Cell Theory

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Cell Theory

  1. 1. Cell Theory Stephen Taylor i-Biology.net Image: Cells by Filter Forge on Flickr http://flic.kr/p/ePXpR5
  2. 2. All living things are made of C E L L S Longitudinal section of a root tip of Maize (Zea mays) by Science and Plants for Schools on Flickr (CC) http://flic.kr/p/bNNM6M
  3. 3. All living things are made of Unicellular organisms are singlecelled and can carry out all of the functions of life independently. Multicellular organisms have specialized cells to carry out specific functions. C E L L S Longitudinal section of a root tip of Maize (Zea mays) by Science and Plants for Schools on Flickr (CC) http://flic.kr/p/bNNM6M
  4. 4. C E L L S are the smallest units of life. Paramecium multimicronucleatum by Proyecto Agua on Flickr (CC) http://flic.kr/p/7W7J3y
  5. 5. C E L L S are the smallest units of life. Specialized structures within cells (organelles) carry out different functions. Organelles cannot survive alone. Paramecium multimicronucleatum by Proyecto Agua on Flickr (CC) http://flic.kr/p/7W7J3y
  6. 6. C come only E from L existing cells. L S 4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS
  7. 7. C come only E from L existing cells. L S Cells multiply through division. All life evolved from simpler ancestors. Mitosis results in genetically identical diploid daughter cells. Meiosis generates haploid gametes (sex cells). Pasteur disproved the theory of spontaneous generation with his experiments. 4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS
  8. 8. 1665 Hooke names “cells” in his book “Micrographia” after observing cork under a lense. All living things are made of cells. Hooke’s Micrographia in full! http://lhldigital.lindahall.org/cdm/ref/collection/nat_hist/id/0
  9. 9. All living things are made of cells. 1676 van Leeuwenhoek, a master microscope maker identifies “animalcules” and becomes the father of microbiology. http://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek
  10. 10. 1833 Robert Brown names the cell nucleus. Cells are the smallest units of life. He also discovered Brownian motion: Robert Brown: http://en.wikipedia.org/wiki/Robert_Brown_(botanist) http://en.wikipedia.org/wiki/Brownian_motion
  11. 11. 1855 Robert Remak discovers cell division and confirms the existence of the plasma membrane. Cells come only from pre-existing cells. Robert Remak: http://en.wikipedia.org/wiki/Robert_Remak
  12. 12. 1864 Pasteur disproves the prevailing theory of “spontaneous generation” with his swan-neck flask experiments. Populations need to be seeded by existing populations: cells come only from pre-existing cells. Image from Amoeba Mike’s Blog (go read the original post): http://amoebamike.wordpress.com/2009/10/06/spontaneousgeneration-a-brief-history-of-disproving-it
  13. 13. Labeling the parts of the microscope activity: http://www.biology.ualberta.ca/facilities/multimedia/uploads/intro-biology/microscope.html
  14. 14. Magnification The image we see through the light microscope has been magnified. Objective lens x eyepiece lens Image from wikimedia commons: http://commons.wikimedia.org/wiki/File:Microscope-blank.svg
  15. 15. Modern Microscopy Image: d2540-6 by USDA on Flickr (CC): http://flic.kr/p/dPqvvY
  16. 16. Modern Microscopy As we develop more and more sophisticated and precise imaging tools, we can see more detail of the cells and molecules that make us. Scanning electron microscopes deliver highresolution, 3D surface images of structures, whereas transmission electron microscopes give us a view inside cells and organelles. Image: d2540-6 by USDA on Flickr (CC): http://flic.kr/p/dPqvvY
  17. 17. Emiliana huxleyi Image from: http://earthguide.ucsd.edu/earthguide/imagelibrary/emilianiahuxleyi.html
  18. 18. Transmission electron micrograph of HIV particles. 120nm HIV-1. Transmission electron micrograph, via wikimedia commons: http://commons.wikimedia.org/wiki/File%3AHIV1_Transmission_electron_micrograph_AIDS02bbb_lores.jpg
