Biology 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 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 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 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
• Electron microscopes


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


  The specimen must be very thin, the image is created as electrons pass through
• Scanning electron microscopes


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


  Use a focused laser beam to scan the specimen and create a 3D fluorescent image
• Eukaryotic cell organelles


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


  • Contains DNA, 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 organelle positioning
• 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 molecules
• 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 process, package and modify proteins, can create vesicles
• Vesicles from Golgi apparatus


  • Bud off the edges of the Golgi apparatus
  • Fuse with cell membrane to release contents
• Lysosome


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


  • Double membrane-bound organelle
  • Inner membrane folds to create cristae
  • Contains own ribosomes and DNA
  • 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
  • Thylakoid membranes stack to form grana
  • Contains fluid 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. Polypeptides synthesized on RER ribosomes

  2. Polypeptides move to RER 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
• Prokaryotic cells


  • Smaller, no membrane-bound organelles, circular DNA not in nucleus, 70S ribosomes, cell wall made of murein
• Additional prokaryotic cell structures


  • Plasmids
  • Capsule
  • Flagellum
• Biological molecules contain carbon, plus other elements in varying proportions