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Transcript
Structure of Prokaryotic & Eukaryotic Cells Review of Prokaryotic & Eukaryotic Cells • Nucleus vs nucleoid • DNA : circular vs linear, presence of histones • Membranous organelles • Cell wall-peptidoglycan • Cell division: binary vs mitosis • Ribosomes: 70S vs 80S • Cytoskeleton Shape • Cocci – Diplococci – Streptococci – Tetrads – Sarcinae – Staphylococci Bacillus • Coccobacilli • Diplobacilli • Streptobacilli Spiral • Vibrio-curved rods • Spirilla-helical & rigid • Spirochetes-helical & flexible • Other shapes • Pleomorphic Glycocalyx • • • • Glycolipids or glycoproteins Surrounds cell Capsule or slime layer Capsule more organized & attached to wall • Advantages of capsule Slime Layer(Biofilm) • • • • • Surrounds cell Loosely organized & not attached Tangled mass of fibers-dextran Attachment to surfaces -S. mutans Shields bacteria from immune defense & antibiotics Glycocalyx -Eukaryotes • • • • • Animal cells have one Made of carbohydrates No do not have a cell wall Surround plasma membrane Stabilizes PM Flagella • Movement – Spins like propeller – Clockwise or counter clockwise • Chemotaxis- movement toward or away Arrangements • • • • Monotrichous: one at end Amphitrichous: both ends Lophotrichous: tuft at end or ends Peritrichous: around the cell Structure • Composition-protein subunits: flagellin (H protein) E. coli H7 – Chains twisted together with hollow core – Helical shaped – Filament, hook, basal body – Hook – Basal body: Flagella • Basal body • Classified by flagella protein Axial Filament • Spirochetes – Treponema pallidum-syphilis – Borrelia burgdorferi-Lyme disease • Bundle of fibrials within a sheath • Corkscrew motion Movement Eukaryotes • Flagella & cilia – 9+2 arrangement of microtubules – Cilia in Paramecium & respiratory cells Prokaryote Fimbriae & Pili • Made of pilin: string of subunits • Function: attachment • Few to hundreds • Fimbrae • Pili-longer & fewer • Not in eukaryotes Cell Wall • Function • Basis of Gram stain Composition • Peptidoglycan – Repeating subunits of disaccharides • N-acetyl glucosamine (NAG) • N-acetyl muramic acid (NAM) • Linked alternately in rows – Attached by polypeptides • Tetrapeptide side chains link NAM subunits • Cross bridge of amino acids link tetrapeptides – Forms lattice Peptidoglycan • Confers shape & prevents lysis • Cell growth – Autolysins break cross linkages in peptidoglycan – Transpeptidases seal breaks – Penicillin inactivates these enzymes • Existing cells – Treat with lysozyme-tears, saliva etc. – Destroys linkages between carbohydrates Gram Positive Cell Wall • Thick layers: 40-80% of dry wt, up to 30 layers • Contains teichoic acid – Alcohol and phosphate – Negative charge – Cell growth-prevents lysis – Antigenic properties Gram Negative Cell Wall • Few layers of peptidoglycan- 10% • Outer membrane: bilayer • Periplasm LPS • Strong negative charge • Barrier to some antibiotics • Outer membrane-endotoxin – O polysaccharides – Lipid-lipid A Gram Stain • Differential stain dev by Hans Gram 1880s – Classifies bacteria into 2 groups – Based upon cell wall composition – Gram variable stain unevenly – Gram non reactive do not stain or stain poorly Comparison • Gram positives Gram Negatives • ETOH disrupts outer layer • CV-I complex is washed out of thin peptidoglycan layer • Counterstain Atypical Cell Walls • Streptococci • Mycobacteria • Mycoplasma – PM unique with sterols protect from lysis Mycoplasma • Lack a cell wall so pleomorphic • Classified with gram positives • Smallest genome of any bacteria • Droplet spread-use regular mask • Why can’t you use penicillin? Cell wall of Eukaryotes • • • • • Simpler than prokaryotes Algae & plants Fungi Yeasts Protozoa • Animals Plasma Membrane • Thin, fluid structure inside cell wall-viscous • Proteins • Phospholipids-2 layers Functions of Membrane • • • • • Selective permeability Passive transport: Active transport: Enzymes break down nutrients Infoldings Plasma Membrane of Eukaryotes • • • • Phospholipids and proteins Carbohydrates and sterols-cholesterol More rigid than prokaryotic PM Endocytosis • Exocytosis Cytoplasm of Prokaryotes • 80% water, thick, solutes • Increase in osmotic pressure on membrane – Rigid cell wall prevents lysis • Contains DNA • Ribosomes • Inclusion bodies Cytoplasm of Eukaryotes • Cytosol-fluid portion • Cytoskelton – Microfilaments: – Microtubules: – Intermediate filaments: • Cytoplasmic streaming Ribosomes • • • • 2 subunits of protein and rRNA 70s ribosomes Polyribosomes-chains Protein synthesis • Eukayotes-80s Inclusions • Polysaccharide granules • Sulfur granules • Reserve deposits-volutin (phosphates) Endospores • Unique to bacteria: Clostridium & Bacillus • Sporulation-formation of spores Germination • • • • Triggered by damage to coat Enzymes break down endospore Water enters & metabolism begins Not a reproductive structure Nuclear Area of Bacteria • Single, ds DNA chromosome • Attached to PM at some point • Nucleoid area, not a nucleus • Plasmids Nucleus • Largest structure in cell – Nucleoli • DNA associated with proteins -histones Organelles in Eukaryotes • Unique to eukaryotes • Membranous structures – Endoplasmic reticulum • Smooth & rough – Golgi complex – Lysosomes – Mitochondria – Cloroplasts ER • Flattened membranous sacs • Rough ER-ribosomes attached • Smooth ER- no ribosomes • Free ribosomes- proteins don’t need processing Golgi Complex • Stacks of membranous sacs • Receive transport vesicles from ER • Modify molecules to form glycoproteins, glycolipids lipoproteins • Transported in secretory vesicles to PM or to outside cell Lysosomes • Formed from Golgi – Contain digestive enzymes: proteases & nucleases – Break down old parts of cell – Breaks down pathogens Mitochondria • Double membrane • Generation of ATP Chloroplasts • Thylakoids-flattened membranous sacs • Contain DNA 70s ribosomes • Stroma thick fluid in center- Calvin cycle • Generation of ATP & sugars