Test Questions on Micro Bio – Microbiology – Flashcards
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Unlock answers· Prokaryotic cells |
o 0.2 – 3um in diameter o No membrane around genetic material or organelles o Examples § Bacteria § Archaea |
· Eukaryotic cells |
o 10-100um in diameter o Membrane bound nucleus and organelles o Complex cytoskeleton o Examples § Fungi § Protozoa § Algae § Helminths |
Size, shape, and arrangement of Prokaryotic cells
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o 3 basic shapes § Cocci (coccus, singular) – spherical/round § Bacilli (bacillus) – rod § Spiral – curved/twisted o Wide variety of shapes and sizes within each category § 0.2 – 3.0um in diameter § 0.5 – 10um in length § Cell arrangement depends on · How quickly divided cells separate · How many planes they divide in |
Cocci: Size, Shape and Arrangement |
o Cells round, ellipsoid, or bean shaped o Arrangement depends on species § One plane division – single cells, pairs, or chains (streptococci) § Two plane division – tetrads § Three perpendicular plane division – Groups of 8 (sarcinae) Random – bunches (staphylococci |
Bacilli: Size, Shape, and Arrangement |
o Individual cells can be § Short (coccobacilli) § Long § Thin § Fat § Filamentous o And can have ends that are § Square § Rounded § Ellipsoid § Spindle-shaped (fusiform) o Arrangement depends on species § Single cells § Pairs of cells § Chains o Corynebacterium – Form V, Y, and palisade (zigzaggy) shapes by a snapping division process o Actinomyces – form long branched filaments that can break up into rod and Y shapes o Mycoplasma – lack cell walls and are pleomorphic (variable shapes) |
Corynebacterium
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| Bacilli Example with form of V, Y, and palisade (zigzaggy) shapes by a snapping division process |
Actinomyces |
| Bacilli with form of long branched filaments that can break up into rod and Y shapes |
Mycoplasma |
| Bacilli that lack cell walls and are pleomorphic (variable shapes) |
· Spiral Bacteria: Size, Shape, and Arrangement |
o Three groups § Vibrios – Comma shaped rods § Spirilla – Rigid spiral shapes § Spirochetes – flexible corkscrews |
· External structures
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o Glycocalyx o Flagella o Fimbriae o Sex pili o Cell wall |
· Glycocalyx |
o Thick gelatinous polymer covering cell o Some don’t produce glycocalyx o Mostly polysaccharides, sometimes proteoglycans o Two types § Capsules – Thick, discrete, inseparable coat § Slime layer – Loosely formed around cell and separable o Coats are virulence factors § Interfere with phagocytosis § Prevent desiccation – enhances survival outside of host § Adhesins – allow to attach to inert surfaces § Initiate biofilms on implanted devices |
Catheter-Induced Infections
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o Staphylococci on skin attach to implanted catheters o Attachment triggers sticky slime layer production o Slime layer initiates biofilm which migrates into tissue o Most common infection acquired in hospitals – catheters need to be replaced every 2 days
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| Prosthetics |
o Artificial heart valves, hips, knees all subject to attachment by staphylococci o Attachment stimulates sticky slime layer and biofilm formation § Biofilms on artificial heart valves → infective endocarditis § Biofilms on artificial hips and knees → inflammation, bone resorption, failure. 25% chance another will be successful and the patient will walk |
· Biofilms on teeth |
o Bacteria on teeth form biofilms and ferment sugars to acids → caries o Also produce products causing gingival inflammation and periodontal disease
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· Capsular strain variation |
o Some pathogens have many different strains with chemically and antigenically different capsules o Variation affects host’s ability to develop immunity o Streptococcus pneumoniae – 90 distinct types o Antibodies are capsule-specific o After antibodies bind, phagocytes bind to antibodies (opsonization) and kill antigen o S. pneumoniae spontaneously form acapsular variants § Rough on media § Avirulent o Smooth are virulent |