  19. 19. Scanning electron micrograph of HIV particles budding on a human lymphocyte. 1μm False-coloured scanning electron micrograph of HIV (green) budding on a lymphicoyte (blue) http://en.wikipedia.org/wiki/File:HIV-budding-Color.jpg OR http://phil.cdc.gov/phil/details.asp?pid=10000
  20. 20. Unicellular Organisms carry out all the functions of life M ovement R espiration S ensitivity G rowth R eproduction E xcretion N utrition Paramecium bursaria by Proyecto Agua on Flickr (CC) http://flic.kr/p/7WXdFz
  21. 21. Given the right conditions, cells can survive outside their normal habitat. Art from Petri dishes_1 by Image in Science and Art on Flickr (CC) http://flic.kr/p/838xjC
  22. 22. VIRUSES Are they living or non-living? Hmm….. Image: Swine Flu H1N1 virus influenza 9.0 by hitthatswitch on Flickr (CC) http://flic.kr/p/74e4SP
  23. 23. Some units that I use & know Unit abbr. Metric equivalent kilometer km 1,000m 1 x 103m meter m 1m 1m centimeter cm 0.01m 1 x 10-2m mm 0.001m 1 x 10-3m millimeter micrometer nanometer μm nm write this correctly 0.000 001m 0.000 000 001m 1x 10-6m 1x 10-9m μm = micrometers We usually use this in discussion of cells. There are 1,000μm in one mm. X 1,000 ÷1,000 ÷1,000 ÷1,000
  24. 24. 50μm Human egg cell, from Gray’s Anatomy (1858). http://commons.wikimedia.org/wiki/Gray%27s_Anatomy_plates
  25. 25. 5μm Human sperm cell, from Gray’s Anatomy (1858). http://commons.wikimedia.org/wiki/Gray%27s_Anatomy_plates
  26. 26. Scanning electron micrograph of human sperm and egg cells. 5μm Image from wikimedia commons http://en.wikipedia.org/wiki/Spermatozoon
  27. 27. Which dissolves faster: sugar cubes or sugar crystals? Why? Sugar Cubes by Uwe Hermann on Flickr (CC) http://flic.kr/p/cFMMc
  28. 28. What will go cold faster: French fries or a baked potato? Why? French Fries by Ian Britton on Flickr (CC) http://flic.kr/p/6RLQ8j
  29. 29. Which makes green tea faster: tea leaves or powder? Matcha Latte by Cupcake Murder Aftermatch on Flickr (CC) http://flic.kr/p/fCkpb5
  30. 30. What type of crisps delivers more flavour: regular-cut or crinkle-cut? Why? Smiths Plain Chips by Penguin Cakes on Flickr (CC) http://flic.kr/p/5ygb8v
  31. 31. IN:  Oxygen  Nutrients  Water The plasma membrane of a cell is the surface of exchange for materials between the inside and the outside of the cell. OUT:  Carbon dioxide  Waste  Products (e.g. proteins) http://commons.wikimedia.org/wiki/Sphere
  32. 32. As the cell gets larger, it requires more resources to be imported and produces more products (and waste) to be exported. Therefore, a larger volume requires more exchange across the membrane. http://commons.wikimedia.org/wiki/Sphere
  33. 33. As the cell gets larger… http://commons.wikimedia.org/wiki/Sphere
  34. 34. As the cell gets larger… …the surface area to volume ratio actually gets smaller… http://commons.wikimedia.org/wiki/Sphere
  35. 35. As the cell gets larger… …the surface area to volume ratio actually gets smaller… …so the exchange processes become less efficient with increasing size. http://commons.wikimedia.org/wiki/Sphere
  36. 36. Diffusion Pathways are shorter (and more efficient) in with a larger surface are to volume ratio. http://commons.wikimedia.org/wiki/Sphere
  37. 37. C E L L S D I V I D E Surface are to volume ratio is a factor that limits the size of cells. By dividing to make more, smaller cells, the efficiency of the exchange processes across the membranes (into and out of the cells) can be kept high. Shorter diffusion paths. More surfaces for reactions. Removal of heat and waste 4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS
  38. 38. Structure/Function Natural selection favours adaptations that give an advantage. Folded structures are everywhere in nature, maximising the surface area to volume ratio for exchange of materials. Mammalian liver mitochondria: http://commons.wikimedia.org/wiki/File:Mitochondria,_mammalian_lung_-_TEM_(2).jpg
  39. 39. Big Cell Exceptions Caulerpa species of algae are one giant cell with many nuclei distributed throughout. http://en.wikipedia.org/wiki/Caulerpa
  40. 40. Big Cell Exceptions Epulopiscium is a giant species of bacteria. Read more about it here: NotExactlyRocketScience. E. coli 100μm Epulpoiscium, by AJ Cann on Flickr (CC) http://flic.kr/p/4Nzq9t
