Cells

• Organelles found in eukaryotic cells

  • Nucleus
  • Cell surface membrane
  • Mitochondria
  • Ribosomes
  • Golgi apparatus
  • Chloroplasts
  • Rough endoplasmic reticulum
  • Smooth endoplasmic reticulum
  • Lysosomes
  • Cytoplasm
  • Cell wall
  • Vacuole
• Nucleus


  • Contains chromosomes made up of wound up DNA, enclosed in a nuclear envelope
• Cell surface membrane


  • Made up of lipids and proteins, controls movement of things in and out of the cell
• Mitochondria


  • Has a double membrane, heavily folded inner membrane, site of respiration and ATP production
• Ribosomes

  • Small, found on rough ER or in cytoplasm, site of protein synthesis
• Golgi apparatus

  • Fluid-filled membrane, produces and transports new lipids and proteins
• Chloroplasts


  • Site of photosynthesis, have a double membrane and internal thylakoid membranes
• Rough endoplasmic reticulum

  • Similar to smooth ER but covered in ribosomes, site of protein processing
• Smooth endoplasmic reticulum


  • Site of lipid synthesis and processing
• Lysosomes

  • Contain digestive enzymes, kept separate from cytoplasm
• Cytoplasm

  • Where most cell reactions take place
• Cell wall


  • Maintains cell structure in plant cells
• Vacuole

  • Contains sap, helps maintain cell shape and pressure in plant cells
• Eukaryotic cell adaptations

  • Sperm cell has tail and many mitochondria
  • Epithelial cells have many villi
  • Fat cells store lipids
  • Red blood cells are concave with no nucleus
  • Nerve cells are very long
• Hierarchy of biological organisation

  • Cells
  • Tissues
  • Organs
  • Organ systems
• Structures in prokaryotic cells


  • Cytoplasm
  • Ribosomes
  • Cell surface membrane
  • Cell wall
  • Flagella
  • Circular DNA
  • Plasmids
• Prokaryotic cell DNA


  • Single circular strand in cytoplasm, not enclosed in nucleus
• Viral structures


  • Attachment proteins
  • Capsid
  • Nucleic acid (DNA or RNA)
  • Envelope
• Viruses


  Not cells, very small (20-300 nm), can only replicate inside living host cells
• Microscope scale


  • 1 mm = 1000 μm = 1,000,000 nm
  • 1 μm = 0.001 mm = 1000 nm
  • 1 nm = 0.001 μm = 0.000001 mm
• Optical microscope


  • Uses light, can view living specimens in colour, max magnification ~1500x
• Electron microscope


  • Uses electrons, gives black and white images of fixed dead specimens, max magnification ~1,500,000x
• Optical vs electron microscope images

  • Optical microscope image of Drosophila eye
  • Electron microscope image of Drosophila eye
• Parts of an optical microscope

  • Eyepiece
  • Base with light source
  • Coarse and fine focus knobs
  • Objective lenses
  • Stage to hold slide
• Optical microscope resolution


  Ability to differentiate between two spots, ~0.2 μm
• Transmission electron microscope


  • Very high resolution, requires very thin fixed specimens, images in vacuum
• Scanning electron microscope


  • Lower resolution, can image 3D fixed specimens
• Transmission electron microscope


  • Need a very thin specimen to image
  • Work on fixed samples
  • Samples have to be dead because it takes place inside a vacuum
  • Can get artifacts of scanning
• Scanning electron microscope


  • Have a lower resolution
  • Can be used to image 3D objects
  • Must have fixed samples
• Scanning electron microscope


  • Can see 3D image
  • Image is much thicker than transmission electron microscope sample
• Electron microscopes


  • Very large
  • Have their own dedicated room and air conditioning unit
  • Have a screen to look through but most images are computer generated
  • Samples go in the middle/bottom third of the equipment
  • Electrons come from the top and are focused by lenses before hitting the specimen
• Magnification calculation


  1. Magnification = Size of image / Actual size of object

  2. Convert all measurements to same scale (e.g. nanometers)

  3. Use eyepiece graticule to measure size of image
• Cell fractionation


  1. Homogenization to break down cell

  2. Filtration to remove large parts

  3. Ultracentrifugation to separate components by weight
• Cell cycle


  • Complete pathway from start to finish
  • Interphase is from cytokinesis to next nuclear envelope breakdown
  • 90% of cell cycle is interphase
• Interphase


  • G1 phase - cell growth and organelle production
  • S phase - DNA synthesis
  • G2 phase - more growth and organelle production
• Mitosis


  Produces two daughter cells with identical DNA
• Meiosis


  Produces four daughter cells with different DNA
• Stages of mitosis


  1. Interphase

  2. Prophase

  3. Metaphase

  4. Anaphase

  5. Telophase

  6. Cytokinesis
• Mitotic index = Number of cells in mitosis / Total number of cells
• Cancer


  • Uncontrolled cell division caused by mutations in cell cycle/division genes
  • Treatments aim to kill cancer cells by preventing DNA replication or metaphase