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Structure of Prokaryotic & Eukaryotic Cells

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

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Structure of Prokaryotic & Eukaryotic Cells

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  1. Structure of Prokaryotic & Eukaryotic Cells

  2. 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

  3. Shape • Cocci • Diplococci • Streptococci • Tetrads • Sarcinae • Staphylococci

  4. Bacillus • Coccobacilli • Diplobacilli • Streptobacilli

  5. Spiral • Vibrio-curved rods • Spirilla-helical & rigid • Spirochetes-helical & flexible • Other shapes • Pleomorphic

  6. Glycocalyx • Glycolipids or glycoproteins • Surrounds cell • Capsule or slime layer • Capsule more organized & attached to wall • Advantages of capsule

  7. 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

  8. Glycocalyx -Eukaryotes • Animal cells have one • Made of carbohydrates • No do not have a cell wall • Surround plasma membrane • Stabilizes PM

  9. Flagella • Movement • Spins like propeller • Clockwise or counter clockwise • Chemotaxis- movement toward or away

  10. Arrangements • Monotrichous: one at end • Amphitrichous: both ends • Lophotrichous: tuft at end or ends • Peritrichous: around the cell

  11. 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:

  12. Flagella • Basal body • Classified by flagella protein

  13. Axial Filament • Spirochetes • Treponema pallidum-syphilis • Borrelia burgdorferi-Lyme disease • Bundle of fibrials within a sheath • Corkscrew motion

  14. Movement Eukaryotes • Flagella & cilia • 9+2 arrangement of microtubules • Cilia in Paramecium & respiratory cells

  15. Prokaryote Fimbriae & Pili • Made of pilin: string of subunits • Function: attachment • Few to hundreds • Fimbrae • Pili-longer & fewer • Not in eukaryotes

  16. Cell Wall • Function • Basis of Gram stain

  17. 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

  18. 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

  19. 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

  20. Gram Negative Cell Wall • Few layers of peptidoglycan- 10% • Outer membrane: bilayer • Periplasm

  21. LPS • Strong negative charge • Barrier to some antibiotics • Outer membrane-endotoxin • O polysaccharides • Lipid-lipid A

  22. 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

  23. Comparison • Gram positives

  24. Gram Negatives • ETOH disrupts outer layer • CV-I complex is washed out of thin peptidoglycan layer • Counterstain

  25. Atypical Cell Walls • Streptococci • Mycobacteria • Mycoplasma • PM unique with sterols protect from lysis

  26. 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?

  27. Cell wall of Eukaryotes • Simpler than prokaryotes • Algae & plants • Fungi • Yeasts • Protozoa • Animals

  28. Plasma Membrane • Thin, fluid structure inside cell wall-viscous • Proteins • Phospholipids-2 layers

  29. Functions of Membrane • Selective permeability • Passive transport: • Active transport: • Enzymes break down nutrients • Infoldings

  30. Plasma Membrane of Eukaryotes • Phospholipids and proteins • Carbohydrates and sterols-cholesterol • More rigid than prokaryotic PM • Endocytosis • Exocytosis

  31. Cytoplasm of Prokaryotes • 80% water, thick, solutes • Increase in osmotic pressure on membrane • Rigid cell wall prevents lysis • Contains DNA • Ribosomes • Inclusion bodies

  32. Cytoplasm of Eukaryotes • Cytosol-fluid portion • Cytoskelton • Microfilaments: • Microtubules: • Intermediate filaments: • Cytoplasmic streaming

  33. Ribosomes • 2 subunits of protein and rRNA • 70s ribosomes • Polyribosomes-chains • Protein synthesis • Eukayotes-80s

  34. Inclusions • Polysaccharide granules • Sulfur granules • Reserve deposits-volutin (phosphates)

  35. Endospores • Unique to bacteria: Clostridium & Bacillus • Sporulation-formation of spores

  36. Germination • Triggered by damage to coat • Enzymes break down endospore • Water enters & metabolism begins • Not a reproductive structure

  37. Nuclear Area of Bacteria • Single, ds DNA chromosome • Attached to PM at some point • Nucleoid area, not a nucleus • Plasmids

  38. Nucleus • Largest structure in cell • Nucleoli • DNA associated with proteins -histones

  39. Organelles in Eukaryotes • Unique to eukaryotes • Membranous structures • Endoplasmic reticulum • Smooth & rough • Golgi complex • Lysosomes • Mitochondria • Cloroplasts

  40. ER • Flattened membranous sacs • Rough ER-ribosomes attached • Smooth ER- no ribosomes • Free ribosomes- proteins don’t need processing

  41. 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

  42. Lysosomes • Formed from Golgi • Contain digestive enzymes: proteases & nucleases • Break down old parts of cell • Breaks down pathogens

  43. Mitochondria • Double membrane • Generation of ATP

  44. Chloroplasts • Thylakoids-flattened membranous sacs • Contain DNA 70s ribosomes • Stroma thick fluid in center- Calvin cycle • Generation of ATP & sugars

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