cytochrome complex, and PC |
| what is made during CEF and how is this possible | -ATP is made because movement of electrons through cytochrome complex allows more proton pumping and contributes to the gradient needed for ATP synthesis to happen |
| inputs for carbon reactions | ATP, CO2, NADPH |
| in carbon reactions, the enzyme that catalyzes the capture of carbon dioxide and the formation of 3-phosphoglycerate is | RuBisCo |
| cofactor that is the electron donor for carbon fixation | NADPH |
| why do carbon-fixation reactions require ATP | to provide energy for endergonic reactions |
| what is not a stage of carbon reactions | photorespiration |
| what are two substrates of RuBisCo | oxygen and carbon dioxide |
| one advantage of photorespiration allows plants to release absorbed light energy in the absence of what substance | carbon dioxide |
| photorespiration results in fixation of | oxygen onto an organic backbone |
| 3 phases of carbon reactions | carbon fixation, reduction, and regeneration |
| carbon fixation | carbon from inorganic carbon dioxide is attached to an organic backbone (RuBP) |
| reduction | the end carbon goes from bonding to an O to an H, and gains electrons -product has more energy than substrate -endergonic reaction that uses ATP and NADPH |
| regeneration | RuBP (ribulose) is regenerated -substrate for RuBisCo |
| how much ATP and NADPH is needed for one turn of the carbon reaction | 3 ATP, 2 NADPH |
| how much ATP and NADPH is needed to get 2 G3P | 18 ATP and 12 NADPH -lots of energy` |
| what happens to the G3P's that are made during the calvin cycle | -used directly as an energy source --> G3P is one the intermediates of glycolysis -serve as backbone for other organic molecules (lipids, amino acids) -used to make glucose which can be stored in the form of starch (polymer of glucose) |
| catalytic function of RuBisCo in photosynthesis | fix inorganic carbon to an organic backbone |
| catalytic function of RuBisCo in photorespiration | fix inorganic oxygen to an organic backbone |
| what conditions affect the rate of RuBisCo catalysis of photorespiration | increase of photorespiration is caused by higher temps--> CO2 is less soluble, so it's harder to distinguish between CO2 and O2 |
| how are O2 and RuBisCo related | oxygen is a competitive inhibitor of RuBisCo |
| competitive inhibitor | small molecule that binds to the active site of an enzyme and effectively blocks the binding of the enzyme's normal substrate |
| negatives of photorespiration | -reduces the amount of inorganic carbon that gets fixed into useful intermediates of the calvin cycle -costs ATP to turn that 'lost' carbon back into something useful |
| benefits of photorespiration | uses up excess light energy so the plant isn't damaged |
| stomata opening causes | gas exchange, transpiration, and carbon reactions |
| guard cells | cells that flank the stomata -responsible for determining whether stomata are open or closed -usually found on the underside of leaves as part of the way epidermal layer |
| what causes stomata to open | they swell with water --> tension changes the shape of the guard cells--> pulls the guard cells apart -->causes space in between them to open up |
| turgid | swelling with water -gain water and swollen/puffed out -day time |
| flaccid | not swollen with water -wrinkled and not rigid -nighttime |
| what causes stomata to close | they are not swollen with water--> lac k of tension in cells causes them to flatten out against each other--> eliminates the space between them --> stomata clsoes |
| what happens during a signal transduction pathway | signaling molecule outside cell activates receptor (often a transmembrane protein)--> activated receptor stimulates a series of protein phosphorylation/ dephosphorylation events in a cell & reaches target protein --> cellular response |
| common signaling molecules | first messenger, ligand, or stimulus |
| common cellular responses | cell division, cell movement, cell differentiation, transport of something in/out of the cell, changes in gene expression, stomata opening |
| stomata opening--> in what cells does this signal transduction pathway occur | guard cells |
| stomata opening--> what is the first messenger in the pathway | blue light |
| first messenger | molecule that initiates a signal transduction cascade -can also be referred to as a stimulus (light or sound) or as a ligand (small molecule) |
| stomata opening--> what is the receptor | -receptor is phototropin -purpose is to relay the signal it received from outside the cell, to inside the cell |
| stomata opening--> basic gist of the relay system that causes the cellular response? | Phot1 phosphorylates a protein--> activates phosphatase--> activates another kinase to activate H+ pump -Phot receives the signal, a series of proteins become phosphorylated or dephosphorylated to become activated and thereby activate another protein |
