CHLOROPLASTTHE HOUSE OF PLANTPHOTOSYNTHETIC MACHINERYPresented by-Mondalica ChalihaMSc Biotech
INTRODUCTION→ The term Chloroplast was first describedby Nehemiah Grew and AntonieVan Leeuwenhoek.→ “Chloro” means green while“ Plast” means living.→ Chlorophyll pigments presentin the chloroplast imparts thegreen colour to plants.→ Chloroplasts are present in plantsand other eukaryotic organisms that conducts photosynthesis.
STRUCTURE OF CHLOROPLAST→ They are planoconvexlens- like structuresabout 5µm diameterand 2 to 3 µm thick.→ The chloroplast comprise. A double layeredEnvelope. A granular stromaor matrix. A lamellar system. The Osmophilic globules called Plastoglobuli. Chloroplast DNA
THEENVELOPE→ It is composed of a system of double membranes ,eachof which is 50- 80 Å thick and has a unit membranestructure.→ The outer membrane is separated from the inner mem--brane by an intermembrane space of about 10nm.
STROMA→ The stroma fills most of the volumeof the Chloroplast.→ It contains about 50% of the proteinof Chloroplast.→ It contains Ribosomes and DNAmolecule.
THYLAKOIDS→ Consist of flattened and closed vesiclesarranged as membranous network→It may be stacked like a neat pile of coinsforming GRANA→There may be 40-80 grana in the matrixof a Chloroplast.→ Thylakoids includes light-absorbingpigment s, a complex chain of electroncarriers, and an ATP-synthesizing apparatus
PLASTOGLOBULI→ These are osmophilic bodies, lipid rich granulesin stroma
→Chloroplast DNA (cpDNA) - also known as plastidDNA (ptDNA).→ Circular double stranded DNA molecule.→ Chloroplast genome size 120-217kb .→ Majority of plants fall into 120-160kb. (Pelargoniumhas chloroplast genome size 217kb)CHLOROPLAST DNA
→ Contains about 100 genes to synthesize proteins→ cpDNA regions includes Large Single-Copy(LSC) & Small Single-Copy (SSC) regions, andInverted Repeats (IRA & IRB).→ Conifers and a group of legumes lack InvertedRepeats.
SOME CHLOROPLAST CODING GENESGene Location FunctionatpB Large single-copy region of chloroplast Beta subunit of ATP synthethase, whichfunctions in the synthesis of ATP viaproton translocationrbcL Large single-copy region of chloroplast Large subunit of ribulose 1,5-bisphosphatecarboxylase/ oxygenase (RUBISCO),which functions in the initial fixation ofcarbon dioxide in the dark reactions.matK Large single-copy region of chloroplast Maturase, which functions in splicing typeII introns from RNA transcriptsndhF Small single-copy region of chloroplast Subunit of chloroplast NADHdehydrogenase, which functions inconverting NADH to NAD + H+, drivingvarious reactions of respiration
FUNCTIONS OF CHLOROPLAST→ Chloroplast is the site for photosynthesisLight reaction → Thylakoid membranesDark reaction → Stroma.→Chloroplast is the site for photorespiration.
Suggested Readings :. Cell and molecular Biology – Gerald Karp. Cell Biology – S.C.Rastogi. Genetics- B.D.Singh. Lehninger Principles of Biochemistry – Michael M.CoxDavid L.Nelson