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The Cell Theory

The Cell Theory. All organisms are composed of one or more cells. Cells are the smallest living things, the basic units of organization of all organisms. Cells only arise by division of a previously existing cell. Why Are Cells So Small?. It’s all about: Surface Area-to-Volume Ratio.

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The Cell Theory

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  1. The Cell Theory • All organisms are composed of one or more cells. • Cells are the smallest living things, the basic units of organization of all organisms. • Cells only arise by division of a previously existing cell.

  2. Why Are Cells So Small? It’s all about:Surface Area-to-Volume Ratio Size Matters! Large Cells vs. Small Cells Cell radius (r) 1 unit 10 units Surface area (4╥r2) 12.57 units2 1257 units2 Volume (4/3╥r3) 4.189 units3 4189 units3 ______ ______ SA/V= 2.98 0.30 As a cell get larger, its volume increases at a faster rate than its surface area!

  3. Eukaryote Prokaryote Archaebacteria&Bacteria Classification • Old 5 Kingdom system • Monera, Protists, Plants, Fungi, Animals • New 3 Domain system • reflects a greater understanding of evolution & molecular evidence • Prokaryote: Bacteria • Prokaryote: Archaebacteria • Eukaryotes • Protists • Plants • Fungi • Animals

  4. KingdomBacteria KingdomArchaebacteria KingdomProtist KingdomFungi KingdomPlant KingdomAnimal

  5. Domain Bacteria Domain Archaea Domain Eukarya Common ancestor Prokaryotes Domain Bacteria Domain Archaebacteria

  6. Bacteria live EVERYWHERE! • Bacteria live in all ecosystems • on plants & animals • in plants & animals • in the soil • in depths of the oceans • in extreme cold • in extreme hot • in extreme salt • on the living • on the dead Microbes alwaysfind a way tomake a living!

  7. Bacterial diversity rods and spheres and spirals… Oh My!

  8. eukaryote cell prokaryotecell Prokaryote Structure • Unicellular • bacilli, cocci, spirilli • Size • 1/10 size of eukaryote cell • 1 micron (1um) • Internal structure • no internal compartments • no membrane-bound organelles • only ribosomes • circular chromosome, naked DNA • not wrapped around proteins

  9. Domain Bacteria Domain Archaea Domain Eukarya Common ancestor Eukaryotes Domain Eukarya

  10. eukaryote cell prokaryotecell Eukaryote Structure • Unicellular or Multicellular • Plant, animal, fungi, protist • Size • 10X larger than a prokaryote cell • 10-100 micron (1um) • Internal structure • Far more complex (compartmentalized) • nucleus containing DNA • other membrane-bound organelles • ribosomes (no membrane) • Linear chromosome • wrapped around proteins

  11. Prokaryote vs. Eukaryote Chromosome Prokaryote Eukaryote double helix

  12. mitochondria chloroplast Variations in Cell Interior cyanobacterium(photosythetic) bacterium aerobic bacterium internal membranesfor respirationlike a mitochondrion(cristae) internal membranesfor photosynthesislike a chloroplast(thylakoids)

  13. outer membrane of lipopolysaccharides Gram-negative bacteria Gram-positive bacteria peptide side chains outer membrane cell wall peptidoglycan cell wall peptidoglycan plasma membrane plasma membrane protein Prokaryote Cell Wall Structure That’simportant foryour doctorto know! peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides

  14. Prokaryotic metabolism • How do bacteria acquire their energy & nutrients? • photoautotrophs • photosynthetic bacteria • chemoautotrophs • oxidize inorganic compounds • nitrogen, sulfur, hydrogen… • heterotrophs • live on plant & animal matter • decomposers & pathogens

  15. Genetic variation in bacteria • Mutations • bacteria can reproduce every 20 minutes • binary fission • error rate in copying DNA • 1 in every 200 bacteria has a mutation • you have billions of E. coli in your gut! • lots of mutation potential! • Genetic recombination • bacteria swap genes • plasmids • small supplemental circles of DNA • conjugation • direct transfer of DNA conjugation

  16. Bacteria as pathogens • Disease-causing microbes • plant diseases • wilts, fruit rot, blights • animal diseases • tooth decay, ulcers • anthrax, botulism • plague, leprosy, “flesh-eating” disease • STDs: gonorrhea, chlamydia • typhoid, cholera • TB, pneumonia • lyme disease

  17. Bacteria as beneficial (& necessary) • Life on Earth is dependent on bacteria • decomposers • recycling of nutrients from dead to living • nitrogen fixation • only organisms that can fix N from atmosphere • needed for synthesis of proteins & nucleic acids • plant root nodules • help in digestion (E. coli) • digest cellulose for herbivores • cellulase enzyme • produce vitamins K & B12 for humans • produce foods & medicines • from yogurt to insulin

  18. Got any Questions?? Ask da’ Boss!

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