| stomata opening--> what is the final cellular response | water enters the vacuole which causes the guard cells to swell and allows the stomata to be opened |
| guard cell--> what type of transport is used to move H+ ions across the guard cell membrane | primary active transport -requires energy |
| guard cell--> what type of transport is used to move K+ ions across the guard cell membrane | -facilitated diffusion -doesn't require energy |
| process that causes water to move into the cell | osmosis |
| osmosis | diffusion of water from regions of low solute concentration to high solute concentration -does not require energy |
| where in the cell does the water specifically go | vacuole |
| general mechanism of stomatal opening | -blue light activates Phot -signal transmitted from Phot to proteins -activates H+ pump--> exit H+ -K+ diffuses in cell to equalize charge gradient (H+ exit) -water enters (equalize solute gradient from K+) -vacuole swells & stomata opens |
| function of output domain of phototropin | kinase domain -photosensory region is stimulated by blue light and causes the output domain to phosphorylates itself and activates protein -protein phosphorylates target protein once activated |
| what is the function of the LOV domain | -to receive blue light stimulus and start signal transduction pathway -blue light causes coenzyme part of LOV domain to become bonded to amino acid in LOV domain.--> allows kinase domain to loosen away from rest of protein so kinase domain can function |
| autophosphorylation | when a protein phosphorylates itself |
| what might happen if there was a mutation in phototropin such that phosphorylation was prevented at some spots | plots wouldn't be able to become activated thereby not allowing it to activate proteins downstream in the pathway -would prevent guard cell swelling and stomata opening |
| what might happen if there was a mutation in the LOV domain of phototropin such that it absorbed purple light in addition to blue light | activity of Phot would be increased because it could be stimulated/activated by more light wavelengths -guard cells would be full of water more often causing stomata to be open more--> more water loss than preferred |
| what might happen if there was a mutation in the output domain of phototropin so it no longer recognized its substrate | Phot wouldn't be able to autophosphorylates and it wouldn't be able to transit the signal -guard cells would remain flaccid and stomata would stay closed |
| "photo" part | light reactions -use light to power these reactions |
| "synthesis" part | carbon reactions |
| excitation of chlorophyll by light | -when pigment absorbs light, goes from a ground state to excited state (unstable) -when excited electrons fall back to the ground state, photons are given off (after glow called fluorescence) |
| photosystem | consists of reaction-center complex surrounded by light-harvesting complexes |
| reaction-center complex | type of protein complex |
| light-harvesting complexes | pigment molecules bound to proteins that transfer the energy of photons to the reaction center |
| primary electron acceptor | in the reaction center accepts excited electrons and is reduced as a result |
| photosystem 2 | functions first -absorbing wavelength 680nm -the reaction-center chlorophyll a of PS II is called P680 |
| P680 | reaction-center chlorophyll a of PSII |
| photosystem 1 | functions second -absorbing wavelength 700nm -the reaction-center chlorophyll a of PS I called P700 |
| P700 | the reaction-center chlorophyll a of PS I |
| how does P680 in PSII replace the electron it transfers | P680+ (the oxidized form of P680 that has lost its electrons to the primary electron acceptor) is a strong oxidizing agent, and it can oxidize water. Water loses its electrons (becomes oxygen) and donates them to P680+, regenerating P680. |
| routes for electron flow | -linear electron flow -cyclic electron flow |
| linear electron flow | the primary pathway -involves both photosystems and uses light energy to produce ATP and NADPH |
| cyclic electron flow | -uses photosystem I -produces ATP but not NADPH -also depends on light energy in order to function -no oxygen released -generates surplus ATP satisfying higher demand in calvin cycle |
| linear electron flow movement | -Electron transported from PS II to PS I via 3 proteins -Oxygen released as water is oxidized -Energy lost by electron during its transit used to set up H+ gradient -H+ gradient powers ATP synthesis by chloroplast’s ATP synthase |
| 3 proteins electrons flow through | -PQ, cytochrome, PC |
| ATP/NADPH needed for carbon reactions | -fixation of one CO2 molecule uses 3 ATP & 2 NADPH molecules -1.5:1 ratio -ratio of linear electron flow 1.28 (not enough ATP made) -additional H+ need to be pumped across the thylakoid membrane to accommodate the ATP requirements of carbon rxns |
| why do we use the Calvin cycle? | calvin cycle uses more ATP than NADPH so this is a way to ease ATP at the expense of NADPH |
