harshini bio project

8/10/2019 Harshini Bio Project

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Cell and its Organells

Name : SSHarshini

Class / Sec : 9thE-2

I.D.No. : 106-0896BIOLOGY PROJECT WORK..


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Introduction of the Cell

The cellis the basic structural, functional and biologicalunit of all known livingorganisms. Cells are the smallestunit of life that is classified as a living thing, and are oftencalled the "building blocks of life".

Cells consist of a protoplasmenclosed within amembrane, which contains many biomolecules suchas proteinsand nucleic acids.[1]Organisms can beclassified as unicellular(consisting of a single cell;including most bacteria) or multicellular(includingplantsand animals). While the number of cells in plants

and animals varies from species to species, humanscontain about 100trillion(1014) cells. Most plant andanimal cells are between 1 and 100 micrometresandtherefore are visible only under the microscope.
http://en.wikipedia.org/wiki/Lifehttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Protoplasmhttp://en.wikipedia.org/wiki/Proteinshttp://en.wikipedia.org/wiki/Nucleic_acidshttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Unicellularhttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Multicellularhttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Animalshttp://en.wikipedia.org/wiki/Orders_of_magnitude_(numbers)http://en.wikipedia.org/wiki/Micrometrehttp://en.wikipedia.org/wiki/Micrometrehttp://en.wikipedia.org/wiki/Orders_of_magnitude_(numbers)http://en.wikipedia.org/wiki/Animalshttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Multicellularhttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Unicellularhttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Nucleic_acidshttp://en.wikipedia.org/wiki/Proteinshttp://en.wikipedia.org/wiki/Protoplasmhttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Life


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Introduction

The cell was discovered by Robert Hookein 1665. The cell theory,first developed in 1839 by Matthias Jakob SchleidenandTheodorSchwann, states that all organisms are composed of one or morecells, that all cells come from preexisting cells, that vital functions ofan organism occur within cells, and that all cells containthe hereditary informationnecessary for regulating cell functions and

for transmitting information to the next generation of cells.Cellsemerged on Earth at least 3.5 billion years ago.

The word cellcomes from the Latincella, meaning "smallroom".[8]It was coined by Robert Hooke in his book Micrographia(1665), in which he compared the corkcells he saw through hismicroscope to the small rooms monks lived in.
http://en.wikipedia.org/wiki/Robert_Hookehttp://en.wikipedia.org/wiki/Cell_theoryhttp://en.wikipedia.org/wiki/Matthias_Jakob_Schleidenhttp://en.wikipedia.org/wiki/Theodor_Schwannhttp://en.wikipedia.org/wiki/Theodor_Schwannhttp://en.wikipedia.org/wiki/Geneticshttp://en.wikipedia.org/wiki/Latinhttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Micrographiahttp://en.wikipedia.org/wiki/Cork_(material)http://en.wikipedia.org/wiki/Cork_(material)http://en.wikipedia.org/wiki/Micrographiahttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Latinhttp://en.wikipedia.org/wiki/Geneticshttp://en.wikipedia.org/wiki/Theodor_Schwannhttp://en.wikipedia.org/wiki/Theodor_Schwannhttp://en.wikipedia.org/wiki/Matthias_Jakob_Schleidenhttp://en.wikipedia.org/wiki/Cell_theoryhttp://en.wikipedia.org/wiki/Robert_Hooke


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Prokaryotic cells

Prokaryoticcells were the first form of life on Earth. Theyare simpler and smaller than eukaryotic cells, and lackmembrane-bound organelles such as the nucleus.Prokaryotes include two of the domains of

life, bacteriaand archaea. The DNA of a prokaryotic cellconsists of a single chromosome that is in direct contactwith the cytoplasm. The nuclear region in the cytoplasmis called the nucleoid.

