Presentation on theme: "Comparative study of typical prokaryotic cell and eukaryotes"— Presentation transcript:
1 Comparative study of typical prokaryotic cell and eukaryotes ByDR SAMUEL AGUAZIM
2 STRUCTURE, FUNCTION & GROWTH OF PROKARYOTIC & EUKARYOTIC CELLS
3 Prokaryotic and Eukaryotic Cells . All living creatures are made up of CELLS , small membrane bound units filled with aqueous solutions of chemicals, which have the ability to create copies of themselves by growing and dividing.
4 Living organisms can be classified into 3 major domains: Prokaryotes*Bacteria*ArchaeaEukaryotes*Plant cells*Animal cellsProkaryotes and Eukaryotes are 2 distinct cell types with STRUCTURAL differences
5 The Prokaryotic CellThe Prokaryotic Cell Simply stated, prokaryotes are molecules surrounded by a membrane and cell wall.
6 Prokaryotes Lack a membrane bound nucleus enclosing the DNA DNA is present as a single circular molecule called a BACTERIAL CHROMOSOMEDNA is naked having no associated histone proteinsNo membrane bound organellesApart from the DNA nucleoid, there is little internal structure apart from dissolved substances and a large number of RIBOSOMES essential for PROTEIN SYNTHESISThe cytosol is an effective site for bacterial cell metabolism. This allows bacteria to adapt quickly to changing nutritional conditions, but means the regulation of genetic and metabolic activity has to be tightly regulated.Divide by BINARY FISSIONSome prokaryotic cells have external whip-like FLAGELLA for locomotion or hair like PILI for adhesion.Prokaryotic cells come in multiple shapes: cocci (round), baccilli (rods), and spirilla or spirochetes (helical cells).
7 External Prokaryotic Structures Cell wall Contains PEPTIDOGLYCAN (only found in bacteria). Large complex molecule consisting of polysaccharide polymers cross-linked by short chains of amino acidsCapsulesSometimes the cell wall is further surrounded by a gelatinous polysaccharide sheath called an attach CAPSULE , GLYCOCALYX or SLIME LAYERPlasma MembraneBasic structure of the phospholipid bilayer is the same for all bacteriaFlagella Motile bacteria usually have long, thin appendages called FLAGELLA . These protein sub-units are used to propel bacteria through liquids
8 Pili or FimbraeA pilus ( Latin ; plural : pili ) is a hairlike protein structure on the surface of a bacterial cell, required for bacterial conjugation (transfer of genetic material)A fimbrium (Latin; plural: fimbria ) is a short pilus that is used to attach the cell to a surface. Mutant bacteria that lack fimbria cannot adhere to their usual target surfaces and, thus, cannot cause diseases
9 Spores & CystsThese are produced by some bacteria to survive unfavourable environmental conditions. Dormant forms are metabolically inactive and only germinate under suitable conditionsENDOSPORES : a dormant , tough, non-reproductive structure produced by a small number of bacteria . The primary function of most endospores is to ensure the survival of a bacterium through periods of environmental stress. They are therefore resistant to ultraviolet and gamma radiation , desiccation , lysozyme , temperature , starvation , and chemical disinfectants . Endospores are commonly found in soil and water, where they may survive for long periods of time e.g. Clostridium (tetanus, gas gangrene), Bacillus (anthrax)CYSTS : also dormant, but unlike endospores are not resistant to heating at high temperatures
10 Lipoprotein bilayer without sterols StructureChemical CompositionFunctionCell wallPeptidoglycanSugar backbone with peptide side chains that are cross-linkedGives rigid support, protects against osmotic pressure;is the site of action of penicillins andcephalosporins and is degraded by lysozyme.Outer membrane of gram-negative bacteriaLipid AToxic component of endotoxin.PolysaccharideSurface fibers of gram- Teichoic acid positive bacteria Gives rigid support, protects against osmotic pressure; is the site of action of penicillins and cephalosporins and is degraded by lysozyme. Toxic component of endotoxin.Major surface antigen used frequently in laboratorydiagnosis.Cytoplasmic membraneLipoprotein bilayer without sterolsSite of oxidative and transport enzymes.
11 RibosomeRNA and protein in 50S and 30S Protein subunitsProtein synthesis; site of action of aminoglycosides,subunits erythromycin, tetracyclines, and chloramphenicol.NucleoidDNAGenetic material.Mesosomelnvagination of plasma membraneParticipates in cell division and secretion.PeriplasmSpace between plasmamembrane and outer membraneContains many hydrolytic enzymes, includingP-lactamases.
12 Non-essential components CapsulePolysaccharideProtects against phagocytosisPilus or fimbriaGlycoproteinTwo types: (1) mediates attachment to cell surfaces;(2) sex pilus mediates attachment of two bacteriaduring conjugationFlagellumProteinMotility.SporeKeratinlike coat, dipicolinic acidProvides resistance to dehydration, heat, andchemicals.PlasmidDNAContains a variety of genes for antibiotic resistanceand toxins.
13 GranuleGlycogen, lipids, polyphosphates.Site of nutrients in cytoplasm.GlycocalyxPolysaccharideMediates adherence to surfaces.
