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Chapter 1

A Preview of the Cell Modified by Dr. J. Jordan. Chapter 1. The Cell Place. www.thecellplace.com Student access codes in front of every new text. Introduction. Cell Basic unit of life Cells have the capacity to grow, reproduce, and specialize

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Chapter 1

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  1. A Preview of the Cell Modified by Dr. J. Jordan Chapter 1

  2. The Cell Place • www.thecellplace.com • Student access codes in front of every new text.

  3. Introduction • Cell • Basic unit of life • Cells have the capacity to grow, reproduce, and specialize • Respond to stimuli and adapt to changes in the environment • Rapidly changing field of science • Cell biology – cytology, genetics, and biochemistry

  4. History of Cell • Story of cell biology started about 300 years ago • European scientists • Crude microscopes

  5. The Cell Theory: A Brief History • Robert Hooke (1665) observed compartments in cork, under a microscope, and first named cells (the basic unit of biology) • He focused on empty cell walls of dead plant tissues (cork) not plant tissues filled with “juices” • His observations were limited by the low magnification power(30X enlargement) of his microscope. • Magnification – increase in the size of a specimen in comparison to normal size. Can you see internal structure of the cell at 30X?

  6. History continued • Antonie van Leeuwenhoek, a few years later, produced better lenses that magnified up to 300X • First to observe living cells • Blood cells, sperm cells, bacteria, and single-celled organisms in pond water

  7. Early progress in cell biology was slow • Two factors restricted progress in early cell biology • Microscopes had limited resolution or resolving power (ability to see fine detail) • The descriptive nature of cell biology; the focus was on observation, with little emphasis on explanation

  8. Microscopes: essential tools in early cell biology • By the 1830s, compound microscopeswere used (two lenses). What are they? • Increased magnification and resolution • Structures only 1 micrometer in size could be seen • Can you see individual cells without a microscope? • Animal cells is 20 micrometers (µm) • Bacterium about 2 micrometers • One inch equals about 25,000 micrometers

  9. Using a compound microscope, Robert Brown (botanist)identified the nucleus, a structure inside plant cells • Matthias Schleidenconcluded that all plant tissues are composed of cells, and Thomas Schwann made the same conclusion for animals cells • They proved that plants and animal cells are similar structurally. • Name some things that are similar; different?

  10. Figure 1A-1

  11. The cell theory • In 1839, Schwann postulated the cell theory • 1. All organisms consist of one or more cells • 2. The cell is the basic unit of structure for all organisms • Later, Virchow (1855) added • 3. All cells arise only from preexisting cells

  12. Properties of Cells • Wide variety of shapes and sizes of cells • Fungal cells • Bacterial cells • Reproductive cells • Nerve cells

  13. Figure 1-1

  14. Figure 1-1 a-c

  15. Figure 1-1 d,e

  16. Figure 1-1 f

  17. Figure 1-1 g-i

  18. The Cell • Cell is not only the basic unit of structure for all organisms but also the basic unit of reproduction • Remember movie: Children of Men • We must study cells to understand biology • Cell structure gives us clues to cell function

  19. The Emergence of Modern Cell Biology • Three historical strands weave together into modern cell biology, each with important contributions to understanding cells • The cytology strand focuses mainly on cellular structure, and emphasizes optical techniques • The biochemistry strand focuses on cellular function • The genetics strand focuses on information flow and heredity

  20. Figure 1-2

  21. The Cytological Strand Deals with Cellular Structure • Historically, cytology deals primarily with cell structure and observation using optical techniques

  22. The Light Microscope • The light microscope was the earliest tool of cytologists • Allowed identification of organelles within cells • Organelles are membrane-bound structures, such as nuclei, mitochondria, and chloroplasts

  23. Useful tools in early microscopy • Themicrotome(mid-1800s) allowed preparation of very thin slices of samples • A variety of dyes for staining cells began to be used around the same time • These improved the limit of resolution(how far apart objects must be to appear as distinct) • The smaller the limit of resolution a microscope has, the greater its resolving power

  24. Visualization of Cells • The light microscopy so far described is called brightfield microscopy, as white light is passed through a specimen • Some preparations (fixing, staining, embedding in plastic) may distort tissues • Various types of microscopy have been developed to allow observation of living cells