A prokaryotic cell has three architectural regions:

On the outside, flagellaand piliproject from the cell'ssurface. These are structures (not present in allprokaryotes) made of proteins that facilitate movementand communication between cells.
http://en.wikipedia.org/wiki/Prokaryotehttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Domain_(biology)http://en.wikipedia.org/wiki/Domain_(biology)http://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Archaeahttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Nucleoidhttp://en.wikipedia.org/wiki/Flagellahttp://en.wikipedia.org/wiki/Pilushttp://en.wikipedia.org/wiki/Pilushttp://en.wikipedia.org/wiki/Flagellahttp://en.wikipedia.org/wiki/Nucleoidhttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Archaeahttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Domain_(biology)http://en.wikipedia.org/wiki/Domain_(biology)http://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Prokaryote


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Eukaryotic cells

Plants, animals, fungi, slime moulds, protozoa, and algae areall eukaryotic. These cells are about fifteen times wider than atypical prokaryote and can be as much as a thousand times greaterin volume. The main distinguishing feature of eukaryotes ascompared to prokaryotes is compartmentalization:the presence ofmembrane-bound compartments in which specific metabolic

activities take place. Most important among these is a cell nucleus, amembrane-delineated compartment that houses the eukaryotic cell'sDNA. This nucleus gives the eukaryote its name, which means "truenucleus." Other differences include:

The plasma membrane resembles that of prokaryotes in function,with minor differences in the setup. Cell walls may or may not be

present.
http://en.wikipedia.org/wiki/Eukaryotehttp://en.wikipedia.org/wiki/Cellular_compartmenthttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Cellular_compartmenthttp://en.wikipedia.org/wiki/Eukaryote


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Eukaryotic cells

The eukaryotic DNA is organized in one or more linear molecules,called chromosomes, which are associated with histoneproteins. Allchromosomal DNA is stored in the cell nucleus, separated from thecytoplasm by a membrane. Some eukaryotic organellessuchas mitochondriaalso contain some DNA.

Many eukaryotic cells are ciliatedwithprimary cilia. Primary cilia

play important roles in chemosensation, mechanosensation, andthermosensation. Cilia may thus be "viewed as a sensorycellular antennaethat coordinates a large number of cellularsignaling pathways, sometimes coupling the signaling to ciliarymotility or alternatively to cell division and differentiation."

Eukaryotes can move using motile ciliaor flagella. Eukaryotic

flagella are less complex than those of prokaryotes.
http://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Organellehttp://en.wikipedia.org/wiki/Mitochondriahttp://en.wikipedia.org/wiki/Ciliumhttp://en.wikipedia.org/wiki/Mechanosensationhttp://en.wikipedia.org/wiki/Antenna_(biology)http://en.wikipedia.org/wiki/Ciliahttp://en.wikipedia.org/wiki/Ciliahttp://en.wikipedia.org/wiki/Antenna_(biology)http://en.wikipedia.org/wiki/Mechanosensationhttp://en.wikipedia.org/wiki/Ciliumhttp://en.wikipedia.org/wiki/Mitochondriahttp://en.wikipedia.org/wiki/Organellehttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/Chromosome


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Sub cellular Components

All cells, whether prokaryoticor eukaryotic, havea membranethat envelops the cell, separates its interiorfrom its environment, regulates what moves in and out(selectively permeable), and maintains the electricpotential of the cell. Inside the membrane,

a saltycytoplasmtakes up most of the cell volume. Allcells (except red blood cellswhich lack a cell nucleusand most organelles to accommodate maximum spacefor hemoglobin) possessDNA, the hereditary materialof genes, and RNA, containing the information

necessary to buildvarious proteinssuch as enzymes,the cell's primary machinery. There are also other kindsof biomoleculesin cells. This article lists these primarycomponents of the cell, then briefly describes theirfunction.
http://en.wikipedia.org/wiki/Prokaryotichttp://en.wikipedia.org/wiki/Eukaryotichttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Membrane_potentialhttp://en.wikipedia.org/wiki/Membrane_potentialhttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Red_blood_cellhttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Gene_expressionhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Biomoleculehttp://en.wikipedia.org/wiki/Biomoleculehttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Gene_expressionhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Red_blood_cellhttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Membrane_potentialhttp://en.wikipedia.org/wiki/Membrane_potentialhttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Eukaryotichttp://en.wikipedia.org/wiki/Prokaryotic