· Prokaryotic Flagella
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o 3 Parts § Long filament § Hook (adaptor) § Basal body o 12-20nm diameter o Consist of flagellin protein monomers o Dissociate at pH 3 o Reassociate at pH 7 o Hook – attaches filament to basal body o Basal body – embedded in cell wall and turns like turbine § Proton motive force (H+ passing through channels and rotating) o Number of and location of flagella species specific and used in identification o 4 Arrangements § Monotrichous – Single § Lophotrichous – Two or more at one end § Amphitrichous – One of more flagella at each end § Peritrichous – Multiple flagella everwhere |
· Chemotaxis
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o Motile bacteria can move toward and away from stimulants (taxis) § Phototaxis – light is stimulant § Chemotaxis – chemical concentrations o Can change directions by reversing flagella rotation o Counterclockwise flagella rotation – straight line (run) while flagella wrap and rotate as one o Clockwise – flagella fly apart and cell tumbles o No chemoattractant – random o Chemoattractant present – cell moves up gradient § Higher gradient à more binding to receptors à longer runs § Lower gradient à less binding to receptors à more tumbling § Process: Run, tumble, run, tumble |
· Axial Filaments (Endoflagellum)
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o Convey motility to spirochetes o Fibrils at each end spiraling around under sheath à corkscrew motion |
Fimbriae
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o Fimbriae and pili used to be interchangeable and refer to nonmotile bristle-like structures o Sticky, non-motile, bristle-like filaments on surface o Thinner, straighter, shorter, more numerous than flagella (100-200 per cell) o Mediate attachment to surface, or other cells § Essential virulence factors due to adhesive properties o Adhesins – substances facilitating attachment § Glycocalyx – better for attachment to inert surfaces § Fimbriae – better for attachment to host cells and tissues o Fimbriae can be lectins § Bind to specific sugar of glycoprotein § Lectins agglutinate (clump) red blood cells § Specific sugar identified because when added, lectins do not agglutinate RBCs o Antigenic variation – ability to vary antigenic type of fimbriae § Allows pathogen to evade immune responses – new fimbrial antigen every 2 weeks § Hosts take 2 weeks to create antibodies – by that tame antigen factor changed § Example: Neisseria gonorrhoeae · Capable of hundreds of distinct fimbriae by recombining genes for protein subunit · Changes every 2 weeks · No immunity developed – 1 million new cases each year § Can also occur with flagella and other surface proteins
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Sex Pili
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o Long hollow tubular structures allowing Gram-negative bacteria to transfer DNA in conjugation o Like fishing rod (pole and hook) o Once other cell caught, disassembles cytoplasmic subunits and reels in cell till cell-cell contact o Pilus-positive cells (F+) produce only a few per cell o Made of self-aggregating protein monomer called pilin o Major mechanism for gram-negative genetic diversity o Facilitates transfer of antibiotic resistance o Gram-negative leading cause of nosocomial (hospital-acquired) infections § Often caused by bacteria with multiple genes for antibiotic resistance on plasmids from conjugation |
· Most prokaryotes have cell wall that provides
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o Shape
o Structure
o Protection against osmotic pressure
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Cell walls of bacteria and archaea different
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o Bacteria – Peptidoglycan,
o Archaea – No Peptidoglycan
