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 high 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 for light microscopes


  • 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, and location of structures, without shading or colour
• Electron microscopes


  Use a beam of electrons to create high resolution images, but require the specimen to be in a vacuum
• Transmission electron microscopes


  Electrons pass through a very thin specimen, creating a 2D image
• Scanning electron microscopes


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

  Use a laser to scan the specimen and create high resolution 3D images
• Organelles in eukaryotic cells

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


  • Contains DNA, site of DNA replication and transcription
  • Contains nucleolus where ribosomes are synthesized
• Flagella and cilia


  • Provide mobility and sensory functions
• Centrioles


  • Involved in spindle fibre formation during cell division
• Cytoskeleton


  • Provides mechanical strength and stability, 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
• 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 and lysosomes
• Vesicles from Golgi apparatus


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


  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
  • 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. Polypeptides synthesized on rough ER

  2. Packaged and folded in ER

  3. Transported to Golgi apparatus

  4. Modified and packaged into vesicles

  5. Vesicles fuse with cell membrane to release proteins
• Prokaryotic cells


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


  • No membrane-bound organelles
  • Circular DNA not in a nucleus
  • Smaller 70S ribosomes
  • Cell wall made of murein
  • May have plasmids, capsule, flagella
• Biological molecules contain carbon, plus other elements