1.

Question : Describe the structure of chloroplast.

Answer»

Solution :Chloroplastsare themain siteof photosynthesis and bothenergyyieldingprocess (Light reaction ) and fixationof carbon dioxide (Dark reaction ) that takes place in chloroplast . ITIS a doublewall membrance bounded organelle, discoid or lens shaped, 4 -10`mu m` is diamter and`1 -33 mu m` is thickness. The membranceis a unit membranceand space beween themis 100 to`200 Å` Acolloidal and proteinaceous MATRIX called stroma is presentinside.
A sac likedmembranous systemcalledthylakoidor lamellase is present in stroma and theyare arrangedone abovethe otherforminga stack of coin like structure called grnum( plural grana). Eachchloroplast contans40 t0 80grana and eachgraanaconsistsof 5 to 30 thyaliods .
Thylakoidsfoundin granum are calledgrana lamellaeand in stroma are calledstromalamellae.Thylakoid disc sizeis 0.25 to 0.8 micro in diameter. A thinnre lamella calledFretmembranceconnects grana. PigmentsystemI islocated on outer thykoidmembrancefacingstromaandPigment systemI is locatedon innermembrancefacinglumenof thylakoid . Grana lamellaehave both PS I and PS II whereas stroma lamellae haveonly PSI . Chloroplast contains 30-35 % Proteins , 20-30%phospholipids , 5 - 10% chlorophyll , 4 - 5 % , Carotenoids ,70 Sribosomes , circular DNA and strachgrains. Inner surfaceof lamellar membracne consists of small sphericalstructurecalled as Quantasomes . Presence of70 S rbosome and DNA gives them status ofsemi-autonomy and proves endosymbiotic hypothesis whichsayschloroplastevolved from bacteria . Thylakoid contains pigment systems whichproduces ATP and NADPH ` + H^(+)`usingsolar ENERGY . Stroma containsenzymes whichreduces carbondioxideinto carbohydrates .


Discussion

No Comment Found

Related InterviewSolutions