Biology 1

• Microscopes


  Instruments that form an image of an object by using a beam of light or electrons
• Microscopes developed


  Mid 17th Century
• Light microscopes


  • Form an image of an object by a beam of light, up to 2000x magnification
• Electron microscopes


  • Form an image by a beam of electrons, up to 2000000x magnification
• TEM (Transmission Electron Microscope)

  • Produces 2D images, high magnification, high resolution, can look at sub-cellular structures
• SEM (Scanning Electron Microscope)

  • Produces 3D images, large depth of field, can examine surface structure of specimens
• Magnification


  How many times bigger an object is in an image compared to real life
• Resolution


  The ability to distinguish between two separate points, how detailed the image appears
• Light microscope resolution = 200nm, SEM resolution = 1nm, TEM resolution = 0.2nm
• Calculating magnification


  1. Image Size / Actual Size

  2. Actual Size x Magnification = Image Size
• Eukaryotic cells


  • Animal, plant, fungi, protista cells, have cell membrane, cytoplasm, ribosomes and DNA stored in nucleus, size 10-100 μm
• Prokaryotic cells


  • Single-celled organisms like bacteria and archaea, have cell membrane, cytoplasm, ribosomes and DNA as a single loop in cytoplasm plus plasmids, size 0.7-20 μm (1-2 orders of magnitude smaller than eukaryotic cells)
• Order of magnitude


  Using powers of 10, if one number is 10x bigger than another it is 1 order of magnitude bigger
• Calculating order of magnitude

  1. Divide bigger number by smaller number

  2. If result is less than 10 = same order of magnitude

  3. If result is around 10 = 1 order of magnitude bigger

  4. If result is around 100 = 2 orders of magnitude bigger
• Diffusion


  Spreading out of particles of gas or substance in a solution, resulting in net movement from high to low concentration across a semi-permeable membrane
• Factors affecting rate of diffusion

  • Greater concentration gradient = faster rate
  • Increase in temperature = faster rate
  • Larger surface area = faster rate
• Gas exchange and diffusion

  1. Oxygen diffuses from alveoli in lungs into blood capillaries

  2. Oxygen diffuses from blood capillaries into muscle cells

  3. Carbon dioxide diffuses from muscle cells into blood capillaries

  4. Carbon dioxide diffuses from blood capillaries into alveoli and is breathed out
• Osmosis


  Movement of water across a partially permeable membrane from a dilute solution to a concentrated solution
• Isotonic solution


  Concentration of solutes outside the cell is equal to the internal concentration, no net movement of water
• Hypotonic solution


  Concentration of solutes outside the cell is lower than internal concentration, water moves out of the cell, can cause cell to shrink and die
• Hypertonic solution


  Concentration of solutes outside the cell is higher than internal concentration, water moves into the cell, can cause the cell to burst
• Active transport


  Cells move substances from low to high concentration, against the concentration gradient, requires energy
• Active transport and respiration

  Cells with high levels of mitochondria have a higher rate of respiration to provide energy for active transport
• Examples of active transport


  • Root hair cells absorbing mineral ions from soil
  • Gut epithelial cells absorbing glucose from gut into blood
• Surface area to volume ratio

  Cells need a large surface area to volume ratio to have sufficient transport of molecules in and out to meet the demands of the organism