CELL ORGANELLECELL ORGANELLE

PRESENTED BYPRESENTED BY►DARSHANA - 3DARSHANA - 3►MADHURA B - 5 MADHURA B - 5

INTRODUCTIONINTRODUCTION► In cell biology, an organelle is a specialized In cell biology, an organelle is a specialized

subunit within a cell that has a specific subunit within a cell that has a specific function and is usually separately enclosed function and is usually separately enclosed within its own lipid bilayerwithin its own lipid bilayer

► Organelles are identified by microscopy and Organelles are identified by microscopy and can also be purified by cell fractionationcan also be purified by cell fractionation

► There are many types of organelle There are many types of organelle particularly in eukaryotic cell. Prokaryotes particularly in eukaryotic cell. Prokaryotes were once thought not to have organelles, were once thought not to have organelles, but some egs have now been identifiedbut some egs have now been identified

HISTORY & TERMINOLOGYHISTORY & TERMINOLOGY►German zoologist KARL AUGUST MOBIUS, German zoologist KARL AUGUST MOBIUS,

11stst used the term used the term organula organula

► Around 1920, the term organelle was used Around 1920, the term organelle was used to describe propulsion structures & other to describe propulsion structures & other structures such as ciliatesstructures such as ciliates

► After 1953, the now widely used definition After 1953, the now widely used definition of organelle emerged, after which only of organelle emerged, after which only cellular structures with surrounding cellular structures with surrounding membranes had been considered membranes had been considered organelleorganelle

CELL CELL ORGANELLESORGANELLES

►Cell wallCell wall►Endoplasmic reticulumEndoplasmic reticulum►MitochondriaMitochondria►Nuclear membraneNuclear membrane►Golgi apparatusGolgi apparatus►ChloroplastChloroplast

CELL WALLCELL WALL

►Found in plants, Found in plants, bacteria, fungi, bacteria, fungi, algae, archaeaalgae, archaea

►Not found in Not found in animalanimal

►Located outside Located outside the cell the cell membranemembrane

Composition of cell wallComposition of cell wall►Plant - made up of cellulosePlant - made up of cellulose►Bacteria - made up of peptidoglycanBacteria - made up of peptidoglycan►Archaea - may be of gylcoprotien S Archaea - may be of gylcoprotien S

layer, pseudopeptidoglycan or layer, pseudopeptidoglycan or polysaccharidespolysaccharides

►Fungi - glucoseamine & polymer chitinFungi - glucoseamine & polymer chitin►Algae - glycoprotein & polysaccharideAlgae - glycoprotein & polysaccharide►Diatoms - silicic acidDiatoms - silicic acid

FUNCTIONS OF CELL FUNCTIONS OF CELL WALLWALL

►Structural supportStructural support►ProtectionProtection►RigidityRigidity►PermeabilityPermeability►Filtering mechanismFiltering mechanism►Prevents over expansion when water Prevents over expansion when water

enters the cellenters the cell

ENDOPLASMIC ENDOPLASMIC RETICULUMRETICULUM

► Found in eukaryotic cellFound in eukaryotic cell► Located inside the cell Located inside the cell ► Attached to the nuclear membraneAttached to the nuclear membrane► membrane network of cisternae (sac-like membrane network of cisternae (sac-like

structures) held together by the structures) held together by the cytoskeleton.cytoskeleton.

► Two types of ER :-Two types of ER :-1.1. Rough ERRough ER2.2. Smooth ERSmooth ER

ROUGH ERROUGH ER► Vesicular or tubularVesicular or tubular► Consist of stacks of Consist of stacks of

flatened cisternae flatened cisternae ► Ribosomes are Ribosomes are

found on the outer found on the outer surface of the sacs surface of the sacs or cisternae or cisternae resembling small resembling small beeds beeds

► Synthesizes Synthesizes protiensprotiens

SMOOTH ERSMOOTH ER►Connected to the nuclear envelope Connected to the nuclear envelope ►Consists of tubules & vesicles that Consists of tubules & vesicles that

branch forming a networkbranch forming a network►Network of SER allows increased surface Network of SER allows increased surface

area for the action or storage of key area for the action or storage of key enzymes & products of these enzymesenzymes & products of these enzymes

►Synthesize lipids and steroids, Synthesize lipids and steroids, metabolize carbohydrates & steroids & metabolize carbohydrates & steroids & drug detoxificationdrug detoxification

FUNCTIONS OF ERFUNCTIONS OF ER►Transport chemicals between cells & Transport chemicals between cells &

within cellswithin cells►Provides large surface area for the Provides large surface area for the

organization of chemical reactions and organization of chemical reactions and synthesissynthesis

►Glcosylation ( attachment of Glcosylation ( attachment of oligosaccharides)oligosaccharides)

MITOCHONDRIAMITOCHONDRIA►Found in most eukaryotic cellFound in most eukaryotic cell►Derived from the greek work “mitos” Derived from the greek work “mitos”

meaning thread & “chondrion” meaning thread & “chondrion” meaning granulesmeaning granules

►Range from 0.5-10 micrometer in Range from 0.5-10 micrometer in diameterdiameter

►Described as cellular powerplants as Described as cellular powerplants as they generate ATPthey generate ATP

STRUCTURESTRUCTURE

►Composed of Composed of compartments compartments including outer including outer membrane, membrane, intermembrane intermembrane space, inner space, inner membrane, membrane, cristae & matrixcristae & matrix