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| Micoplasma |
| (bacteria) – Few with no cell wall |
· Bacteria cell walls |
o Gram-positive and Gram-negative both have peptidoglycan o Gram-positive § Single, thick, layer of peptidoglycan and other polymers § Adjacent and external to cytoplasmic membrane § See figure 3b-3 o Gram-negative 2 distinct layers § Outer membrane layer § Thin inner later of peptidoglycan § (Cytoplasmic membrane) § See figure 3b-4 |
| Peptidoglycan |
o Large, crosslinked polymer that maintains § Shape § Structural rigidity § Protection against osmotic lysis o Long polysaccharide chains § Crosslinked by peptide bridges § See Figure 3b-5 § Alternating ß-D-N-acetylglucosamine and ß-D-N-acetylmuramic acid residues connected ß (1-4) linkages with between acetylmuramic acid o Amino acids in peptide bridges vary by species but assembled from basic pentapeptide § L-alanine, D-isoglutamamide, L-lysine, D-alanine, D-alanine § Contains D-alanine and D-isoglutamamide § Diamino in pos 3 can be lysine, ornithine, or diaminopimelic o Terminal D-alanine lost in transpeptidation of adjacent side chains (at acetylmuramic acid) § Link between Carboxyl at 4th peptide (D-alanine) and side chain amino group of 3rd peptide on adjacent chain § Some gram-positive have extra amino acids in crosslink (interbridge) § Degree of crosslinking varies by species · Staph aureus – 100% · Escherichia coli – 70% o Peptidoglycan AKA murein o Ideal target for antibiotics since only found in bacteria |
Peptidoglycan and Antibiotics |
o Peptidoglycan disruption antibiotics harmless to eukaryotes o Antibiotics interfering with peptidoglycan synthesis § Examples · Penicillin · Cephalosporins · Vancomycin § Inhibit crosslinking à defective walls à lyse in hypotonic solutions |
Enzymatic breakdown of peptidoglycan |
o Hydrolyzed by § Lysozyme – hydrolyzes N-Ac-Mur-ß-(1,4)-N-Ac-Glc bond § Endopeptidases – hydrolyze peptide bridges (crosslinks) § Amidases – hydrolyze linkage between N-Ac-muramic acid and L-alanine o Lysozyme can be used to prepare § Protoplasts – cell wall-less gram-positive § Spheroplasts – cell wall-less gram-negative § Both must be kept in isotonic solutions or lysis occurs
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· Lysozyme |
o Present in most human tissues § Degrades peptidoglycan causing bacteria to lyse § Used by phagocytes o Some gram-positive mutate to be lysozyme resistant by either § OH groups on muramic acid § Removing N-acetyl group from N-Ac-glucosamine |
Gram-positive walls
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o Single thick layer of peptidoglycan o Strong, but porous to chemicals <1000 daltons o 30 murein chains thick o 50-90% of cell dry weight o Include proteins, polysaccharides, and/or lipids § Covalently attached to peptidoglycan or anchored in cytoplasmic membrane § Pass through cell wall and stick out o All have polysaccharide polymer called teichoic or similar teichuronic acid |
Teichoic acids
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o Only in gram-positive o Essential o Function unknown but may regulate cell separation or store metal ions and sugars o Long, linear (ribitol-phosphate)n or (glycerol-phosphate)n (n=20-30) polymers § Hydroxyl groups of sugars often replaced with D-alanine or a sugar o Ribitol teichoic acids—wall teichoic acids § Covalently linked to OH group on C-6 of N-ac-muramic acid o Glycerol teichoic acids – lipoteichoic acids § Covalently linked to glycolipid in cytoplasmic membrane |
Teichuronic acids
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Phosphate deficiency in medium à acidic sugars like glucouronic acid substitute for phosphate. May regulate cell separation at growth or serve as storage polymers for metal ions and sugars |
Resistance to degradation of gram-positive bacteria |
o Group A streptococcus covered with M-protein à not easily degraded § Intravenous injection à inflammation, arthritis, and rheumatoid nodules o Mycobacterium tuberculosis has outer layer of arabinogalactan and waxy lipids called mycolates à resistant to macrophages § Causes tuberculosis when poor cellular immunity |
