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CLASSIFICATION OF CELLS

CLASSIFICATION OF CELLS. Lecture 2. What is exactly is life?. From the Biological perspective- Life is described with ALL the following 4 properties (at this time) CELLULAR : Firstly, every living thing is cellular

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CLASSIFICATION OF CELLS

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  1. CLASSIFICATION OF CELLS Lecture 2

  2. What is exactly is life? • From the Biological perspective- Life is described with ALL the following 4 properties (at this time) • CELLULAR: Firstly, every living thing is cellular • it is either a single-celled creature (unicellular - bacterium, brewers yeast, amoeba) • or a creature composed of many cells (muticellular - toadstool, frog, plant, man) • PROPERGATE: Living things reproduce themselves • Either individually (asexual reproduction) • In sexual pairs (sexual reproduction • METABOLIZE: Life uses processes collectively called metabolism to convert materials and energy for its needs • EVOLUTION: Life undergoes evolution to different forms

  3. LIFE • There is no hard and fast definition of life! • Scientists are manipulating life at this time! • New life is being created in test tubes! • NASA is looking for new life forms at this time • Was McCoy right when he found silicon based life-forms?

  4. What is living? • Animals • Plants • Fungi • Bacteria • Viruses • Prions • Atoms

  5. What is living? • Animals - yes • Plants - yes • Fungi - yes • Bacteria - yes • VIRUSES - no • PRIONS - no • ATOMS - no

  6. Classification of cells • Two main classes of cells - so far! • Nucleus - Do they have or not have? • Prokaryotic cells - All Bacteria & Archaea - no nucleus • Eukaryotic cells - Plants, animals, fungi, and protists - all have a nucleus • Prokaryotes also lack organelles or cytoskeleton • Otherwise, they function very much the same.

  7. PROPERTY Nucleus Cell Diameter Cytoskeleton Organelles DNA content (bp) Chromosomes Eucaryotes Present 10 - 100 um Present Present 1.5x10E7 to 5x10E9 Multiple linear DNA molecules Prokaryotes vs. Eukaryotes Procaryotes • Absent • 1 um • Absent • Absent • 1x10E6 to 5x10E6 • Single circular DNA molecule

  8. KNOW YOUR SI UNITS • Each student of science must be at ease with the SI unit scale • Length metre: m (the correct English spelling of the unit is "metre", but the variant "meter" is frequently used in the United States) • Mass kilogram: kg Time second: s • electric current ampere: A thermodynamic temperature kelvin: K • SI Prefixesexponent (base 10) of decimal numbers: E n = 10nFactor • 109 E 9 giga G • 106 E 6 mega M • 103 E 3 kilo k • 102 E 2 hecto h • 101 E 1 deca da • 10-1 E -1 deci d • 10-2 E -2 centi c • 10-3 E -3 milli m • 10-6 E -6 micro ｵ • 10-9 E -9 nano n • 10-12 E-12 pico p

  9. The First Cell • Earth formed @ 4.5 billion years ago • Life emerged @ 3.8 billion years ago • No or little oxygen • CO2 and N2; H2, H2S and CO • Add heat and water • Organic molecules • LIFE! ????????

  10. The First Cell • Proteins and RNA were thought to be the first macromolecules produced • Only RNA capable of directing its self-replication, acting as both template and catalyst • “RNA World” existed for a period of time • The FIRST CELL is thought to have arisen when RNA became enclosed in a phospholipid membrane, and was able to self-replicate

  11. Evolution of Metabolism • The early Earth lacked O2 • Early Cells took food and energy by absorption • Glycolysis - glucose to lactic acid • Photosynthesis - sunlight, water, CO2 to Glucose and O2 • Oxidative metabolism - Glucose and O2 to CO2 and water • ATP is generated • All Cells use ATP for energy to drive their cellular machinery

  12. Prokaryotes today • Two groups • Archaea and the Eubacteria (true bacteria) • Archaea live in many harsh environments • Eubacteria populate many places • Bacterial shapes vary, as does their size and DNA content

  13. 01_10_Bacteria shapes.jpg

  14. 01_11_E. Coli.jpg

  15. 01_13_Sulfur bacterium.jpg

  16. Eukaryotic Cells • Also have a plasma membrane and ribosomes - just as do Prokaryotes • Nucleus, with linear chromosomes • Organelles - mitrochondria, chloroplasts, lysosomes, peroxisomes. • Plant cells have vacuoles for storage, waste, or digestion of macromolecules • ER (endoplasmic reticulum) & Golgi apparatus • Cytoskeleton - network of protein filaments

  17. 01_14_Yeasts.jpg Yeast Cell budding

  18. 01_15_Nucleus.jpg Nucleus

  19. Origin of Eukaryotes • Hypothesis that a critical step in the evolution of eukaryotic cells took place possibly via two endosymbiotic events - one cell living inside another • Some of the organelles are thought to have evolved from prokaryotes living inside eukaryotes

  20. 01_18_folds mito.jpg

  21. 01_19_engulfed bacteria.jpg

  22. 01_20_Chloroplasts.jpg

  23. 01_21_Chloro.engulfed.jpg

  24. Mitochondria & Chloroplasts • Same size as bacterial cells • Reproduce by dividing into two, like bacteria • Both contain their own DNA, coding for some of their own components • Have own ribosomes too, which more closely resemble those of bacteria, then those in the cell cytoplasm.

  25. PREVIEW OF WHAT’S TO COME Schematic of typical animal cell, showing subcellular components. Organelles: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles

  26. 01_22_ER.jpg

  27. 01_23_Golgi apparatus.jpg

  28. 01_24_Organelles.jpg

  29. 01_25_endocytosis exoc.jpg

  30. 01_27_cytoskeleton.jpg Actin, microtubules, intermediate filaments

  31. 01_29_eucaryotes origin.jpg

  32. Multicellular Organisms • Many eucaryotes are unicellular just like bacteria • Single cells capable of self-replication • Simplest eucaryotes are the yeasts (6um & 12 million bps) • Amoeba is 100,000x the volume of typical E.coli bacteria • Over a Billion years ago (> 1 x 10E9) multi-cellular organisms evolved from single celled eukaryotes • Volvox shows an evolutionary transition phase, of multiple cells aggregating for the greater good.

  33. Multicellular Volvox (algae)

  34. Multicellular Organisms cont… • Plants have fewer specialized cells than do animals • Ground tissue - includes parenchyma cells (metabolism including photosynthesis), and collenchyma and sclerenchyma cells (which are rigid and provide structure) • Dermal tissue - covers the surface of the plant and provides protection and diffusion • Vascular tissue - elongated cells form the xylem and phloem for transport

  35. Multicellular Organisms cont… • Animal cells are more diverse & specialized • Human body contain over 200 different kinds of cells • Epithelial cells - sheets that cover the body and line the gut • Connective tissues - bone, cartilage, adpose • Blood and immune systems • Nerve cells and brain

  36. Reading assignments to stay current Read Chapter 1 of textbook to page 23 & visit website for supplemental information (time @ 55 minutes)

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