Cell structure

• Cells are the Basic Structural Unit of All Living Things
• Cell Theory

  1. All living things are composed of cells.

  2. Cells are the basic units of structure and function.

  3. Cells come from preexisting cells.

  
• Deductive Reasoning

  • Reaching conclusions from general ideas

  Making predictions based on previous conclusions
• All known organisms are composed of at least one cell
• All newly discovered organisms will be composed of at least one cell
• Deductive reasoning is a logical approach where you progress from general ideas to specific conclusions
• Magnification

  The size of the image compared to the actual size of the object
• Resolution

  The ability of a microscope to distinguish details of a specimen or sample

  
• Calculating Magnification


  Measure the length of the scale bar

  Note the actual length of the scale bar

  Input the measured length and actual length into the magnification formula

  Convert the measured length to nm

  Calculate the magnification
• 1000μm = 1mm, 1μm = 1 x 10-6m, 1000nm = 1 μm, 1 nm = 1 x 10 -9m
• Calculate the Length of the Mitochondrion

  Calculate the magnification using the scale bar

  Measure the actual length of the mitochondrion in mm, and convert to nm

  Use the rearranged magnification formula to calculate the actual length
• Electron Microscopes

  • Greater magnification and resolution

  Allows scientists to see greater detail within cells, so that small structures such as ribosomes can be seen

  
• The Nobel Prize for Chemistry was awarded for the development of the Cryogenic electron microscope in 2017
• Cryogenic electron microscopy allows scientists to view proteins and other biomolecules which do not readily crystalise
• Freeze Fracture Electron Microscopy

  Rapidly freeze biological samples

  Fracture in area of weakness, such as separating the phospholipid bilayer, and through integral proteins

  Allows analysis of the structure of plasma membranes and identification of integral proteins
• Fluorescent Stains and Immunofluorescence in Light Microscopy

  Bind specific antibodies chemically attached to a fluorescent dye to specific proteins within biological tissue

  Analyze the sample using a fluorescence microscope
• Advantages of Immunofluorescence

  • Fluorescent stains are specific, so scientists are able to study the location, distribution and quantity of specific biomolecules

  Fluorescent stains can be used with living tissue, allowing scientists to study dynamic processes
• Immunofluorescence

  Binding a specific antibody chemically attached to a fluorescent dye to visualize a specific protein or antigen in cells or tissue
• Immunofluorescence

  • Fluorescent stains are specific, allowing study of location, distribution and quantity of specific biomolecules
  • Can be used with living tissue to study dynamic processes
  • Can detect molecules at low concentrations
  • Different coloured fluorescent stains can be used to label different molecules allowing study of interactions
• Immunofluorescence is a technique used to visualize a specific protein or antigen in cells or tissue by binding a specific antibody chemically attached to a fluorescent dye
• The specific antibodies attach to specific proteins within biological tissue
• The sample can then be analyzed using a fluorescence microscope
• Electron microscope compared to light microscope

  • Greater magnification
  • Greater resolution
  • Ability to see smaller structures

  
• Cryogenic electron microscope


  Allows scientists to view biomolecules that do not readily crystalise
• Freeze fracture electron microscope

  Allows scientists to view the ultrastructure of rapidly frozen biological samples
• Immunofluorescent microscopy


  Technique involving binding a specific antibody chemically attached to a dye
• Fluorescent stains can only be used with living tissue
• Cells can be classified as prokaryotic cells or eukaryotic cells
• Features shared by all cells

  • Phospholipid plasma membrane
  • Cytoplasm composed mainly of water
  • DNA as genetic material
  • Ribosomes for protein synthesis
• Prokaryotic cells

  • Simple cell structure without compartmentalism
  • Diverse group of organisms with wide variety of structures
• Drawing a prokaryotic cell structure

  IB Biology students should be able to draw and annotate a diagram of a typical prokaryotic cell
• Prokaryotic cell structures


  • Cell wall
  • Plasma membrane
  • Cytoplasm
  • 70S ribosomes
  • Nucleoid region
  • Flagellum
  • Pilus
• Cell wall


  Provides the cell with strength and support, prevents the cell from bursting
• Cytoplasm


  Where most metabolism occurs, mostly composed of water
• Plasma membrane


  Controls what enters and exits the cell, composed of phospholipids
• 70S ribosomes


  Responsible for protein synthesis
• Nucleoid region


  Contains a single circular chromosome with DNA (no protein) that contains genetic information
• Flagellum


  Responsible for locomotion
• Pilus


  Allows bacteria to adhere to each other and other surfaces, and exchange genetic material
• Eukaryotic cells have chromosomes located in a nucleus, as well as a variety of membrane bound organelles