· Gram-Negative Cell Walls
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o Two distinct layers § Outer membrane layer composed of · Lipopolysaccharide · Proteins · Phospholipids § Inner layer · Thin layer of peptidoglycan · Few saccharide chains in thickness · Not fully cross-linked o Cytoplasmic membrane internal and adjacent to peptidoglycan layer o Space between membranes called periplasmic space o Anchor lipoprotein § Helical § Small (7500 daltons) § Covalently attached to one of every 10 tetrapeptide units · Between carboxyl terminus of lipoprotein and side amino group of diamino acid at pos 3 in tetrapeptide unit § Lipid portion embedded in inner leaf of outer membrane § Anchors inner and outer layers of cell wall o Less peptidoglycan à less rigid and strong than gram-positive |
Lipopolysaccharide (LPS) Structure |
o Unique, complex glycolipids with three covalently linked parts § Lipid A § Core polysaccharide § O-specific polysaccharide chain or O-antigen o Lipid A and core polysaccharide similar in all gram-negatives o O-antigen different for each gram-negative species |
Lipid A
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o Large, complex, unusual glycolipid o Embedded in outer leaf of outer membrane of gram negative bacteria o Large size and numerous saturated fatty acids make outer membrane more rigid than normal |
· Core polysaccharide
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o Links lipid A to O-specific polysaccharide o Contains § 8 carbon sugar – 2-keto-3-deoxyoctulosonic acid (KDO) § 7 carbon sugar – L-glycero-D-mannoheptose § Other sugars o General structure § [KDO-Heptose-Other sugars] o Mutants lacking § KDO à can’t grow § Seven carbon sugarà functional deficiencies but survive § Other sugars à form atypical rough ® colonies instead of smooth, but normal |
| O-Specific Polysaccharide Chain |
o Long polymer extending out from membrane o Attached to terminal sugar of core polysaccharide o 3-5 sugars repeating 10-50 times o Contains unusual sugars § Dideoxyhexoses § Aminohexuronic acids § Deoxyaminohexoses o Major surface antigen of gram-negative bacteria o Different for each species and even strains o Called O-specific antigen or O-antigen o Variation of Salmonella typhurium § 2000 strains each with different O-antigen § Immunity only develops to specific strain § Can get over and over, and vaccine impossible |
Lipopolysaccharides
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o LPS highly toxic to mammals AKA endotoxins o Lipid A moiety is toxic component o Signs and symptoms § Sublethal - <100ug à Fever, edema, low blood pressure and aches and pains § Lethal - >100ug àFever, edema, low blood pressure, shock, intravascular coagulation, loss of consciousness, circulatory collapse, organ failure and death within hours of first symptoms o Endotoxin poisoning happens when gram-negative bacteria enter bloodstream and multiply – septicemia § Release endotoxins from cell wall as they grow § 80,000 cases of gram-negative septicemia each year in US § Difficult to treat § High fatality (25%) even in hospital § Antibiotics sometimes exacerbates by causing lysis and endotoxin release o Also concern in pharmaceutical § Pyrogens – cause fever § Trace amounts even 1 nanogram injection of endotoxin causes fever § Most things are cominated with trace endotoxins because gram-negative bacteria are everywhere § Even if sterile, need to be tested for pyrogens § Autoclaving doesn’t destroy endotoxins § Must be filtered or distilled § Horseshoe crab (limulus lysate) tests for endotoxins by clotting in presence of trace amounts § Or inject in rabbit and measure fever
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Proteins and phospholipids in Gram-Negative Cell Walls |