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Membrane

The cell membrane, or plasma membrane, surrounds the cytoplasmof a cell. In animals, the plasma membrane is the outer boundary ofthe cell, while in plants and prokaryotes it is usually covered bya cell wall. This membrane serves to separate and protect a cellfrom its surrounding environment and is made mostly from a doublelayer of phospholipids, which

are amphiphilic(partly hydrophobicand partly hydrophilic). Hence,the layer is called aphospholipid bilayer, or sometimes a fluidmosaic membrane. Embedded within this membrane is a varietyof proteinmolecules that act as channels and pumps that movedifferent molecules into and out of the cell. The membrane is said tobe 'semi-permeable', in that it can either let a substance(moleculeor ion) pass through freely, pass through to a limitedextent or not pass through at all. Cell surface membranes alsocontain receptorproteins that allow cells to detect external signalingmolecules such as hormones.
http://en.wikipedia.org/wiki/Cell_wallhttp://en.wikipedia.org/wiki/Lipid_bilayerhttp://en.wikipedia.org/wiki/Lipid_bilayerhttp://en.wikipedia.org/wiki/Amphiphilichttp://en.wikipedia.org/wiki/Hydrophobichttp://en.wikipedia.org/wiki/Hydrophilichttp://en.wikipedia.org/wiki/Phospholipid_bilayerhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Receptor_(biochemistry)http://en.wikipedia.org/wiki/Hormonehttp://en.wikipedia.org/wiki/Hormonehttp://en.wikipedia.org/wiki/Receptor_(biochemistry)http://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Phospholipid_bilayerhttp://en.wikipedia.org/wiki/Hydrophilichttp://en.wikipedia.org/wiki/Hydrophobichttp://en.wikipedia.org/wiki/Amphiphilichttp://en.wikipedia.org/wiki/Lipid_bilayerhttp://en.wikipedia.org/wiki/Lipid_bilayerhttp://en.wikipedia.org/wiki/Cell_wall


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Genetic material

Two different kinds of genetic material exist: deoxyribonucleicacid(DNA) and ribonucleic acid(RNA). Most cells use DNA for theirlong-term information storage. The biological information containedin an organism is encodedin its DNA sequence. RNA is used forinformation transport (e.g., mRNA) and enzymaticfunctions(e.g., ribosomalRNA). Transfer RNA(tRNA) molecules are used to

add amino acids during proteintranslation.Prokaryotic genetic material is organized in a simple circular DNAmolecule (the bacterial chromosome) in the nucleoid regionof thecytoplasm. Eukaryotic genetic material is divided into different, linearmolecules called chromosomesinside a discrete nucleus, usuallywith additional genetic material in some organelles

like mitochondriaand chloroplasts(see endosymbiotic theory).
http://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/MRNAhttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/Ribosomehttp://en.wikipedia.org/wiki/Transfer_RNAhttp://en.wikipedia.org/wiki/Translationhttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Nucleoid_regionhttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Mitochondriahttp://en.wikipedia.org/wiki/Chloroplastshttp://en.wikipedia.org/wiki/Endosymbiotic_theoryhttp://en.wikipedia.org/wiki/Endosymbiotic_theoryhttp://en.wikipedia.org/wiki/Chloroplastshttp://en.wikipedia.org/wiki/Mitochondriahttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Nucleoid_regionhttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Translationhttp://en.wikipedia.org/wiki/Transfer_RNAhttp://en.wikipedia.org/wiki/Ribosomehttp://en.wikipedia.org/wiki/Enzymehttp://en.wikipedia.org/wiki/MRNAhttp://en.wikipedia.org/wiki/Genetic_codehttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/DNA


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Genetic material

A human cell has genetic material contained in the cellnucleus(the nuclear genome) and in the mitochondria(the mitochondrial genome). In humans the nuclear genome isdivided into 46 linear DNA molecules called chromosomes, including22 homologouschromosome pairs and a pair of sex chromosomes.The mitochondrial genome is a circular DNA molecule distinct from

the nuclear DNA. Although the mitochondrial DNAis very smallcompared to nuclear chromosomes, it codes for 13 proteins involvedin mitochondrial energy production and specific tRNAs.

