Characteristics of Prokaryotic and Eukaryotic Cells PDF

Characteristics of Prokaryotic and Eukaryotic Cells WSAqma_UKM 1 Characteristics of Prokaryotic and Eukaryotic Cells Basic Cell Types Prokaryotic Cells Eukaryotic Cells Evolution of Endosymbiosis WSAqma_UKM...

Characteristics of Prokaryotic and Eukaryotic Cells WSAqma_UKM 1 Characteristics of Prokaryotic and Eukaryotic Cells Basic Cell Types Prokaryotic Cells Eukaryotic Cells Evolution of Endosymbiosis WSAqma_UKM 2 Microorganisms Proka/Euka? Bacteria Archea Algae Fungi -mushroom -molds -yeast Protozoa Parasites-helminth Virus WSAqma_UKM 3 Relative sizes of objects WSAqma_UKM 4 Classification- 3 Domains WSAqma_UKM 5  Basic Cell Types Prokaryote: single-celled organisms, and all are bacteria. Eukaryote: single-celled or multi- cellular organisms Pro = before Eu = true Karyon = nucleus WSAqma_UKM 6 Comparison between prokaryotic and eukaryotic cells WSAqma_UKM 7  J I H G F A E B D C WSAqma_UKM 8 WSAqma_UKM 9 WSAqma_UKM 10  Size, Shape and Arrangement Prokaryotes are among the smallest of all organisms Prokaryotes range from 0.2 – 2.0 µm in diameter and from 2.0 – 8.0 µm in length Exception: 1991- Epulopiscium fishelsoni is a bacterial symbiont of sturgeon fish (80 µm in diameter and 600 µm in length 1999- Thiomargarita namibiensis was the largest bacterium known (100-300 µm in diameter ) 1 mm = X µm 1 mL = Y µL WSAqma_UKM 11 TASK: Identify bacteria species for each shape Basic Cell Types: common bacterial shapes Pleomorphic-have many shape WSAqma_UKM 12 Arrangements of Bacteria: Cocci in pairs (diplococci): Neisseria sp. Cocci in chains (streptococci): Streptococcus sp. Rods in chains: Lactobacillus sp. WSAqma_UKM 13 Cocci in clusters: Staphylococcus sp. Caulobacter (2400X) Haloarcula Stella WSAqma_UKM 14  TYPICAL PROKARYOTIC CELL Structurally, bacterial cells consist of the following: 1. Cell wall 2. Cell membrane, usually surrounded by a cell wall 3. Internal cytoplasm with ribosomes, nuclear region, and in some cases granules and/or vesicles 4. External structure: Capsules, flagella, and pili WSAqma_UKM 15  1) The Cell Wall Lies outside the cell membrane in nearly all bacteria Two important functions: 1. Maintains the characteristic shape 2. Prevents the cell from bursting when fluids flow into the cell by osmosis Components of bacterial cell walls: 1. Peptidoglycan (murein) 2. Lipopolysaccharide (LPS) 3. Outer membrane 4. Periplasmic space WSAqma_UKM 16 Components of Bacterial Cell Walls: Peptidoglycan Peptidoglycan (murein): The single most important component 1) This polymer is made up of two alternating sugar units: N-acetylglucosamine (NAG) N-acetylmuramic acid (NAM) 2) The sugars are joined by short peptide chains that consist of four amino acids (tetrapeptides) WSAqma_UKM 17 GRAM -ve PEPTIDOGLYCAN LAYER Tetrapeptide chain GRAM +ve WSAqma_UKM 18  Cell Wall & Osmotic Pressure Intracellular and external environment strive for isosmotic equilibrium. Osmotic pressure, refers to that required to hold back the net movement of water. Hypotonic environments promote “osmolysis”; unless there’s a rigid cell wall. Hypertonic environments promote “plasmolysis” WSAqma_UKM 19  Distinguishing Bacteria by Cell Walls Gram-positive Bacteria have a relatively thick layer of peptidoglycan (60-90%) Gram-negative Bacteria have a more complex cell wall with a thin layer of peptidoglycan (10-20%) Acid-fast Bacteria is thick, like that of gram- positive bacteria, but has much less peptidoglycan and about 60% lipid WSAqma_UKM 20 WSAqma_UKM 21  Teichoic Acid An additional component found in cell walls of Gram-positive bacteria Consists of glycerol, phosphates, and ribitol (sugar alcohol) This polymer extends beyond the rest of the cell wall Two functions: 1. Attachment site for bacteriophages 2. Passageway for movement of ions in/out of cell WSAqma_UKM 22  Components of cell walls: Outer Membrane (OM) A bilayer membrane found in Gram- negative bacteria Forms the outermost layer of the cell wall; is attached to the peptidoglycan by a continuous layer of lipoprotein molecules Proteins called porins form channels through the OM OM has surface antigens and receptors WSAqma_UKM 23  Lipopolysaccharide (LPS) An important component of the OM Also called endotoxin; used to ID Gram- negative bacteria Released when the cell walls of bacteria are broken down Consists of polysaccharides and Lipid A WSAqma_UKM 24 Lipopolysaccharide layer (LPS) also called as endotoxin - bacteria Gram -ve WSAqma_UKM 25 Components of cell walls: Periplasmic Space The area between the cytoplasmic membrane and the plasma membrane in Gram-negative bacteria Active area of cell metabolism Contains the cell wall, digestive enzymes and transport proteins Gram-positive bacteria lack both an OM and a periplasmic space WSAqma_UKM 26  Cell Wall (Gram +) WSAqma_UKM 27  Cell Wall (Gram -) (w/ Outer Membrane) Braun’s lipoprotein core (LPS = endotoxin) Periplasmic space WSAqma_UKM 28  Acid-Fast Bacteria Found in bacteria that belong to the genus, Mycobacterium sp. Cell wall is mainly composed of lipid Lipid component is mycolic acid Acid-fast bacteria stain gram-positive WSAqma_UKM 29 Gram staining WSAqma_UKM 30 WSAqma_UKM 31  Wall-Deficient Organisms Bacteria that belong to the genus Mycoplasma have no cell walls They are protected from osmotic swelling and bursting by a strengthened cell membrane that contains sterols Wall deficient strains are called L-forms WSAqma_UKM 32  Controlling BACTERIA by DAMAGING CELL WALL 1)Penicillin: blocks the final stages of peptidoglycan synthesis (if antibiotic present when bacteria cells are dividing-----INCOMPLETE WALLS----BACTERIA DIE 2)Lysozyme: digest peptidoglycan (ex: in tears) Enzymes---prevent bacteria from entering the body---defense against infections WSAqma_UKM 33  2) The cell membrane Or plasma membrane Forms the boundary between cell and its environment Dynamic, constantly changing Consist mainly: phospholipid and proteins Fluid-mosaic model (1972) 1. phospholipids in a fluid state 2. proteins are dispersed among lipid molecules in the membrane WSAqma_UKM 34  Cell membranes functions 1. Regulate the movement of materials into and out of a cell-transport mechanism 2. Synthesizes cell wall components: DNA replication, secretes proteins, carries on respiration and captures energy as ATP 3. Contains bases of flagella 4. Some proteins in the cell membrane respond to chemical substances in the environment 5. Able to communicate with other cells, identifying themselves and sharing information. WSAqma_UKM 35  Cell membranes To perform these roles, the plasma membrane needs lipids, which make a semi-permeable barrier between the cell and its environment. It also needs proteins, which are involved in cross-membrane transport and cell communication, and carbohydrates (sugars and sugar chains), which decorate both the proteins and lipids and help cells recognize each other. WSAqma_UKM 36 The Basic Structural Component of the Membrane: Phospholipid Molecule WSAqma_UKM 37  The Fluid-Mosaic Model of the Membrane Structure plasma membrane is a mosaic of components—primarily, phospholipids, cholesterol, and proteins— that move freely and fluidly in the plane of the membrane this fluidity means that if you insert a very fine needle into a cell, the membrane will simply part to flow around the needle; once the needle is removed, the membrane will flow back together seamlessly. 38 WSAqma_UKM  3) Internal Structure Cytoplasm Ribosomes Nuclear region/nucleoid Inclusions: Granules, vesicles/vacuoles Endospores WSAqma_UKM 39  Ribosomes Consist of ribonucleic acid and protein; serve as sites of protein synthesis Abundant in the cytoplasm of bacteria Often grouped in long chains called polyribosomes 70S in bacteria; 80S in eukaryotes Streptomycin & Erythromycin bind specifically to 70S ribosomes and disrupt bacterial protein synthesis WSAqma_UKM 40  Nuclear Region (Nucleoid) This centrally located nuclear region consists mainly of DNA, but also contains RNA and protein DNA: Usually one large, circular chromosome Vibrio cholerae: Two chromosomes, one large and one small Plasmids: Extrachromosomal pieces of smaller, circular DNA. Often, the genes carried in plasmids provide bacteria with genetic advantages, such as antibiotic resistance WSAqma_UKM 41 BACTERIAL NUCLEAR REGION Nuclear area not surrounded by a membrane (Murray 1968) WSAqma_UKM 42  Internal Membrane Systems Photosynthetic bacteria and cyanobacteria contain internal membrane systems Derived from the cell membrane and contain the photosynthetic pigments Nitrifying bacteria also have internal membranes WSAqma_UKM 43  Inclusions Within the bacterial cytoplasm are a variety of small bodies: 1. Granules: Not membrane bound and contain densely compacted substances (glycogen or polyphosphate) 2. Vesicles/vacuoles: Specialized membrane- enclosed structures