o Inner leaf of outer membrane mainly phospholipids o Proteins § Major component – Porin, a channel forming protein allowing small nutrients to pass § Lipoprotein – attached to every 10 tetrapeptides in peptidoglycan and anchoring layers of cell wall § Periplasmic space and Cytoplasmic membrane contain other nutrient transport proteins |
Practical Consequences of Gram-Negative Cell Walls
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o LPS is large and solid § Makes outer membrane rigid and not easily penetrated by hydrophobic compounds § Resistant to detergents since they cannot penetrate o Porin makes outer membrane permeable to small hydrophilic compounds <600 daltons § Resistant to many antibiotics and inhibitory dyes due to being too large for porin o More susceptible to osmotic lysis due to thinner peptidoglycan wall |
Proteins and phospholipids in Gram-Positive Cell Walls
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o Small molecules <1000 daltons can penetrate through porous cell wall o Sensitive to many antibiotics and inhibitory dyes |
Bacteria without cell walls |
o Mycoplasma is a genus of bacteria without cell walls o L forms are laboratory produces mutant bacteria without cell walls |
· Archaea Cell Walls |
o Not well characterized o Polysaccharides and proteins but no peptidoglycan o Cell wall polymer – pseudomeurein o Some stain gram-positive, some gram-negative |
· Cytoplasmic membrane
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o Prokaryotes contain proteins Eukaryotes glycoproteins A selectively premeability barrier
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· Membrane lipids
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o Phosphoglycerides o Sphingolipids o Sterols |
· Phosphoglycerides
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o Amphipathic lipid w/ § Glycerol core § Two long hydrocarbon chain tails § Hydrophilic alcohol head o Most common lipid in membranes o Structurally heterogenous o Fatty acyl chains connect to OH of phosphoglycerol via ester linkages o Alcohol attaches to PO4 group o Variety of alcohol and fatty acyl chains § Most common alcohols · Ethanolamine · Choline · Serine · Inositol · Glycerol § Most common fatty acyl chains · 16 & 18 carbon saturated, mono-unsaturated, and di-unsaturated o Plasmalogens – One fatty acyl by ester, one by ether o Phosphoglycerol diethers – Both fatty acyls by ether o Diphosphoglycerol tetraethers – Glycerol at both ends via ether linkages o Phosphoglycerol diethers and diphosphoglycerol tetraethers found in archaea |
Sphingolipids |
o Amphipathic lipids derived from sphingosine (amino alcohol with long hydrocarbon tail o Only found in eukaryotic cells o Sphingomyelin – phosphocholine attached to sphingosine’s terminal hydroxyl group, and a fatty acid to its amino group o Glycosphingolipids – one or more sugar to sphingosines terminal OH group and fatty acid to amino group o 2 – 10 % of lipids in eukaryotic cell membranes and localize in lipid rafts |
Sterols
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o Rigid 4 ring hydrocarbon compounds o Constitute 25% of lipids in eukaryotic cell plasma membranes o Variety in membranes § Animals – cholesterol § Fungi – Ergosterol § Plant – Stigmasterol o Bacteria (except Mycoplasma) and archaea don’t have sterols in plasma membrane § Some have hopanoids in membrane, sterol like lipid |
Structure of Biological membrane |
o Lipid bilayer o Embedded proteins o Each layer – leaflet o Basic components § Phosphoglycerides § Sphingolipids o Auto aggregate tail to tail o Diphosphoglycerol tetraethers à very stable lipid monolayer found in extreme thermophile archaea
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Physical Properties of Biological Membranes
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o Under physiological conditions · Low viscosity fluid state like light oil · Lipids move laterally but cannot change leaflets · Fluid mosaic model o Membrane fluidity varied by lipid composition § Cells can vary saturated versus unsaturated fatty acyl chains · Lower temp more unsaturated · Higher temp more saturated o Eukaryotes can add sterols § Make membrane more rigid at high temps § Keep sphingolipids and phospholipids from packing too tightly at lower temps |
