Essays /

Notes Essay

Essay preview

IB421 Final Take Home Exam. You may consult reference material but you are to work alone in answering these questions. Exams are due by 5 pm on Thursday, Dec 15th in IGB 1406 or e-mail pdf file to [email protected]

Short Answer: Please answer all 10 questions. Each is worth 5 points and your answers should not exceed 200 words. Please use 1.5 line spacing; calculations and drawings may be done by hand.
1. Describe the importance of genome reduction in plastid evolution.

Genome reduction is usually observed in endosymbiotic species when we have the association of eukaryotes and a cyanobacteria ( ancestor) is established. The inability of some endosymbiotic species to live outside of can sometimes explain the reasons why genome reduction occurs. In most of the cases, the cyanobacteria gets reduced and there is conservation of some of the genetic information via transfer of a large number of genes to the nuclear genome of the host. The lysis of bacteria occurs during division and enables the transfer of genes to the nucleus. 2. Why do C4 plants and CAM plants typically have higher water use efficiency than C3

plants? (Define water use efficiency in your answer.)
Water use efficiency is the inverse of the transpiration ratio ( water use efficiency =moles CO2 assimilated/moles H2O transpired). C4 plants and CAM plants unlike C3 plants both undergo little photorespiration. This is the reason why there is a spatial seperation between C3 and C4 photosyntetic pathway and thus C4 plants have a different leaf anatomy where mesophyll cells are close to the leaf surface and exposed to high levels of O2 which will prevent photorespiration and favor photosynthesis and thus water use efficiency by producing more moles of CO2 assimilated . CAM plants present a C3 and C4 seperate pathway in time and they have their stomata opening at night for CO2 uptake whereas their stomata close during the morning and this enables them to retain the water.

3. Describe the steps of starch synthesis in plants. What biochemical and signaling

mechanisms ensure that the rate of starch synthesis is balanced by the rate of photosynthesis and sucrose synthesis?
Starch synthesis starts in the plastids with the formation of ADP gluscose and the release of pyrophosphate. The formation of ADP glucose comes from the reaction of glucose -1-phosphate and ATP and catalyzed by AGPase (ADP-glucose phosphorylase) which is activated by 3phosphoglycerate and inhibited by phosphate (pi). Then starch synthesis ends with the addition of glucose elements at the end of a polymer chain with release of ADP. At the end of this process

starch branches are formed with SBEs, which will form 1, 6 linkages between glucose units. For regeneration of RUBP, the rates of starch synthesis, photosynthesis and sucrose synthesis must be balanced, there is then movement of triose phosphate into the cytosol at the expense of one phosphate (Pi) through the triose phosphate translocator (TPT) pathway which is placed in the chloroplast inner membrane. the mechanims are allosteric regulated: low rate of sucrose synthesis leads to a 3PG:Pi increase in chloroplasts and to high rate of starch synthesis (less TP left the chloroplast). Also high rate of sucrose synthesis leads to a decrease of 3PG:Pi ration in chloroplasts leading to low rates of starch synthesis (more triose phosphate left chloroplast).

4. Explain why activation of Rubisco is necessary and the mechanisms by which Rubisco

activation is achieved.
In order for carboxylation and oxygenation to occur during photorespiration under RUBISCO catalysis, Rubisco needs to be converted from its inactivate form into its active state as the active site of Rubisco will not distinguish those two substrate (CO2and O2). The activation of Rubisco requires the process of carbamylation of a lysine element, this will then result in providing a binding site for magnesium (mg2+). Then, once ribulose 1,5 phosphate is incorporated, Rubisco adopt a conformational change that will allow it to retain sugars (biphosphate) from the solvent. 5. The leaf photosynthesis model allows for scaling from the biophysical and biochemical

process of photosynthesis to determine net leaf level carbon fluxes. How is photorespiratory carbon release calculated in the model?

Photorespiratory carbon release can be calculated by by determining the increase in temp. [O2] that corresponds to photorespiration. Based on RUBP carboxylase and oxygenase properties we can determine the relationship to oxygen and carbon dioxide concentrations.it turns out the ratio of oxygenation to carboxylation is inversely proportional to carbon dioxide concentration and directly proportional to oxygen concentration. the equation then represents the ratio of oxygenation to carboxylation. O being the concentration of oxygen in percent and C the concentration of CO2 in parts per million. The factor x varies with temperature.

6. How and why does rising CO2 concentration affect the temperature optimum of C3

photosynthesis?
The rising of CO2 concentration stimulates C3 plants in the sense that the temperature rises for photosynthesis of C3 plants. The efficiency and outcome of photosynthesis would now depends on the initial temperature environment. For instance In warm regions at about 34 degree celsius, and elevated CO2 concentrations, the average growth is estimated to be 130% (B.A Kimball, 104). However, In extremely hot regions, CO2 elevation is most likely to have negative outcomes for plants, and this can lead to de decrease of reproductive success and a decrease in crop yield. Some growth chamber experiment has shown that the doubling of CO2 leads to the decrease of of stomatal conductance (37%) that will also lead to the elevation of leaf temperature (B.A Kimball, 104).