Foreign genetic material (most commonly DNA) can also beartificially introduced into the cell by a process called transfection.This can be transient, if the DNA is not inserted into the

cell'sgenome, or stable, if it is. Certain virusesalso insert theirgenetic material into the genome.
http://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Mitochondrial_genomehttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Homologous_chromosomehttp://en.wikipedia.org/wiki/Sex_chromosomeshttp://en.wikipedia.org/wiki/Mitochondrial_DNAhttp://en.wikipedia.org/wiki/Transfectionhttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Transfectionhttp://en.wikipedia.org/wiki/Mitochondrial_DNAhttp://en.wikipedia.org/wiki/Sex_chromosomeshttp://en.wikipedia.org/wiki/Homologous_chromosomehttp://en.wikipedia.org/wiki/Chromosomehttp://en.wikipedia.org/wiki/Mitochondrial_genomehttp://en.wikipedia.org/wiki/Genomehttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Cell_nucleus


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Organells

Organelles are parts of the cell which are adapted and/orspecialized for carrying out one or more vital functions,analogous to the organsof the human body (such as theheart, lung, and kidney, with each organ performing adifferent function). Both eukaryotic and prokaryotic cells

have organelles, but prokaryotic organelles are generallysimpler and are not membrane-bound.

There are several types of organelles in a cell. Some(such as the nucleusand golgi apparatus) are typicallysolitary, while others (such

as mitochondria, chloroplasts, peroxisomesandlysosomes) can be numerous (hundreds to thousands).The cytosolis the gelatinous fluid that fills the cell andsurrounds the organelles.
http://en.wikipedia.org/wiki/Organ_(anatomy)http://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Mitochondriahttp://en.wikipedia.org/wiki/Chloroplastshttp://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Lysosomeshttp://en.wikipedia.org/wiki/Lysosomeshttp://en.wikipedia.org/wiki/Cytosolhttp://en.wikipedia.org/wiki/Cytosolhttp://en.wikipedia.org/wiki/Lysosomeshttp://en.wikipedia.org/wiki/Lysosomeshttp://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Chloroplastshttp://en.wikipedia.org/wiki/Mitochondriahttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Organ_(anatomy)


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Eukaryotic :

Cell nucleus: A cell's information center, the cell nucleusis themost conspicuous organelle found in a eukaryoticcell. It houses thecell'schromosomes, and is the place where almostall DNAreplication and RNAsynthesis (transcription) occur. Thenucleus is spherical and separated from the cytoplasm by a doublemembrane called the nuclear envelope. The nuclear envelope

isolates and protects a cell's DNA from various molecules that couldaccidentally damage its structure or interfere with its processing.During processing, DNAis transcribed, or copied into aspecial RNA, called messenger RNA(mRNA). This mRNA is thentransported out of the nucleus, where it is translated into a specificprotein molecule. The nucleolusis a specialized region within the

nucleus where ribosome subunits are assembled. In prokaryotes,DNA processing takes place in the cytoplasm.
http://en.wikipedia.org/wiki/Cell_nucleushttp://en.wikipedia.org/wiki/Eukaryotichttp://en.wikipedia.org/wiki/Chromosomeshttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/Nuclear_envelopehttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Messenger_RNAhttp://en.wikipedia.org/wiki/Nucleolushttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Nucleolushttp://en.wikipedia.org/wiki/Messenger_RNAhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Nuclear_envelopehttp://en.wikipedia.org/wiki/Transcription_(genetics)http://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Chromosomeshttp://en.wikipedia.org/wiki/Eukaryotichttp://en.wikipedia.org/wiki/Cell_nucleus


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Eukaryotic

Mitochondria and Chloroplasts: the powergenerators: Mitochondriaare self-replicating organellesthat occur in various numbers, shapes, and sizes in thecytoplasm of all eukaryotic cells. Mitochondria play a

critical role in generating energy in the eukaryoticcell. Respirationoccurs in the cell mitochondria, whichgenerate the cell's energy by oxidative phosphorylation,using oxygento release energy stored in cellularnutrients (typically pertaining to glucose) to

generateATP. Mitochondria multiply by binary fission,like prokaryotes. Chloroplasts can only be found inplants and algae, and they capture the sun's energy tomake ATP.
http://en.wikipedia.org/wiki/Mitochondrionhttp://en.wikipedia.org/wiki/Cellular_respirationhttp://en.wikipedia.org/wiki/Oxidative_phosphorylationhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Adenosine_triphosphatehttp://en.wikipedia.org/wiki/Binary_fissionhttp://en.wikipedia.org/wiki/Binary_fissionhttp://en.wikipedia.org/wiki/Adenosine_triphosphatehttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxidative_phosphorylationhttp://en.wikipedia.org/wiki/Cellular_respirationhttp://en.wikipedia.org/wiki/Mitochondrion