· Membrane proteins |
o 18% to 76% of membranes by weight § Prokaryotes cytoplasmic membrane – 70% protein and 30% lipids § Eukaryotes cytoplasmic membrane – 50% protein 50% lipids o Some proteins span membrane, others in one leaflet o Move laterally but not from leaflet o Functions § Transporters § Anchors § Receptors § Enzymes § Adhesins § Signalling § Recognition |
Differences in cell membranes |
o Bacteria, archaea, and eukaryotes use different lipids in forming cytoplasmic membranes o Bacteria § Most simple phosphoglycerides only § Sphingolipids and sterols only added in Mycoplasma § Some bacteria have hopanoids – sterol like lipids o Archaea § Phosphoglycerol diethers or diphosphoglycerol tetraethers with branched hydrocarbon side chains § Branched hydrocarbon chains from 5 carbon monomer isoprene § Phosphoglycerol dietheres work like phosphoglycerides but ether more resistant to hydrolysis than esters § Diphosphoglycerol tetraethers – phosphoglycerol to each end of 2 long branched hydrocarbon chains (often 40 carbon diphantyl) via ether linkages · Extreme thermophiles · Lipid monolayer o Eukaryotes § Phosphoglycerides § Sphingolipids § Sterolds o Prokaryotic membranes perform much function of eukaryotic organelles and have proteins for § Aerobes and facultatively anaerobic bacteria contain – respiratory electron transport chain § Photosynthetic bacteria – photosynthetic enzymes § Cell division § Cell wall precursor synthesis o Membrane folds back on itself in invaginations called mesosomes § Could contain ETC § Could be artifact o Cytoplasmic membranes destroyed by § Alcohols § Quaternary ammonium compounds § Detergents § Antibiotics called polymyxin |
Nutrient transport across membrane
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o Pure phospholipid impermeable to hydrophilic compounds but they need them to live § Overcome by transport proteins § Makes chemical gradients possible o Concentration gradient – chemical inequality o Charge gradient – charge inequality § 70mV across cytoplasmic membrane § Cytoplasm contains large negatively charged molecules (proteins, nucleic acids) · Cannot escape · Need to be counterbalanced by positive charges in cell · Do so with high K+ concentration in cells · Sodium potassium pump o Uses ATP to pump K+ in and Na+ out o Membrane freely permeable to K+ but not Na+ o High concentration inside vs out (140mM/4mM) causes K+ to sneak out, leaving – charge inside o – charges on inside attract + charges outside § Oppose K+ leaking out o Eventually K+ attracted to negative charge inside o K+ leaks until electrical gradient force equals chemical gradient force o -70mV o Called Electrochemical gradient § Used to transport substances across membrane o Certain drugs (digitalis) inhibit Na K pump and lessen gradient à contractions come easier and more forcibly. usead to treat congestive heart failure § Foxglove naturally does this – medicine and poison |
Group transport – Active transport process
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o Only in prokaryotes o Substrate gradient created by phosphorylating substance being brought into cell o Phosphorylated form unable to cross back o Phosphoenolpyruvate-sugar phosphotransferase system (PEP-PTS) § Transports sugar into cells § Membrane bound proteins transfer phosphate from PEP to sugars transported into cell § Internal sugars not affected § Highly efficient and rapid system used to take up sugar § Effective at low sugar concentrations such as 1 ppm § Dental plaque use PEP-PTS to take up sugars in oral cavity · Only fed several times a day · Have to take up sugar rapidly · Figure 3c-45 shows one tooth bathed in sugar solution and stained or sugar to see how plaque uptakes sugar · Microscopic observation shows new polysaccharies inside bacteria (especially streptococci) · Virulence factor for denatl caries because it allows acid production for prolonged periods of time.
