Biology

• There are four different types of microscopes: light/optical, transmission electron, scanning electron, and laser scanning confocal
• Light/Optical microscopes


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


  • Much higher magnification and resolution
  • Electrons pass through the specimen to create an image
• Scanning electron microscopes


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

  • High resolution and 3D
  • Use laser light to create the 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 different colors
• Gram staining


  Identifies gram-positive (purple) vs gram-negative (red) bacteria
• Scientific drawings


  Accurate pencil drawings showing size, shape, and location of structures, without shading or coloring
• Electron microscopes


  • Use a beam of electrons to create the image
  • Require a vacuum to prevent air from absorbing electrons
  • Images are black and white
• Transmission electron microscopes


  • Specimen must be very thin
  • Electrons pass through and are absorbed differently to create 2D image
• Scanning electron microscopes


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

  • Use high intensity fluorescent light to create 3D image by scanning point-by-point
• Eukaryotic cell organelles


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


  Contains DNA, site of DNA replication and transcription
• Flagella


  Whip-like tail structure for cell mobility
• Cilia


  Hair-like projections, can be stationary (sensory) or mobile (sweeping substances)
• Centrioles


  Involved in spindle fiber formation during cell division
• Cytoskeleton


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


  Rough ER is site of protein synthesis, smooth ER is site of lipid and carbohydrate synthesis
• Golgi apparatus


  Processes, packages and modifies proteins and lipids, creates secretory vesicles
• Lysosomes


  Contain digestive enzymes to break down molecules
• Mitochondria


  Site of cellular respiration, produce ATP
• Peroxisomes


  Contain enzymes to break down toxic substances
• Plastids


  Found in plant cells, include chloroplasts for photosynthesis
• Vacuoles


  Storage compartments, can be contractile or hold waste
• Ribosomes


  Site of protein synthesis
• Rough endoplasmic reticulum


  Has ribosomes on the outside
• Smooth endoplasmic reticulum


  Has folded membranes but no ribosomes on the outside
• Golgi apparatus


  Has folded membranes making cisternae, slightly more curved in shape than smooth ER, has vesicles budding off the edges
• Golgi apparatus function


  Proteins are processed and packaged, carbohydrates added to proteins to make glycoproteins, secretory enzymes made, lipids transported, modified and stored, molecules labelled with destination, finished products released in vesicles
• Lysosomes


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


  • Double membrane-bound organelle, inner membrane folds to create cristae, site of aerobic respiration and ATP production, contains own ribosomes and DNA
• Ribosomes


  Small, made of protein and RNA, 80S ribosomes in eukaryotic cytoplasm, 70S ribosomes in prokaryotes and organelles, site of protein synthesis
• Chloroplasts


  • Double membrane, internal folded membranes called thylakoids stacked into grana, fluid-filled stroma containing enzymes for photosynthesis