  41. 41. Is maximising surface area to volume ratio always an advantage? Free images from: Presentations ETC, University of Florida. http://etc.usf.edu/presentations/
  42. 42. Two Minute Essay Explain the importance of surface area to volume ratio as a factor limiting cell size. Free images from: Presentations ETC, University of Florida. http://etc.usf.edu/presentations/
  43. 43. Exploration: which cools faster? Add 30ml hot water to a small cup and to a petri dish. Predict: Will one cool faster? Why? Record: Take the temperature of each one every minute. Describe or plot the results. 30ml 30ml
  44. 44. Design an investigation into the effect of SA:Vol ratio on exchange of…
  45. 45. Emergent Properties the whole is more than the sum of its parts Photo by Stephen Taylor: http://www.flickr.com/photos/gurustip/9668701965/in/photostream
  46. 46. Stem Cells A cluster of nascent retinae generated from 3D embryonic stem cell cultures, by UCL News on Flickr (CC): http://flic.kr/p/ffPBPT
  47. 47. A Stem Cell Story http://www.youtube.com/watch?v=2-3J6JGN-_Y
  48. 48. Stem Cells retain the capacity to divide and can differentiate along divergent pathways. Totipotent Can differentiate into any type of cell. Pluripotent Can differentiate into many types of cell. Multipotent Can differentiate into a few closely-related types of cell. Unipotent Can regenerate but can only differentiate into their associated cell type (e.g. liver stem cells can only make liver cells). Image from: http://en.wikipedia.org/wiki/Stem_cell
  49. 49. Stem Cells retain the capacity to divide and can differentiate along divergent pathways. By Fwfu at en.wikibooks [Public domain], from Wikimedia Commons http://commons.wikimedia.org/wiki/File%3AStemcelldifferentiaion.jpg
  50. 50. Stem Cells retain the capacity to divide and can differentiate along divergent pathways. Screenshot from this excellent tutorial: http://www.ns.umich.edu/stemcells/022706_Intro.html
  51. 51. Differentiation (specialization) of cells: All diploid (body) cells have the same chromosomes. So they carry all the same genes and alleles. BUT Not all genes are expressed (activated) in all cells. The cell receives a signal. This signal activates or deactivates genes. Genes are expressed accordingly and the cell is committed. Eventually the cell has become specialized to a function. Key Concept: Structure vs Function How do the structures of specialized cells reflect their functions? How does differentiation lead to this? Screenshot from this excellent tutorial: http://www.ns.umich.edu/stemcells/022706_Intro.html
  52. 52. Therapeutic Uses of Stem Cells Treatment for Leukemia Problem Treatment Chemotherapy and radiotherapy can be used to destroy the white blood cells, but these need to be replaced with healthy cells. Bone marrow transplants are often used for this. Role of Stem Cells From: Cancer of the blood or bone marrow, resulting in abnormally high levels of poorlyfunctioning white blood cells. Hematopoetic Stem Cells (HSCs) can be harvested from bone marrow, peripheral blood or umbilical cord blood. As these can differentiate to form any type of white blood cell, they can be used to repopulate the bone marrow and produce new, healthy blood cells. The use of a patient’s own HSCs means there is far less risk of immune rejection than with a traditional bone marrow transplant. http://en.wikipedia.org/wiki/Pluripotential_hemopoietic_stem_cell Animation of this process: Animated tutorials from: http://outreach.mcb.harvard.edu/animations/thera7c.swf
  53. 53. Two Minute Essay What is a stem cell? How do stem cells differentiate into specialized cells? Outline one therapeutic use of stem cells. Free images from: Presentations ETC, University of Florida. http://etc.usf.edu/presentations/
  54. 54. For more resources & links including many on Stem Cells. Please consider a donation to charity via Biology4Good. Click here for more information about Biology4Good charity donations. This is a Creative Commons presentation. It may be linked and embedded but not sold or re-hosted.

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