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Prokaryotic Non-Membranous Organelles
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o Cytoskeleton § Network of protein fibers in cytoplasm § Some prokaryotes don’t have one, some have simple § Cocci do not have it § Rod and spiral shaped cells usually have cytoskeleton of actin-like protein § Eukaryotes have complex cytoskeleton o Ribosome § Large non-membranous organelles that synthesize proteins § Thousands in one prokaryote § Size in svedberg (S) units – rate of sedimentation in centrifuge § Prokaryotes – 70 S (smaller)He said know these 70s and 80s numbers and what they mean § Eukaryotes – 80 S (larger) § Subunits · 30 S and 50 S · each contains proteins and rRNA |
Prokaryotic Inclusion Bodies |
o Large granules or storage deposits in cytoplasm o Variety of purpose eg. Energy reserve § Glycogen § Starch § Sulfur granules § Gas vacuoles o Gas vacuoles allow to float where light reaches |
Bacterial endospores
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o Highly resilient resting structures to survive adverse conditions o Resistant to killing by chemical and physical agents than normally sterilize § Not killed by heating or boiling § Need 121 degrees C moist heat at 15 PSI for 15 min (autoclave or pressure cooker) o Resistant to staining – have to be stained while heated and have a detergent o Resilience § Little to no water or cytoplasm § Multiple layers of dipicolinic acid – calcium chelator only in bacterial endospores o Virulence factor for endospore forming pathogens § Bacillus anthracis à anthrax · Viable in soil for centuries · Slaughtering and burn carcasses, quarantine land, wait till not infective |
Endospore formation |
o Sporulation o See Figure 3c – 55 (He said he does not ask detaqils about this) § DNA divides and aligns along cell axis § Membrane invaginates and forms forespore § Forespore covered in another cytoplasmic membrane, other DNA degrades § Cortex of calcium and dipicolinic acid deposited between membranes § Spore coat forms § Endospore matures by unknown process (increases resistance) § Released from cell o Takes 4-8 hrs to form o One cell à one endospore (KNOW) and that it is not a reproductive mechanism o Formed within cell o Depending on species can form centrally, subterminally (near one end), or terminally (at one end) § Identifying trait for species o Appropriate conditions à endospore grows AKA germination § Form single cell § Germination triggered by sugar, amino acid, or other nutrient o Bacillus and Clostridium only medical important genre endospore forming bacteria § Clostridium forms potent exotoxins and cause · Tetanus · Botulism · Gas gangrene § Bacillus · Anthrax · Food poisoning § Widely distributed in nature · Common in soil, plants, decaying vegetation, and intestines § Common contaminants of wounds · Germinate in wounds and cause gas gangrene, tetanus, and anthrax § Common contaminants of vegetables and meat · Germinate in fresh and canned foods and cause food spoilage and gastroenteritis or botulism o Killing of endospore contaminants major concern to food industry, health care professionals, and government regulators § Medical and food prep operations must use sterilization processes known to kill endospores § States require monitoring of sterilization method effectiveness § PA Dept of Environmental Resources require biweekly testing of sterilization devices for med and dental instruments with biological indicator § OSHA, CDC, and ADA all recommend weekly testing with biological indicator
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Glycocalyx
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Eukaryotic external structure Eukaryotes without a cell well produce protective glycocalyx – glycoproteins covering plasma membrane
§ Animal and protozoan cells produce glycocalyx § Fungi, algae, and plant cells have cell walls and not glycocalyx § Functions · Protect from outside environment · Hold cells together · Strengthen surface · Protect against dehydration, microbes, injury · Participate in cell-cell communication and recognition § Glycocalyx of protozoa is called pellicle |
Cell Walls |
§ Fungi, algae, plant cells have cell walls, animal and protozoan cells don’t § Composed of polysaccharides, not peptidoglycan · Plants – cellulose · Fungi – mostly chitin, some cellulose · Yeasts – glucans and mannans · Algae - -cellulose and other polymers depending on species (agar, carrageenan, silicates, algin, calcium carbonate)
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Flagella
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Eukaryotic external structure § Structurally different than prokaryotic flagella · Eukaryotes - Long cytoplasmic projections composed of microtubules and covered by cell membrane · Prokaryotes – long extracellular filaments § Microtubules · 9 + 2 – 9 doublets around 2 single · Basal body – 9 + 0 (centriole) § Single or multiple, often at end of cell § Movement · Eukaryotes – wave or whip-like motion pulls or pushes it forward · Prokaryotes – rotate |
