Module 2

• Light/Optical microscopes


  • Poor resolution due to wavelength of light
  • Can use living samples
  • Can get color images
• Transmission electron microscopes


  • High magnification and resolution
  • Electrons pass through specimen to create image
• Scanning electron microscopes


  • Electrons bounce off surface to create 3D image
• Laser scanning confocal microscopes

  • High resolution and 3D
  • Use laser light to create image
• Resolution


  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
• Calibrating eyepiece graticule

  1. Align with stage micrometer

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

  3. Calculate value of one eyepiece division
• Magnification calculation


  Size of image / size of real object
• Staining

  Adds color to make cell components more visible
• Differential staining

  Uses multiple stains to color different cell components
• Gram staining


  Identifies gram-positive vs gram-negative bacteria
• Scientific drawings

  • Pencil only
  • Include title, magnification, annotations
  • Solid lines, no shading or coloring
• Electron microscopes


  • Use electron beam to create image
  • Require vacuum, image in black and white
• Transmission electron microscopes


  • Specimen must be very thin
  • Electrons pass through, darker areas absorb more electrons
• Laser scanning confocal microscopes

  • Use fluorescent dyes and laser to create 3D image
• Eukaryotic cell organelles


  • Nucleus
  • Flagella
  • Cilia
  • Centrioles
  • Cytoskeleton
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Mitochondria
  • Peroxisomes
  • Plastids
  • Vacuoles
  • Ribosomes
• Nucleus


  Contains DNA, site of replication and transcription
• Flagella


  Whip-like tail for cell mobility
• Cilia


  Hair-like projections, can be stationary or mobile
• Centrioles


  Microtubule structures involved in spindle formation for cell division
• Cytoskeleton


  Network of microfilaments, microtubules and intermediate fibers providing structure and movement
• Endoplasmic reticulum


  Rough ER - site of protein synthesis, Smooth ER - site of lipid and carbohydrate synthesis
• Golgi apparatus


  Modifies, packages and distributes 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
• Golgi apparatus


  Folded membranes that process and package proteins, can modify them further e.g. add carbohydrates, create secretory vesicles
• Golgi apparatus


  • Slightly more curved shape than ER
  • Vesicles budding off the edges
• Golgi apparatus function


  1. Protein processing and packaging

  2. Protein modification e.g. adding carbohydrates

  3. Creation of secretory vesicles

  4. Lipid transport, modification and storage

  5. Enzyme secretion
• Lysosomes


  Vesicles containing digestive enzymes, can fuse with phagosomes to hydrolyse pathogens, break down dead cells
• Mitochondria


  • Double membrane-bound organelle
  • Inner membrane folds to create cristae
  • Contains own ribosomes and DNA
• Mitochondria


  Site of aerobic respiration and ATP production
• 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
  • Internal thylakoid membranes stacked into grana
  • Contains fluid-filled stroma with enzymes for 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 synthesised on ribosomes of rough ER

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

  3. Vesicles transported to Golgi apparatus for further modification

  4. Modified proteins packaged into secretory vesicles

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


  • Smaller size
  • No membrane-bound organelles
  • Circular DNA not in a nucleus
  • Smaller 70S ribosomes
  • Cell wall made of murein
• Additional prokaryotic cell features

  • Plasmids
  • Capsule
  • Flagellum