Cell biology

• Eukaryotic cells


  Cells that contain their genetic material enclosed in a nucleus
• Eukaryotic cells


  • Contain a nucleus
  • Contain a cell membrane
  • Contain cytoplasm
• Prokaryotic cells


  Cells where the genetic material is not enclosed in a nucleus
• Prokaryotic cells


  • Do not have a nucleus
  • Have a cell membrane
  • Have a cell wall
  • Contain cytoplasm
  • May have plasmids
• Prokaryotic cells


  Are much smaller than eukaryotic cells
• Meter


  The base unit of measurement in science
• Sizes in biology


  • Often much smaller than a meter
• Centi


  One hundredth
• Centimeter (cm)


  One hundredth of a meter
• Size of objects


  • Width of little finger is around 1 cm
• Milli


  One thousandth
• Millimeter (mm)


  One thousandth of a meter
• Size of objects


  • Tip of a ballpoint pen is around 1 mm
• Micro


  One millionth
• Micrometer (μm)


  One millionth of a meter
• Size of objects


  • Typical human cell is 10-20 μm in size
• Nano


  One billionth
• Nanometer (nm)


  One billionth of a meter
• Size of objects


  • Hemoglobin molecule is around 5 nm in diameter
• Prefixes centi, milli, micro, and nano are used to describe sizes much smaller than a meter
• Smaller units like micrometers and nanometers are particularly useful for describing the size of cells and their components
• Specialized animal cells


  Cells that have adaptations to help them carry out their particular function
• Differentiation


  The process where cells become specialized
• Sperm cells


  • Long tail to swim to ovum
  • Packed with mitochondria to provide energy for swimming
  • Contain enzymes to digest outer layer of ovum
• Fertilization


  The process where the genetic information of the ovum and sperm combine
• Nerve cells


  • Long axon to transmit electrical impulses
  • Axon covered in myelin to insulate and speed up transmission
  • Dendrites to increase surface area for connections
• Nerve impulses


  Electrical signals transmitted by nerve cells
• Muscle cells


  • Contain protein fibers that can contract and shorten the cell
  • Packed with mitochondria to provide energy for contraction
• Muscle tissue


  Formed from many muscle cells working together
• Differentiation

  The process where cells become specialized
• Root hair cells

  • Increase the surface area of the root to absorb water and dissolved minerals more effectively
  • Do not contain chloroplasts
• Xylem cells

  • Have very thick walls containing lignin to provide support
  • Have no internal structures like nucleus, cytoplasm, vacuole or chloroplasts to allow easy flow of water and dissolved minerals
• Phloem cells

  • Consist of two types: phloem vessel cells with no nucleus and limited cytoplasm, and companion cells with mitochondria to provide energy to the phloem vessel cells
  • Phloem vessel cells have porous end walls called sieve plates to allow flow of dissolved sugars
• Specialized plant cells include root hair cells, xylem cells, and phloem cells
• Specialized plant cells have adaptations that allow them to carry out their specific functions
• Photosynthesis requires energy from light, so root hair cells which are underground cannot perform photosynthesis
• Xylem cells form long tubes to carry water and dissolved minerals from roots to leaves
• Phloem tubes carry dissolved sugars up and down the plant
• Optical microscope


  Used to look at cells on a prepared microscope slide
• Optical microscope


  • Has a stage to place the microscope slide
  • Has a light source (lamp or mirror) to illuminate the slide
  • Has objective lenses with different magnifications (4x, 10x, 40x)
  • Has an eyepiece lens with 10x magnification
  • Has coarse and fine focusing dials