Cilia |
§ Hairlike structures shorter than flagella § Could be hundreds § Cell-membrane bound cytoplasmic projections § 9+2 over 9+0 basal body § Whip like motion and beat rhythmically § Propels cell or moves nutrients |
Cell membrane
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o Phospholipid bilayer containing § Sterols – more rigid at higher temps and more fluid at lower by preventing packing § Glycoproteins · Recognition molecules · Enzymes · Receptors · Signaling molecules · Channels · Transporters · Anchors o Prokaryotes § Lack sterols (except mycoplasma) § Have proteins not glycoproteins o Permeability barrier o Nutrient transport § Same passive and active transport as prokaryotes § Endocytosis · Phagocytosis · Pinocytosis · Receptor-mediated endocytosis · Exocytosis § Prokaryotes don’t carry out endo/exocytosis o Phagocytosis § Ingestion of particulate materials by cell § Pseudopods extend around object, fuse together, form phagosome § Lysozome fuses with and forms phagolysosome o Endocytosis § Pinocytosis – ingestion of liquid materials by cell · Pseudopods extend and capture liquid in vesicle § Receptor-mediated endocytosis – pinocytosis involving receptor bound molecules · Same process – receptors inside vesicle o Exocytosis § Reversal of endocytosis |
· Eukaryotic Cytoplasm
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o Everything inside plasma membrane not in nucleus o More complex than prokaryotic § Water § Inorganic and organic molecules § Non-membranous organelles § Membrane-bound organelles § Complex cytoskeleton o Cytoplasm streaming – movement not found in prokaryotes |
Eukaryotic Non-Membranous Organelles |
o Ribosomes § 80S – 60S and 40S § Larger than 70S prokaryotic § Many antibiotics specific for prokaryotic ribosomes § Can attach to ER and sends products into ER to be packaged o Centrioles and centrosome § Animal and fungal cells have two microtubule structures – centrioles · Right angles · Form centrosome · Participate in mitosis and cytokinesis in animal cells · 9+0 arrangement o Proteosomes § Degrade senescent, improperly folded, damaged, and or foreign proteins into peptides · Exposed cysteines in proteins bind to sulfhydryl protein ubiquitin · Ubiquitin-tagged proteins transported to proteosomes § Form epitopes bound to MHC on cell surface and presented to T cells for immune response |
Eukaryotic Vesicles and Vacuoles
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o Small – vesicles, used for transport
o Large – vacuoles, used for storage
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· Lysosome
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o Vesicles with hydrolytic enzymes o Digest endocytosed food, microbes, etc o Inactive at neutral pH but active at pH 5 or lower o Proton pumps in membrane lower pH of phagolysosomes |
· Peroxisomes
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o Membrane bound organelles with enzymes to decompose poisonous metabolic wastes o Rich in catalase – destroys H2O2 o Rich in Peroxidases – destroy superoxide anion O2-, free radicals, and degrade fatty acids o Numerous in kidney and liver cells |
· Mitochondria |
o Double membrane structures that carry out Krebs and oxidative phosphorylation § Inner membrane folded into cristae § Cristae contain ETC and are where oxidative phosphorylation happens o Contain § Circular DNA § 70 S ribosomes § Replicate themselves |
· Chloroplasts
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o Double membrane structures in photosynthetic cells (algae and plants) that convert light into ATP and CO2 into sugars § Light harvesting chemicals are pigments in membranous sacs thylakoids § Fluid between thylakoids and inner membrane called Stroma § Prokaryotes that have light harvesting pigments and photosynthetic enzymes have them in · Folds of plasma membrane called photosynthetic lamellae § Circular DNA § 70 S ribosomes § Self replicating |
Endosymbiotic theory
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o Mitochondria from small aerobic bacteria ingested § Became internal parasite à symbiotic relationship § Retained portion of DNA but lost ability to exist independently § Eukaryotic cell also dependent o Similar theory for chloroplasts
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| Plasmids |
Small circular extra chromosomal DNA in prokayotes. Convey antibiotic resistance or virulence factors and spread antibiotic resistense gens to microbes the lack them. readily transfered form one prokaryote to another. |
| Proteosomes |
protein organelles in cytoplasm of animal cells that degrade senscent, improperly folded, damaged and/or foreign proteins in cytoplasm. ubiquitin, a small sulhydryl protein in cytoplasm, which proteosomes with exposed cysteine residues bind to exposed sulhydrl group. Play key role in adaptive iummune response by produceing foreign (non self) peptides |
