Module 2

• Light/Optical microscopes


  Have poor resolution due to the wavelength of light used to create the image, but can use living samples and produce colour images
• Transmission electron microscopes


  Have high magnification and resolution, using electrons passing through the specimen to create the image
• Scanning electron microscopes


  Similar to transmission electron microscopes, but use electrons bouncing off the surface to create a 3D image
• Laser scanning confocal microscopes

  High resolution and 3D, using laser light to create the image
• Resolution


  The minimum distance between two objects where they can still be viewed as separate
• Magnification


  How many times larger the image is compared to the actual object
• Slide preparation types


  • Dry mount
  • Wet mount
  • Squash slide
  • Smear slide
• Eyepiece graticule


  A scale within the eyepiece of a microscope used to measure the size of objects
• Calibrating the eyepiece graticule

  1. Align with stage micrometer

  2. Count divisions on eyepiece graticule that fit one division on stage micrometer

  3. Calculate value of one eyepiece graticule division
• Magnification calculation


  Size of image / Size of real object
• Staining


  Adding dyes to make cell components more visible under the microscope
• Differential staining


  Using multiple stains to colour different cell components different colours
• Gram staining


  Staining technique to identify gram-positive and gram-negative bacteria
• Scientific drawings


  Accurate, labelled diagrams showing size, shape, position and proportion, without sketching, shading or colouring
• Electron microscopes


  Use a beam of electrons to create the image, allowing higher resolution and visualisation of small organelles and structures
• Transmission electron microscopes


  Specimen must be very thin, electrons pass through and create a 2D image
• Scanning electron microscopes


  Electrons bounce off the surface of the specimen, creating a 3D image
• Laser scanning confocal microscopes

  Use a high intensity laser to illuminate a fluorescently stained specimen, creating a 3D image
• Eukaryotic cell organelles


  • Nucleus
  • Flagella
  • Cilia
  • Centrioles
  • Cytoskeleton
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Mitochondria
  • Peroxisomes
  • Plastids
  • Vacuoles
  • Ribosomes
• Eukaryotic cells include animal, plant and fungal cells
• Nucleus


  Contains the genetic material and is the site of DNA replication and transcription
• Flagella


  Whip-like tail structures for cell mobility
• Cilia


  Hair-like projections, either stationary for sensing or mobile for moving substances
• Centrioles


  Microtubule-based structures involved in spindle fibre formation during cell division
• Cytoskeleton


  Network of microfilaments, microtubules and intermediate filaments providing mechanical strength and structure
• Endoplasmic reticulum


  Folded membrane system, rough ER for protein synthesis, smooth ER for lipid and carbohydrate synthesis
• Golgi apparatus


  Folded membrane system that modifies, sorts and packages proteins and other materials
• Rough endoplasmic reticulum (RER)


  Site of protein synthesis because they have ribosomes on the outside, proteins can also be folded here
• Smooth endoplasmic reticulum (SER)

  Site of synthesis of lipids and carbohydrates, can also be used for storage
• Endoplasmic reticulum (ER)


  • Smooth folded membranes
  • Rough membranes have ribosomes attached on the outside
• Golgi apparatus


  Folded membranes that form cisternae, vesicles bud off the edges, proteins are processed and packaged here, can modify proteins by adding carbohydrates, create secretory vesicles and lysosomes
• Lysosomes


  Vesicles containing digestive enzymes, can fuse with phagosomes to hydrolyze and destroy pathogens, involved in breaking down dead cells, contents released by fusion with cell membrane
• Mitochondria


  • Double membrane-bound organelle
  • Inner membrane folds to form cristae
  • Site of aerobic respiration and ATP production
  • Contains own ribosomes and DNA
• Ribosomes


  • Small organelles made of protein and RNA, where protein synthesis occurs
  • 80S ribosomes in eukaryotes, 70S ribosomes in prokaryotes and organelles
• Chloroplasts


  • Double membrane-bound organelle
  • Thylakoid membranes stack to form grana
  • Site of photosynthesis
• Cell wall


  Provides structural strength, made of cellulose in plants, chitin in fungi
• Plasma membrane


  Phospholipid bilayer with embedded proteins, controls what enters and exits the cell
• Protein production and secretion

  1. Polypeptide chains synthesized on rough ER/ribosomes

  2. Polypeptides move to ER lumen and are folded/packaged into vesicles

  3. Vesicles transported to Golgi apparatus for further modification

  4. Proteins packaged into secretory vesicles

  5. Secretory vesicles fuse with cell membrane and release proteins by exocytosis
• Prokaryotic cells


  • Smaller, no membrane-bound organelles
  • Circular DNA not in a nucleus
  • 70S ribosomes
  • Cell wall made of murein
• Prokaryotic cell features


  • No membrane-bound organelles
  • Circular DNA not in a nucleus
  • 70S ribosomes
  • Cell wall made of murein
  • May have plasmids, capsule, flagella