BIOL220

• who discovered cells


  Cells first discovered by Robert Hooke (1665) in cork bark
• what is the cell theory and the info behind it

  • Hooke used the term “cell” because the tiny compartments reminded him of a monk’s cell
  • “Cell” comes from the Latin cellameaning “small room”
  • Due to sample studied, Hooke observed cell walls of dead cells
• viruses vs cell theory

  Viruses don’t cell propagate, they take over another cell (don’t arise from existing cells)
• history of cell theory

  • In the mid-1800s a general theory emerged about the nature and significance of cells
  • In 1838, German botanist Matthias Schleiden confirmed that plant parts are composed of cells(cell walls made it easy to identify individual cells)
  • In 1839, German biologist Theodor Schwann confirmed that animals are also composed of cells
• scheliden and Schwann "cell theory"

  1. Organisms are made up of one or more cells
  2. The cell is the basic unit of structure for all organisms
  3. New cells arise only from existing cells
• early microscopes

  • Hooke was able to observe cork cells in 1665 using microscope developed by Antoine van Leeuwenhoek
  • The single lens (small glass ball) microscope was able to magnify 300X
  • In 1676, van Leeuwenhoek reported the discovery of microorganisms
• light microscope


  Light Microscopes increase magnification as light passes through a series of transparent lenses made of glass/calcium fluoride crystals. Includes compound and dissecting microscopes
• compound microscope

  • Compound microscopes magnify up to 1500X and can distinguish organisms > 2 μm in diameter.
  • Light must be able to pass through specimen, need to use thinly sliced material. In the lab you will be using a Leica DM750
• dissecting microscope

  • Dissecting (stereo-) microscopes have lowermagnification (30X) but allow three-dimensional viewing of opaque objects
  • more of a handheld magnifying glass
• electron microscopes

  • Electron Microscopes (1920’s) enhance resolution by using a beam of electrons to visualize samples.
  • They are however,bulky, expensive, and require chemical preservation and skill
  • doesn't allow for colour in images
• transmission electron microscopes


  Transmission Electron Microscopes (TEM) magnify200,000X and require specimen to be sectioned very thin,<100 nm.
• scanning electron microscope

  • Scanning Electron Microscopes (SEM) magnify10,000X and can obverse surface of thick specimens.
  • SEM image is thick
  • for 3D things
• Fluorescence microscope

  Fluorescence microscopes use fluorescence to generate an image. Magnify up to 1500X and allow study of living cells.
• what are the 2 types of fluorescence microscope

  confocal and epifluorescence
• epifluorescence microscope

  • Epifluorescence microscopes are equippedwith xenon arc or mercury vapour lamps toexcite fluorescent compounds, fluorophores
  • excite all cell layers
  • light coming from bottom so it gets hazy
• confocal microscope

  • Confocal microscopes use lasers to generateoptical sections of thick specimens. Developed in the 1960’s, but isolation of green fluorescentprotein (GFP) in the 90’s, increased its popularity.
  • specify the layer you are looking for (thick)
  • excite one layer
  • observing living cells and the activity of fluorescent proteins
• what is Autofluorescence in plant tissues


  Autofluorescence is the florescence of naturally

  occurring substances in plants and animals.

  Allows visualization of cell structures and organelles via fluorescence without staining or introduction of transgenic fluorescent proteins
• cell membrane

  • Semi-permeable barriers that control movement of substances in and out. Cell membranes are fluid and flexible
• carbohydrates in cell membrane

  Carbohydrates are attached or embedded in phospholipid bilayer. Provide structure support and cell recognition (cell-to-cell, cell-to-pathogen)
• proteins in cell membrane

  Proteins embedded in phospholipid bilayer control selective transport across membrane, function as receptors and serve as attachment sites
• phospholipid bilayer

  • Phospholipid bilayer made up of hydrophobic (“water hating”) fatty acid tails and hydrophilic (“water loving”) phosphate heads
  • Small things can pass through phospholipid bilayer but big things through proteins
• plasma membrane


  Plasma membranes separatethe interior of a cell from theiroutside environment. on inside of cell wall
• organelles


  Organelles are distinct cell structures with specific function that are surrounded by one or two membranes.
• nucleus

  • The nucleus is the site of DNA storage and translation; the nucleolus in centresynthesizes ribosomes.
  • The nucleus is an organelle surrounded by a double membrane known as the nuclear envelope.
  • Can observe nucleus and nucleolus on low microscope
• cytoplasm


  Cytoplasm is all the cell contents within theplasma membrane excluding the nucleus.

  • Is grainy under microscope 
• cytosol


  Cytosol is the fluid portion of cytoplasm.
• protoplasm


  Protoplasm is the cytoplasm and thenucleus (entire living cell).
• protoplast

  Protoplast can refer to the living cell withinthe cell wall or plant cells that have had theircell walls enzymatically removed.
• Cytoplasmic organelles (distinct structures surrounded by one to two membranes) shared by plants and animals

  • ribosomes
  • ER
  • Golgi
  • mitochondria
  • vesicles
• ribosomes


  sites of protein synthesis that “read” mRNA
• Endoplasmic reticulum 


  Endoplasmic reticulum transportation system and protein folding
• Golgi


  Golgi arranged into dicytosome (plant) or golgi apparatus (animals), modify proteins from ER and package into vesicles. like stacked pancakes
• mitochondria


  Mitochondria perform aerobic respiration to produce ATP
• Vesicles


  Vesicles contain liquid or cytoplasm, used for storage or transport
• plastids

  • Plastids make or store food and/or pigment
  • Chloroplast is a type of plastid
  • Not all plastids are chloroplast
• leucoplasts


  Leucoplasts are pigment-free plastids thatsynthesize and store starch (amyloplast),oil (elaioplast) and protein (proteinoplast)
• chromoplasts


  Chromoplasts (Greek chroma =colour)are pigmented plastids responsible fortissue colour (leaves, flowers and fruits).Pigments can be chlorophyll (green),carotenoid (yellow, orange, red), andanthoxanthin (yellow)
• chloroplasts

  • Chloroplasts are chromoplasts that contain chlorophyll pigment (latin chloro = “yellow-green”) and are the site of photosynthesis.• Have two (2) membranes and acircular chromosome• Have series of internal, membrane-bound sacs called thylakoidsFig.9.5. Elodea sp. leaf 400X mag
  • Cells can have 1-100’s of chloroplasts
• interconversion


  Plastids can change from one type to another in a process known as interconversion
• proplastids


  Proplastids are undifferentiated plastids; differentiation dependent on tissue, developmentalstage and environmental conditions (example: lightor no light).