14 Classifying Prokarotes Main method is using the GRAM’S STAINThis separates bacteria into GRAM-POSITIVE (purple) and GRAM-NEGATIVE (red) depending on the percentage of PEPTIDOGLYCAN in the cell walls- GRAM-POSITIVE bacteria have a cell wall only 1 layer thick- GRAM-NEGATIVE bacteria have a cell wall several layers thick
15 Differences between cell wall of Gram positive and Gram negative bacteria CharacterGram positiveGram negativeThicknessThickerThinnerPeriplasmic spaceAbsentPresentLipidsAbsent or smallTeichoic acidPeptidoglycan16- 80nm2nm
16 EukaryotesMore complex multicellular organisms e.g. plants, animals, fungi and also many single-celled organisms e.g. amoeba, yeastPossess an NUCLEUS and other organelles all of which are surrounded by a MEMBRANE , which divided the cell up into compartmentsCOMPARTMENTALISATION: very important !ADVANTAGES:Molecules are ‘concentrated’ together, increases rate of reactionsKeeps reactive molecules away from other parts of the cell that may be affected by themLarge work surface area … many enzymes are bound in membranes
17 Eukaryotes The basic eukaryotic cell contains the following: - membrane-bound nucleus- plasma membrane- glycocalyx (components external to the plasmamembrane)- cytoplasm (semifluid)- cytoskeleton – microfilaments, intermediate filaments and microtubules that suspend organelles, give shape, and allow motion .- presence of characteristic membraneenclosed subcellular organelles e.g. mitochondria, golgi, rER, sER etc
18 Plant & Animal Cells For ANIMAL CELLS only: For PLANT CELLS only: Peroxisomes & Lysosomes often presentSome have microvilli on their surfaceCentrioles organise spindle fibres during cell divisionFor PLANT CELLS only:Cell walls made from celluloseCommunication with neighbouring cells occurs through plasmodesmataUsually a large central vacuolePhotosynthesis occurs in cells containing chloroplasts
19 Plasma Membrane Plasma Membrane A lipid/protein/carbohydrate complex, providing a barrier and containing transport and signalling systems.
20 NucleusNucleusDouble membrane surrounding the chromosomes and the nucleolus. Pores allow specific communication with the cytoplasm. The nucleolus is a site for synthesis of RNA making up the ribosome
21 Mitochondria Mitochondria Surrounded by a double membrane with a series of folds called cristae.Functions in energy production through metabolism.Contains its own DNA, and is believed to have originated as a captured bacterium.
22 Rough endoplasmic reticulum (RER) A network of interconnected membranes forming channels within the cell.Covered with ribosomes (causing the rough appearance) which are in the process of synthesizing proteins for secretion or localization in membranes.RibosomesProtein and RNA complex responsible for protein synthesis
23 Golgi Apparatus Golgi apparatus *A series of stacked membranes. Vesicles (small membrane surrounded bags) carry materials from the RER to the Golgi apparatus.*Vesicles move between the stacks while the proteins are processedto a mature form.*Vesicles then carry newly formed membrane and secreted proteins to their final destinations including secretion or membrane localisation.
24 Centrioles Centrioles Centrioles are found only in animal cells. They function in cell division.
25 LysosymesLysosymesA membrane bound organelle that is responsible for degrading proteins and membranes in the cell, and also helps degrade materials ingested by the cell.
26 Peroxisomes Peroxisomes or Microbodies Produce and degrade hydrogen peroxide, a toxic compound that can be produced during metabolism
27 Chloroplasts Chloroplasts Surrounded by a double membrane, containing stacked thylakoid membranes.Responsible for photosynthesis, the trapping of light energy for the synthesis of sugars.Contains DNA, and like mitochondria is believed to have originated as a captured bacterium.
28 VacuolesVacuolesMembrane surrounded “bags” that contain water and storage materials in plants.
29 Cell wallPlants have a rigid cell wall in addition to their cell membranes. They provide support for the plant.
30 Similarities between P & E cells Prokaryotes & Eukaryotes are CHEMICALLY & METABOLICALLY similar:Both have genetic materialBoth have a cell membraneBoth have a cytosolBoth have ribosomesBoth contain nucleic acids, proteins, carbohydrates & lipidsBoth use similar reactions for storing energy and metabolic activities e.g. building proteins
31 Differences between P & E cells main differences are structural ProkaryoteseukaryotesNo membrane bound organelles nucluesMembrane bound nucleusCell walls made of peptidoglycan (Thickness of wall depends on whether the cell is Gram +ve or –ve)Cell walls, if present, made of cellulose (chitin in fungi)No membrane bound organellesMembrane bound organelles (compartmentalisation)Have pili & fimbriae (for adhesion) and flagella (for propulsion)Have cilia or flagella (for movement)Mucilaginous capsuleNo mucilaginous capsule present (numerous internal structures present including microtubules, ER, Golgi, secretory vesicles etc)ranges from 0.5um to 100um bound nucleusCell size ranges from 10 – 150um Cell sizeMain differences are STRUCTURAL :
32 Comparison of prokaryotic and eukaryotic cells ProkaryotesEukaryotesOrganismsMonera: Eubacteria & archebacteriaProtists, fungi, plants and animalsLevel of organizationSingle celledSingle celled (protists mostly) or multicellular usually with tissues and organsTypical cell sizeSmall(1-10microns)Large( microns)Celll wallAlmost all have cell walls(murein)Fungi and plants(cellulose and chitin): none in animlasOrganellesUsually nonemany different ones with specialized functionsMetabolismAnaerobic and aerobic: diverseMostly aerobic
33 Comparison of prokaryotic and eukaryotic cells Genetic materialSingle circular double stranded DNAComplex chromosomes usually in pairs: each with a single double stranded DNA molecule and associatied proteins contained in a nucleusMode of divisionBinary fission mostly: buddingMitosis and meiosis using a spindle: followed by cytokinesis