FUNCTIONSFUNCTIONS►Produce ATP through respirationProduce ATP through respiration►Apoptosis - programmed cell deathApoptosis - programmed cell death►Regulation of cellular metabolismRegulation of cellular metabolism►Steroid synthesisSteroid synthesis

NUCLEAR MEMBRANENUCLEAR MEMBRANE► Found in eukaryotic cellFound in eukaryotic cell►Double membrane of nucleus enclosing Double membrane of nucleus enclosing

DNA/ any other genetic materialDNA/ any other genetic material► Space between two membranes is Space between two membranes is

perinuclear space & is from 20-100 nm wideperinuclear space & is from 20-100 nm wide►Often referred as nuclear envelopeOften referred as nuclear envelope► Pores on NM regulate exchange of materials Pores on NM regulate exchange of materials

like proteins between nucleus & cytoplasmlike proteins between nucleus & cytoplasm

STRUCTURESTRUCTURE► Inside the inner Inside the inner

membrane, nuclear membrane, nuclear lamina form a network of lamina form a network of filaments playing filaments playing important role in mitosis important role in mitosis & meiosis& meiosis

► Each of the 2 membranes Each of the 2 membranes is composed of lipid is composed of lipid bilayerbilayer

► RER connects with the RER connects with the outer membraneouter membrane

► Both membrane enclose a Both membrane enclose a flattened sac & are flattened sac & are connected at nuclear pore connected at nuclear pore sitessites

FUNCTIONSFUNCTIONS►Play a role in organization & Play a role in organization &

transcriptional activity of chromatintranscriptional activity of chromatin►Regulate in & out movement of Regulate in & out movement of

specific substancesspecific substances►Prevents the nucleus from collapsing & Prevents the nucleus from collapsing &

hence effective in holding nucleus hence effective in holding nucleus together (in plant & animal cells)together (in plant & animal cells)

►Act as security checkAct as security check

GOLGIGOLGI APPARATUSAPPARATUS► found in most found in most

eukaryotic cellseukaryotic cells► identified in 1897 identified in 1897

by the Italian by the Italian physician physician Camillo Camillo GolgiGolgi

► It is protein It is protein packaging plantpackaging plant

► Located near Located near nucleusnucleus

STRUCTURESTRUCTURE►Composed of stacks of membrane Composed of stacks of membrane

bound structures known as cisternaebound structures known as cisternae►Each cisterna comprises a flattened Each cisterna comprises a flattened

membrane disk, and carries Golgi membrane disk, and carries Golgi enzymesenzymes

►The cisternae stack has four functional The cisternae stack has four functional regions: the cis-Golgi network, medial-regions: the cis-Golgi network, medial-Golgi, endo-Golgi, and trans-Golgi Golgi, endo-Golgi, and trans-Golgi networknetwork

FUNCTIONFUNCTION►synthesize a large number of different synthesize a large number of different

macromoleculesmacromolecules► integral in modifying, sorting, and integral in modifying, sorting, and

packaging macromolecules for cell packaging macromolecules for cell secretionsecretion

►Modify chemicals to make them Modify chemicals to make them functionalfunctional

►Secretes chemicals in tiny vesiclesSecretes chemicals in tiny vesicles►Stores chemicals may produce ERStores chemicals may produce ER

CHLOROPLASTCHLOROPLAST►A plastid usually found in plant cellsA plastid usually found in plant cells►Derived from the Greek words Derived from the Greek words chloroschloros, ,

which means green, and which means green, and plastplast, which , which means form or entity.means form or entity.

►They are considered to have They are considered to have originated from cyanobacteria through originated from cyanobacteria through endosymbiosis.endosymbiosis.

►Chloroplasts have their own genomeChloroplasts have their own genome

STRUCTURESTRUCTURE► Composed of double layer of modified Composed of double layer of modified

membrane (protein, chlorophyll, lipid)membrane (protein, chlorophyll, lipid)► Chloroplasts are observed as flat discs Chloroplasts are observed as flat discs

usually 2-10 micrometers in diameter and 1 usually 2-10 micrometers in diameter and 1 micrometer thickmicrometer thick

► The chloroplast is contained by an envelope The chloroplast is contained by an envelope that consists of an inner and an outer that consists of an inner and an outer phospholipid membranephospholipid membrane

► The material within the chloroplast is called The material within the chloroplast is called the stromathe stroma

► It also contains ribosomesIt also contains ribosomes

ULTRASTRUCTUREULTRASTRUCTURE 1. outer membrane1. outer membrane

2. intermembrane 2. intermembrane spacespace3. 3. innerinner membrane membrane (1+2+3: envelope)(1+2+3: envelope)4. stroma (aqueous 4. stroma (aqueous fluid)fluid)5. thylakoid lumen 5. thylakoid lumen (inside of thylakoid)(inside of thylakoid)6. thylakoid membrane6. thylakoid membrane7. granum (stack of 7. granum (stack of thylakoids)thylakoids)8. thylakoid (lamella)8. thylakoid (lamella)9. starch9. starch10. ribosome10. ribosome11. plastidial DNA11. plastidial DNA12. plastoglobule (drop 12. plastoglobule (drop of lipids)of lipids)

FUNCTIONSFUNCTIONS►Contains chlorophyll so responsible for Contains chlorophyll so responsible for

photosynthesisphotosynthesis►Chemical reactions take place for the Chemical reactions take place for the

production of energyproduction of energy