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 get colour images
• Transmission electron microscopes


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


  Similar to transmission electron microscopes, but the electrons bounce 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 inside the eyepiece of a microscope that can be used to measure the size of objects
• Calibrating the eyepiece graticule


  1. Align it with a stage micrometer

  2. Count how many eyepiece divisions fit in one stage micrometer division

  3. Calculate the value of one eyepiece 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


  A differential staining technique used to identify whether bacteria are gram-positive or gram-negative
• Scientific drawings


  Accurate, labelled diagrams showing the size, shape, and location of structures, without shading or colour
• Transmission electron microscopes


  Use a beam of electrons that pass through a very thin specimen to create a 2D image
• Scanning electron microscopes


  Use a beam of electrons that bounce off the surface of the specimen to create a 3D image
• Laser scanning confocal microscopes


  Use a laser to scan the specimen and create a high resolution 3D image
• Eukaryotic cell organelles


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


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


  • Provide mobility and sensory functions
• Centrioles


  • Involved in spindle fibre formation during cell division
• Cytoskeleton


  • Provides mechanical strength, shape and stability to the cell, anchors organelles
• Endoplasmic reticulum


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


  • Modifies, packages and distributes proteins and other molecules produced in the ER
• 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 form cisternae, vesicles bud off the edges, proteins are processed and packaged, carbohydrates added to proteins, secretory enzymes made, lipids modified and stored, molecules labelled with destination
• Lysosomes


  Vesicles containing digestive enzymes, can fuse with phagosomes to hydrolyse 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
  • Contains mitochondrial matrix, site of aerobic respiration and ATP production
  • Contains own ribosomes and DNA
• Ribosomes


  Small, made of protein and RNA subunits, 80S in eukaryotes, 70S in prokaryotes and organelles, site of protein synthesis
• Chloroplasts


  • Double membrane-bound organelle
  • Thylakoid membranes stacked into grana
  • Contains fluid stroma with enzymes for photosynthesis
• Cell walls


  Found in plant and fungal cells, provide structural strength, made of cellulose microfibrils 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 and packaged into vesicles

  3. Vesicles transported to Golgi apparatus for further modification

  4. Proteins packaged into secretory vesicles

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


  • Smaller, no membrane-bound organelles, circular DNA not in nucleus, 70S ribosomes, cell wall made of murein, some have plasmids, capsule, flagella
• Biological molecules


  • Carbohydrates (contain C, H, O)
  • Lipids (contain C, H, O)
  • Proteins (contain C, H, O, N, sometimes S)
  • Nucleic acids (contain C, H, O, N, P)
• Water


  Polar molecule, forms hydrogen bonds, important as solvent, transport medium, coolant, habitat provider
• Monomers


  Smaller units that can bind together to form polymers
• Polymers


  Larger molecules made up of many monomers bonded together