7. What is the relationship between the number of c subunits of CFo of the ATP syn...

Read more

Keywords

-1 /atp /o2 000 1 1.5 10 100 104 1050ppm 10micro 1100 130 14 1406 15th 180 1800 1p 2 2.3 2.where 200 2009 2010 2011 2015 2050 2100 22 250 280 2e 2x 3 30 300ppm 31 34 35 37 38 380pm 389 389ppm 39 3pg 3phosphoglycerate 4 4.6 40 5 5.3 50 550ppm 6 60 650 7 750 8 8.2 9 abl absorb absorpt acceptor acceptors.2 accessori acclim accomplish account accumul acerag achiev aco2/aco2 aco2/ao2 across actin activ activas actual ad adapt addit adopt adp adp-glucos affect agpas algorithm align alloster allow alon alreadi also alter although alway amaranthus amount anatomi ancestor anoth answer antenna anticip anyth apparatus arabidopsi arc arc5 arc6 architectur area around assembl assimil assimilated/moles associ atftsz1 atftsz2 atmospher atp averag avoid away b.a back bacteria balanc base basic benefici best better billion binari bind biochem biomass biophys biphosph bit blue blue-absorb bottom bound branch break bright brighter build c c3 c3plants c4 calcul call cam canopi capac captur carbamyl carbon carboxyl carboxylas case catalysi catalyt catalyz catch caus cell cellular celsius center centers.because centuri certain cfo chain chamber chang charg chemic chlophill chlorophyl chlorophyll chloroplast chromosom ci cinvers close co2 co2/o2 co2and code come common complet complex compon compos concanetr concencentr concentr concentrations.it concept condit condtion conduct confer confirm conform conserv consist constrict consult contain continu convers convert core correl correspond could counteract coupl cp43 cp47 creat crop cross curv cuticl cyanobacteria cycl cytosol [email protected] d1 damag dark day de death dec declin decreas defin definit degrad degre deopoxidas depend depress describ despit detail detect determin develop dictat differ dimer dioxid dioxyd dioxygen direct disappeac dissip distanc distinguish distribut diverg divis doesn done donor doubl draw drive drought dryness due dumb dynam dynamin e e-mail edulis/current effect effici electron element elev elimin elong emiss emit enabl encod end endosymbiot energi enhanc ensur environ enzym epoxidas equat especi essay essenti establish estim eukaryot event everi evid evolut evolutionari exam exampl exceed except excess excit exciton exclud exist expect expens experi explain explan expos extra extract extrem fact factor famili far fashion favor feed ferredoxin figure1 filament file final first fission fixatiion flash flow fluoresc flux fnr fo follow food foreign forest form format fossil found four ftsz ftz ftz1 ftz2 fuel full fulli function funnel furthermor fuse gain gas gate gene general generat genet genom get give global glucos gluscos go goe gradient grana greenhous grown growth h h20 h2o half hand happen harvest heat.light help high higher highest hight hint hit home homolog homologu host hot hour howev i.e ib421 igb import improv inabl inact inactiv incarbon includ incorpor increas individu induc industrialis influenc inform inhibit initi inner insid instanc instead intens interact interconnect invers invest involv keep kept kimbal kinas kinet knock known larg last lchii lead leaf least leav lectur left less level lh2 lhc lhcii light like limit line linkag lirrl littl live lobe local locat long longer loos loss lot low lower lumen lysi lysin magnesium mail main maintain maiz major make mani map massiv materi maximum may mean measur mechan mechanim membran membrane.before mesohpyl mesophyl method mg2 micro might million min mind mine mitrogen mode model moistur mole molecul morn move movement much multipl must mutat nadp narrow natur near necessari need negat net next night nitrogen non non-photochem nonphotochem nonphotosynthet note npq nuclear nucleus number o o2 observ obtain occur old one open opportun opposit optim optimum orang order origin other outcom outsid overact overal overlap overreduc oxid oxidas oxyd oxygen oxygenas oxyperoxid ozon p680 pair par part partial passag pathway pdf peak peopl per percent perform period peripher perspect pgci ph phoosynthesi phosphat phosphoryl phosphorylas photochem photodamag photoinhibit photon photoprotect photorespir photorespiratori photosyntet photosynth photosynthesi photosynthet photosystem phtosynthesi phycobilisom physic pi pictur pigment place plant plastid plastohydroquinon plastoquinon plastoquinonex2 play pleas pm pn point polluant polym popul possibl ppfd ppm presenc present prevent previous primari primer probabl problem process produc product progress prokaryot properti proport protect protein proton provid ps1 ps2 purpos put pyrophosph qa qb qe qi quench question quinon qz radiat rais rang rangea rapid rare rate rates.the ratio ration reach reaction reactiv rearrang reason receiv recent recoveri red reduc reduct reemiss refer reflect regener region regul regulated/dynamic relat relationship relax relay releas reoxid repair replac repres reproduct requir rereduc respect respons result retain return reveal revers ribulos rice rich ring rise role rotat rubisco rubp run satur sbes scale season second section see seen select sens sensit separ seper sever shape share shell shift short show shown side signal signific similar simul simultan sinc site size slower slowest small smaller soil solar solvent sometim somewhat space spatial speci special specif spectra spectrum speed stack starch start state step still stimul stoke stomat stomata stress stroma stromal strong stronger structur substrat subunit success sucros sugar suggest sunflow sunlight suppli support surfac surviv symmetr synthas synthes synthesi system take temp temperatur ten though three throughout througout thursday thus thylakoid till time timescal top total toward tp tpt transduct transfer transform transit transloc transpir transport trend tri trios true tubulin turgor turn twice two type typic under undergo unit unknown.a unlik uptak use usual util valid valu vapor vari via warm water wavelength way well wh wherea wide wire within without word work worth would x year yield zeaxanthin zyloxanthin