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Eukaryotic

Endoplasmic reticulum: The endoplasmicreticulum(ER) is a transport network for moleculestargeted for certain modifications and specificdestinations, as compared to molecules that float freely

in the cytoplasm. The ER has two forms: the rough ER,which has ribosomes on its surface that secrete proteinsinto the ER, and the smooth ER, which lacks ribosomes.The smooth ER plays a role in calcium sequestrationand release. (See Endoplasmic reticulum)

Golgi apparatus: The primary function of the Golgiapparatus is to process and packagethe macromoleculessuch as proteinsand lipidsthat aresynthesized by the cell. (See Golgi apparatus)
http://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Macromoleculehttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Lipidhttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Lipidhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Macromoleculehttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Endoplasmic_reticulum


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Eukaryotic

Lysosomes and Peroxisomes: Lysosomescontain digestiveenzymes(acid hydrolases). They digest excess or worn-out organelles, food particles, andengulfed virusesor bacteria. Peroxisomeshave enzymes that rid thecell of toxic peroxides. The cell could not house these destructiveenzymes if they were not contained in a membrane-bound system.

(See Lysosomeand Peroxisome)Centrosomethe cytoskeleton organiser:The centrosomeproduces the microtubulesof a cell a keycomponent of the cytoskeleton. It directs the transport throughthe ERand the Golgi apparatus. Centrosomes are composed oftwo centrioles, which separate during cell divisionand help in the

formation of the mitotic spindle. A single centrosome is present inthe animal cells. They are also found in some fungi and algae cells.(SeeCentrosome)
http://en.wikipedia.org/wiki/Lysosomehttp://en.wikipedia.org/wiki/Digestive_enzymehttp://en.wikipedia.org/wiki/Digestive_enzymehttp://en.wikipedia.org/wiki/Hydrolasehttp://en.wikipedia.org/wiki/Organellehttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Peroxisomehttp://en.wikipedia.org/wiki/Peroxidehttp://en.wikipedia.org/wiki/Lysosomehttp://en.wikipedia.org/wiki/Peroxisomehttp://en.wikipedia.org/wiki/Centrosomehttp://en.wikipedia.org/wiki/Microtubuleshttp://en.wikipedia.org/wiki/Cytoskeletonhttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Centrioleshttp://en.wikipedia.org/wiki/Cell_divisionhttp://en.wikipedia.org/wiki/Mitotic_spindlehttp://en.wikipedia.org/wiki/Animal_cellhttp://en.wikipedia.org/wiki/Centrosomehttp://en.wikipedia.org/wiki/Centrosomehttp://en.wikipedia.org/wiki/Animal_cellhttp://en.wikipedia.org/wiki/Mitotic_spindlehttp://en.wikipedia.org/wiki/Cell_divisionhttp://en.wikipedia.org/wiki/Centrioleshttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Cytoskeletonhttp://en.wikipedia.org/wiki/Microtubuleshttp://en.wikipedia.org/wiki/Centrosomehttp://en.wikipedia.org/wiki/Peroxisomehttp://en.wikipedia.org/wiki/Lysosomehttp://en.wikipedia.org/wiki/Peroxidehttp://en.wikipedia.org/wiki/Peroxisomehttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Virushttp://en.wikipedia.org/wiki/Organellehttp://en.wikipedia.org/wiki/Hydrolasehttp://en.wikipedia.org/wiki/Digestive_enzymehttp://en.wikipedia.org/wiki/Digestive_enzymehttp://en.wikipedia.org/wiki/Lysosome


