Cell Structure

• Cell


  The basic structural unit of all living organisms that carries out all the essential processes of life
• Characteristics of cells


  • Extremely small
  • All living organisms are made from cells
  • Some organisms are unicellular (made of single cells)
  • Some organisms are multicellular (made of many cells)
• Cell theory


  • All living things are composed of cells
  • The cell is the basic unit of life
  • Cells come from preexisting cells
• Viruses are not living and they are not made of cells
• Bacteria are living and they are made of cells
• Fungus are living and they are made of cells
• Animals are living and they are made of cells
• Plants are living and they are made of cells
• Subcellular components


  Not alive
• Multicellular organisms


  Have many cells of different types specialized for different functions
• Cell division


  1. Prokaryotic cells divide by binary fission

  2. Eukaryotic cells can divide through fission, mitosis or meiosis
• Conditions on Earth limit the ability of cells to spontaneously generate
• On Earth today, the only way to produce a new living thing is by reproduction of an existing one
• Inductive reasoning


  Developing theories from observations, using specific observations to form a general conclusion
• Deductive reasoning


  Using a general premise to form a specific conclusion
• Example of inductive reasoning


  • Cell theory
• Example of deductive reasoning


  • All organisms are made from one or more cells, slime molds are living organisms, therefore slime molds are made of cells
• A deduction will only hold true if the premises are correct
• Microscope


  A device that produces a magnified image of objects too small to be seen directly by the naked eye
• Magnification


  How much larger an object appears compared to its real size
• Total magnification


  Determined by multiplying the magnifying power of the ocular lens by the magnifying power of the objective lens
• Using a light microscope

  1. Turn rotating nosepiece to lowest power objective

  2. Place slide on stage and fasten

  3. Move stage up until objective almost touches slide

  4. Look through eyepiece and focus using coarse adjustment

  5. Move slide to centre sample

  6. Use fine adjustment to focus

  7. Adjust condenser and light as needed

  8. Change to higher power objectives, refocusing as needed
• Wet mount


  A drop of water is used to suspend the specimen between the slide and cover slip
• Staining


  Chemicals that bind to structures within the sample to make them show more clearly
• Field of view


  The diameter of the area visible through the microscope
• Determining field of view diameter


  1. Method 1: Measure directly using a ruler under low power

  2. Method 2: Calculate using equation for high/medium power
• Estimating size of specimen

  1. Method 1: Estimate fraction of field of view occupied

  2. Method 2: Estimate how many specimens would fit across field of view
• Drawing cells


  • Use pencil on white paper, center on page, make large clear drawing, use ruler for labels, avoid shading/coloring, include scale bar, draw what is seen not idealized
• Developments in microscopy have led to discoveries in biology
• Rudolf Virchow proposed that all cells come from other cells


  1855
• Anton von Leeuwenhoek discovers unicellular organisms


  1674
• Zacharias Jansen invents the compound microscope


  1590
• Light microscopes are most practical for school use due to ease of use and affordability
• Electron microscopes have higher magnification and resolution but are not practical for school use
• Microscopes


  Devices that produce a magnified image of objects too small to be seen directly by eyes
• The invention of the microscope (ca.1600) and its improvements over a period of 400+ years has resulted in great advances in our understanding of the microscopic world as well as extremely important advances in biology
• The microscope is a key instrument in basic science: it gives the observer a view of the world that cannot be observed with the naked eye because of insufficient resolution, such as atoms, molecules, viruses, cells, tissues, and microorganisms
• Robert Hooke discovers cells

  1663
• Theodore Schwann realizes all animals are made of cells


  1839
• Matthias Schleiden realizes all plants are made of cells


  1838