B1

• Light microscope


  Microscope that uses light, small, easy to use, relatively cheap
• Resolution of light microscope


  Limited to 0.2 micrometers, any details less than 0.2 micrometers apart will appear blurry
• What light microscopes can be used to see

  • Individual cells like onion cells
• Electron microscope


  Microscope that uses electrons, really big, very expensive, hard to use, only used by scientists in laboratories
• Resolution of electron microscope

  Maximum resolution of 0.1 nanometers, 2000 times better than light microscopes
• What electron microscopes can be used to study

  • Sub-cellular structures like mitochondria
• Electron microscopes can give images with much higher magnifications without going blurry
• Comparing light and electron microscopes

  Electron microscopes have 2000 times better resolution than light microscopes
• Nanometers


  Smallest unit of length you need to know
• Units of length


  • Nanometers
  • Micrometers
  • Millimeters
  • Meters
  • Kilometers
• Each unit is 1,000 times bigger or smaller than the one next to it
• Converting between units of length

  1. Divide by 1,000 to convert to a larger unit

  2. Multiply by 1,000 to convert to a smaller unit
• To convert between non-adjacent units, convert in steps
• • Naked eye can see down to 100 micrometers
  • Light microscope can see down to 500 nanometers
  • Electron microscope can see down to 0.1 nanometers
• Centimeters


  10 millimeters, 100 centimeters in a meter
• Converting centimeters


  1. To meters: divide by 100

  2. To millimeters: multiply by 10
• Stem cells


  Cells that can divide by mitosis to form more cells and can differentiate into specialized cells
• Stem cells


  • Can divide by mitosis to form more cells
  • Can differentiate into specialized cells
• Human life starts


  1. Sperm cell fertilizes egg cell

  2. Forms zygote

  3. Zygote divides by mitosis repeatedly

  4. Forms embryo

  5. Embryonic stem cells can differentiate into any cell type

  6. Cells continue to divide and differentiate

  7. Leads to baby after 9 months
• Embryonic stem cells


  Stem cells found in the embryo that can differentiate into any cell type
• Adult stem cells


  Stem cells found in adults that can only differentiate into a narrow range of cell types
• Adult stem cells


  • Stem cells in bone marrow that can differentiate into blood cells
• Plant stem cells


  Stem cells found in meristem tissues of plants that can differentiate into all the cells and tissues the plant needs
• Plant stem cells persist for the plant's entire life, unlike embryonic stem cells which disappear by the time we're fully developed
• Multicellular eukaryotic organisms require a continuous supply of new cells for growth, development and repair
• The process through which these cells are generated is known as the cell cycle
• Cell cycle


  1. Growth

  2. DNA replication

  3. Mitosis and division (cytokinesis)
• DNA


  Usually spread out in long strings when cell is not dividing, condenses into chromosomes when cell starts to prepare for division
• Chromosomes

  • Packets of DNA, each containing a large number of genes that control development of different characteristics
  • Eukaryotic cells have two copies of each chromosome, one from mother and one from father
• Humans have 23 pairs of chromosomes, 46 in total
• Animals of different species can't reproduce to have fertile offspring due to different numbers of chromosomes
• Chromosome duplication


  1. Duplicate stays attached to original chromosome, forming an X shape

  2. Each chromosome is coloured half green to highlight the fact that the right half is a duplicate of the left half
• Chromosome alignment and separation

  1. Chromosomes line up along the center of the cell

  2. Fibers from either side of the cell attach to respective half of each chromosome and pull the arms to opposite sides, breaking the chromosomes in half
• Cell division (cytokinesis)


  1. Cell membrane and cytoplasm pull apart, forming two daughter cells

  2. Each daughter cell has the same DNA as the parent cell
• Daughter cells can then contribute to growth, development or repair and undergo the cell cycle all over again
• Binary vision


  The process by which prokaryotic organisms like bacteria divide and reproduce
• Binary fission


  1. How binary vision works

  2. Bacterial cell grows in size

  3. Replicates genetic material (large circular DNA strand and plasmids)

  4. Two circular DNA strands move to opposite sides of cell

  5. Plasmids arrange randomly

  6. New cell wall grows down middle of cell

  7. Cell divides into two new bacterial cells
• Binary fission is not the same as mitosis or meiosis, which happen in eukaryotic cells
• Bacterial cell


  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Large circular DNA strand
  • Plasmids (smaller circular DNA)
• Some bacteria


  • Have a flagellum (tail to move around)