that contain gas or poly- B-hydroxybutyrate (PHB) (lipid) WSAqma_UKM 44  Endospores A specialized resting structure found in bacteria such as Bacillus sp. and Clostridium sp. Helps the bacterial cell survive when conditions become unfavorable - protection Highly resistant to heat, drying, acids, bases, certain disinfectants and radiation WSAqma_UKM 45 Sporulation sporulation vegetative WSAqma_UKM 46 Endospore WSAqma_UKM 47  4) External Structure Flagella: -chemotaxis -phototaxis Axial filaments Pili: -conjugation pili and attachment pili Glycocalyx -capsule -Slime layer WSAqma_UKM 48  4) External Structure 1. Flagella: -chemotaxis -phototaxis 2. Pili: conjugation and attachment 3. Glycocalyx: -capsule -Slime layer WSAqma_UKM 49 Structures External to the Cell Wall -Short attachment pili (fimbriae) -Long conjugation pili (F-pili) Flagella: Fimbriae: Mostly made of flagellin. 1000’s of thin (~5 nm) & short Filament thick (20 nm) & long (10- appendages of helical proteins. 20 µm). Attachment to (specific) Filament possibly sheathed. surfaces, helps pathogenicity Varied locations on cell: Sex Pili/F pili: peritrichous monotrichous Conjugation; transfer of genetic material 1-10 slightly larger than fimbriae. Only in cells with a fertility plasmid (F factor), called donors. amphitrichous Facilitates genetic transfer lophotrichous between cells; with recipient gaining the F factor and possibly Atrichous: Bacteria without flagella other genes. Cocci shaped bacteria rarely have WSAqma_UKM flagella 50  PILI also involve in motility? Gliding motility: provides microbes to travel in environments with low water content, such as biofilms and soil WSAqma_UKM 51  Flagellum Polar, Monotrichous (Pseudomonas) Peritrichous (Salmonella) Polar, amphitrichous (Spirullum) Peritrichous (Proteus) Lophootrichous (Spirullum) WSAqma_UKM 52 G- G+ Bacterial flagellum Nine (9) pairs of outer microtubule Two (2) inner microtubule Eukaryotic WSAqma_UKM flagellum :Flagellum 9+2 53 Prokaryotic and Eukaryotic Flagella Protozoan, Tetrahymena Algae, WSAqma_UKM Euglena 54  Chemotaxis Sometimes bacteria move toward or away from substances in their environment by this nonrandom process Positive chemotaxis: net result is movement towards the attractant (nutrients) Negative chemotaxis: net result is movement away from the repellent WSAqma_UKM 55  Chemotaxis Hanging drop technique: to observe motility WSAqma_UKM 56  Phototaxis Move toward or away from light Positive phototaxis Negative phototaxis WSAqma_UKM 57  Axial filaments Spirochetes Also known as endoflagella WSAqma_UKM 58  Structures External to the Cell Wall Glycocalyx: S-layer (surface sugar coating; often layer): extremely well polysaccharide or polypeptide layer organized layer of external to the cell wall. protein subunits that 1. Capsules: organized, forms a rigid mesh, or consolidated, well mail, next to cell wall. attached. 2. Slime Layer: Functions in protection unorganized; loose; and in resisting removed easily. hypoosmotic stress Function in attachment; protection; virulence. WSAqma_UKM 59  Capsule Protective structure outside the cell wall of the organism that secretes it Only certain bacteria are capable of forming capsules (Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Klebsiella pneumoniae, Escherichia coli) Chemical composition of each capsule is unique to the strain of bacteria that secreted it Encapsulated bacteria are able to evade host defense mechanisms (phagocytosis)WSAqma_UKM 60 Capsule / glycocalyx (negative staining) WSAqma_UKM 61  Slime Layer Less tightly bound to the cell wall and is usually thinner than a capsule Protects the cell against drying, traps nutrients and binds cells together (biofilm) WSAqma_UKM 62 BACTERIAL LANGUAGE a smart phone, whatsapp, FB WSAqma_UKM 63  QUORUM SENSING the phenomenon whereby the accumulation of signalling molecules enable a single cell to sense the number of bacteria (cell density). WSAqma_UKM 64 autoinducer bacteria WSAqma_UKM 65  Quorum sensing Angler fish shiny little orb used to attract prey (and potentially mates). That glowing bulb is not actually part of the fish, it is a glowing colony of bacteria of the genus Photobacteria WSAqma_UKM 66  Quorum sensing The Hawaiian Bobtail Squid also uses a quorum sensing luminesent bacteria of the species Vibrio fishceri that allows the squid to camouflage into the starlight/moonlight at night. WSAqma_UKM 67 The bad Biofilms WSAqma_UKM 68