| optimal operation of carbon reactions requires | both linear and cyclic electron flow |
| photosynthesis | process that converts solar energy into chemical energy |
| how does photosynthesis nourish entire living world | -responsible for O2 we breathe -the food we eat -fuel we burn (wood, fossil) |
| photosynthesis reaction | 6 CO2 + 6H2O + light energy -----> C6H12O6 + 6O2 |
| chloroplast | -sites of photosynthesis in plants -structural organization allows for chemical rxns of photosynthesis |
| where is chlorophyll located | in the membranes of thylakoids |
| stroma | dense interior fluid -in chloroplast |
| granum | stacks of thylakoids |
| energy transduction reactions are localized in thylakoid membranes and includes | -capture of light energy -production of ATP -production of NADPH -splitting of water |
| stage 1 of photosynthesis | -light reactions -very similar to oxidative phosphorylation in mitochondrial inner membrane—main difference is where the e- wind up -transferred to NADPH rather than O2 -Water becomes oxidized to form oxygen |
| stage 2 of photosynthesis | -The ATP & NADPH produced in stage 1 used to make sugars from CO2 -rxns called the carbon fixation rxns -start with CO2 -end with glyceraldehyde-3-phosphate -exported to cytosol used to make sucrose & other organic molecules |
| wavelength | the distance between crests of waves -determines type of electromagnetic energy |
| energy relationship to wavelength | -energy is inversely proportional to wavelength -shorter wavelength the higher energy content |
| pigments absorb | visible light |
| true or false: all pigments absorb the same wavelengths | false -different pigments absorb different wavelengths |
| what happens to wavelengths that are not absorbed | they are reflected or transmitted |
| why do leaves appear green | because chlorophyll reflects and transmits green light |
| chlorophyll a | green molecule -main photosynthetic pigment |
| chlorophyll b | green molecule -accessory pigments |
| carotenoids | absorb red or orange in color |
| amount of pigments in plants | -depending on the plant, there are other pigments in small quantities that absorb light |
| absorption spectrum | graph plotting a pigment's light absorption versus wavelength |
| activity spectrum | the relative effectiveness of different wavelengths of radiation in driving a process |
| light reactions absorb light and transfer electrons | -light absorbed by pigments w/in thylakoid membrane of chloroplast -e- reach excited state--> move through ETC -H+ pumped against gradient b/c of e- movement -ATP synthase uses energy stored in H+ gradient to make ATP |
| mitochondria H+ movement | H+ pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix |
| chloroplast H+ movement | H+ are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma |
| most abundant enzyme on earth | RuBisCo |
| carbon reaction inputs/outputs | for every 6 CO2 that enter carbon rxns, 12 G3P are made -2 out of 12 G3P exit the cycle and can be used as an energy source or as a backbone for other organic molecules |
| sugars can be | stored or consumed |
| control of stomata | -light activates receptor protein (series of proteins become activated through a relay) -proton pumps push H+ out of cell -uptake of K+ ions by guard cells -loss of K+ ions by guard cells |
| review of signal transduction | -primary messenger is ligand -secondary messenger is a small molecule that propagates the signal from outside of the cell to an effector inducing cellular response -cellular response -binding of ligands to receptors is specifc |
| guard cells regulate transpiration and gas exchange | -majority of water loss is through stomata -each stoma is flanked by pair of guard cells -GC control stoma diameter by changing shape -GC help balance water conservation with gas exchange for photosynthesis |
| leaf tissue | broad surface areas and high surface-to-volume ratios -increase photosynthesis and increase water loss through stomata |
| point of having stomata open | gas exchange and transpiration |
| signal transduction in guard cells | -water and CO2 are necessary components of photosynthesis -CO2 enters stomata flanked by guard cells -water enters at the roots and is pulled upward as a result of transpiration combined with cohesion |
| photorespiration | -reduces the amount of inorganic carbon that gets fixed as organic carbon during calvin cycle -carbon loss can be partially overcome but at expense of ATP -addition of O2 to organic backbone rather than CO2 |
| positive of photorespiration | when there is an excess of light, it protects the plant and allows it to get rid of the excess energy absorbed |
| excess light and heat creates | low CO2 solubility |
| oxygen is | competitive inhibitor of CO2 |
| under high temps, photorespiration | increases because CO2 is less soluble and Rubisco's active site is less able to distinguish between CO2 and O2 |
Created by:
17mahomol