  25. Visualizing living cells • Phase contrast/differential interference contrastmicroscopyexploit differences in the phase of light passing through a structure. Helps you see living cells clearly • Fluorescence microscopydetects fluorescent dyes, or labels, to show locations of substances in the cell • Confocal scanninguses a laser beam to illuminate a single plane of a fluorescently labeled specimen

  26. Figure 1-3

  27. Table 1-1

  28. The Electron Microscope • Theelectron microscope, using a beam of electrons rather than light, was a major breakthrough for cell biology • The limit of resolution of electron microscopes is around 0.1-0.2 nm • The magnification is much higher than light microscopes up to 100,000X

  29. Electron microscopy • In transmission electron microscopy (TEM),electrons are transmitted through the specimen • In scanning electron microscopy (SEM),the surface of a specimen is scanned, by detecting electrons deflected from the outer surface • Specialized approaches in electron microscopy allow for visualization of specimens in three dimensions, and one allows visualization of individual atoms

  30. Figure 1-4a

  31. Figure 1-4b

  32. Figure 1-4c

  33. Figure 1-4d

  34. Electron Microscopy • EM is normally used on samples that are fixed (parafilm) and coated with metal (gold). • Most cases of TEM and SEM samples are dead or will die due to the electron beam • EM has revolutionized our understanding of cellular structures(ribosomes)

  35. The Biochemical Strand Covers the Chemistry of Biological Structure and Function • Around the same time cytologists were studying cells microscopically, others began to explore cellular function • Much of biochemistry dates from the work of FredrichWöhler (1828), who showed that a compound made in a living organism could be synthesized in the lab. • Urea can be synthesized from ammonium cyanate

  36. Developments in early biochemistry • Louis Pasteur (1860s) showed that living yeast cells could ferment sugar into alcohol. What is this called? • The Buchners (1897) showed that yeast extracts could do the same • Led to the discovery of enzymes, biological catalysts. Specifically how do they function?

  37. Early discoveries in biochemistry • Steps of the pathways of fermentation and others were elucidated in the 1920s and 1930s • Gustav Embden and Otto Meyerhof described the steps of glycolysis (the Embden-Meyerhof pathway) in the early 1930s • The Krebs cycle (TCA) was described soon after by Hans Krebs • Both pathways are important in energy metabolism of cells • Also Fritz Lipmann, showed theat ATP is principle energy source in cells

  38. Important advances in biochemistry • Radioactive isotopes - to trace the fate of specific atoms and molecules (led to elucidation of the Calvin cycle, 1950s) • 3H, 14C, and 32P were first used to trace the metabolic fate of specific atoms and molecules • Melvin Calvin used 14C-labeled carbon dioxide • Most common pathway for photosynthetic carbon metabolism. First pathway to use radioactivity

  39. Techniques • Subcellular fractionation • Use of Centrifugationto separate/isolate different structures and macromolecules based on size, shape, and density • Different types of centrifugation (described chp.12) • Ultracentrifuges - capable of very high speeds (over 100,000 revolutions per minute) • Just as significant as the electron microscope

  40. Ultracentrifuge

  41. Gel electrophoresis

  42. Important advances in biochemistry (continued): • Chromatography - techniques to separate molecules from a solution based on size, charge, or chemical affinity (pigments in 1107) • Electrophoresis- uses an electrical field to move proteins, DNA or RNA molecules through a medium based on size/charge • Mass spectrometry - to determine the size and composition of individual proteins

  43. The Genetic Strand Focuses on Information Flow • The genetic strand has important roots in the nineteenth century • Gregor Mendel’s experiments with peas (1866) laid the foundation for understanding the passage of “hereditary factors” from parents to offspring • The hereditary factors are now known to be genes • His work was not appreciated until 35 years after his discovery

  44. Chromosomes and the genetic material • Walther Flemming(1880) saw threadlike bodies in the nucleus called chromosomes • He called the process of cell division mitosis • Wilhelm Roux (1883) and August Weisman (shortly after) suggested that chromosomes carried the genetic material

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