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Eukaryotic

Vacuoles: Vacuolesstore food and waste.Some vacuoles store extra water. Theyare often described as liquid filled space

and are surrounded by a membrane.Some cells, most notablyAmoeba, havecontractile vacuoles, which can pumpwater out of the cell if there is too much

water. The vacuoles of eukaryotic cells areusually larger in those of plants thananimals. (See Vacuole)
http://en.wikipedia.org/wiki/Vacuolehttp://en.wikipedia.org/wiki/Amoebahttp://en.wikipedia.org/wiki/Vacuolehttp://en.wikipedia.org/wiki/Vacuolehttp://en.wikipedia.org/wiki/Amoebahttp://en.wikipedia.org/wiki/Vacuole


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Eukaryotic and Prokaryotic

Ribosomes: The ribosomeis a largecomplex of RNAand proteinmolecules.They each consist of two subunits, and act

as an assembly line where RNA from thenucleus is used to synthesise proteinsfrom amino acids. Ribosomes can befound either floating freely or bound to a

membrane (the rough endoplasmaticreticulum in eukaryotes, or the cellmembrane in prokaryotes)
http://en.wikipedia.org/wiki/Ribosomehttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Ribosome


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Structure outside the cell

membraneMany cells also have structures which exist wholly or partiallyoutside the cell membrane. These structures are notable becausethey are not protected from the external environment by theimpermeable cell membrane. In order to assemble these structures,their components must be carried across the cell membrane byexport processes.

Cell wall: Many types of prokaryotic and eukaryotic cells have a cellwall. The cell wall acts to protect the cell mechanically andchemically from its environment, and is an additional layer ofprotection to the cell membrane. Different types of cell have cellwalls made up of different materials; plant cell walls are primarilymade up of pectin, fungi cell walls are made up of chitin and bacteriacell walls are made up of peptidoglycan.
http://en.wikipedia.org/wiki/Cell_wallhttp://en.wikipedia.org/wiki/Cell_wallhttp://en.wikipedia.org/wiki/Cell_wallhttp://en.wikipedia.org/wiki/Cell_wall


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Prokaryotic

Capsule :A gelatinous capsule is present in some bacteria outside the cellmembrane and cell wall. The capsule may be polysaccharideasin pneumococci, meningococci or polypeptideas Bacillusanthracisor hyaluronic acidas in streptococci. (See Bacterial capsule.)Capsules are not marked by normal staining protocols and can be detectedby India inkor Methyl blue; which allows for higher contrast between thecells for observation.

Flagella : Flagella are organelles for cellular mobility. The bacterialflagellum stretches from cytoplasm through the cell membrane(s) andextrudes through the cell wall. They are long and thick thread-likeappendages, protein in nature. Are most commonly found in bacteria cellsbut are found in animal cells as well.

Fimbriae (pili) : They are short and thin hair-like filaments, formed ofprotein called pilin (antigenic). Fimbriaeare responsible for attachment of

bacteria to specific receptors of human cell (adherence). There are specialtypes of pili called (sex pili) involved in conjunction.
http://en.wikipedia.org/wiki/Polysaccharidehttp://en.wikipedia.org/wiki/Polypeptidehttp://en.wikipedia.org/wiki/Bacillus_anthracishttp://en.wikipedia.org/wiki/Bacillus_anthracishttp://en.wikipedia.org/wiki/Hyaluronic_acidhttp://en.wikipedia.org/wiki/Streptococcihttp://en.wikipedia.org/wiki/Bacterial_capsulehttp://en.wikipedia.org/wiki/India_inkhttp://en.wikipedia.org/wiki/Methyl_bluehttp://en.wikipedia.org/wiki/Fimbria_(bacteriology)http://en.wikipedia.org/wiki/Fimbria_(bacteriology)http://en.wikipedia.org/wiki/Methyl_bluehttp://en.wikipedia.org/wiki/India_inkhttp://en.wikipedia.org/wiki/Bacterial_capsulehttp://en.wikipedia.org/wiki/Streptococcihttp://en.wikipedia.org/wiki/Hyaluronic_acidhttp://en.wikipedia.org/wiki/Bacillus_anthracishttp://en.wikipedia.org/wiki/Bacillus_anthracishttp://en.wikipedia.org/wiki/Polypeptidehttp://en.wikipedia.org/wiki/Polysaccharide


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