Chapter 1

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?

7. 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

8. 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

9. 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

11. 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?

12. Figure 1A-1

13. 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

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

15. Figure 1-1

16. Figure 1-1 a-c

17. Figure 1-1 d,e

18. Figure 1-1 f

19. Figure 1-1 g-i

20. 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

21. 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

22. Figure 1-2

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

24. 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

25. 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

26. 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

27. 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

28. Figure 1-3

29. Table 1-1

30. 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

31. 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

36. Figure 1-4a

37. Figure 1-4b

38. Figure 1-4c

39. Figure 1-4d

40. 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)

41. 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

42. 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?

43. 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

44. 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

45. 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

46. Ultracentrifuge

47. Gel electrophoresis

48. 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

49. 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

50. 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