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• Biologists use microscopes and the tools of biochemistry to study cells

  
• Eukaryotic cells


  • Have internal membranes that compartmentalize their functions
• Eukaryotic cell's genetic instructions

  • Housed in the nucleus and carried out by the ribosomes
• Endomembrane system


  • Regulates protein traffic and performs metabolic functions in the cell
• Mitochondria and chloroplasts


  • Change energy from one form to another
• Cytoskeleton


  • A network of fibers that organizes structures and activities in the cell
• Extracellular components and connections between cells


  • Help coordinate cellular activities
• All organisms are made of cells
• The cell is the simplest collection of matter that can be alive
• Even when cells are arranged into higher levels of organization, the cell remains the organism's basic unit of structure and function
• All cells are related by their descent from earlier cells
• Light microscope (LM)


  Visible light is passed through a specimen and then through glass lenses, which refract (bend) the light to magnify the image
• Microscopy parameters


  • Magnification, resolution, contrast

  
• LMs can magnify effectively to about 1,000 times the actual size of the specimen
• Improvements in light microscopy have included new methods for enhancing contrast, such as staining or labeling cell components to stand out visually
• The resolution barrier prevented cell biologists from using standard light microscopy to study organelles, the membrane-enclosed structures within eukaryotic cells
• Size range of cells

  • Atoms
  • Small molecules
  • Lipids
  • Proteins
  • Ribosomes
  • Viruses
  • Smallest bacteria
  • Mitochondrion
  • Most bacteria
  • Nucleus
  • Most plant and animal cells
  • Human egg
  • Frog egg
  • Chicken egg
  • Length of some nerve and muscle cells
  • Human height
• Brightfield microscopy


  Unstained specimen
• Brightfield microscopy


  Stained specimen
• Scanning electron microscopy (SEM)

  Focuses a beam of electrons onto the surface of a specimen, providing 3-D images

  
• Transmission electron microscopy (TEM)

  Focuses a beam of electrons through a specimen to study the internal structure of cells
• Recent advances in light microscopy, such as confocal and deconvolution microscopy, have sharpened images of three-dimensional tissues and cells

  
• As "super-resolution microscopy" becomes more widespread, the images we'll see of living cells may be as awe-inspiring as Van Leeuwenhoek's were 350 years ago

  
• Cell fractionation


  Takes cells apart and separates major organelles and other subcellular structures from one another
• Cell fractionation enables researchers to prepare specific cell components in bulk and identify their functions, a task not usually possible with intact cells
• Biochemistry and cytology complement each other in correlating cell function with structure
• Cell fractionation technique


  1. Homogenization

  2. Centrifugation

  3. Differential centrifugation
• The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic
• Organisms with prokaryotic cells

  • Bacteria
  • Archaea
• Organisms with eukaryotic cells

  • Protists
  • Fungi
  • Animals
  • Plants
• Basic features shared by all cells

  • Plasma membrane
  • Cytosol
  • Chromosomes
  • Ribosomes
• Prokaryotic cells


  • No nucleus
  • DNA in an unbound region called the nucleoid
  • No membrane-bound organelles
  • Cytoplasm bound by the plasma membrane
• Eukaryotic cells


  • DNA in a nucleus bounded by a membranous nuclear envelope
  • Membrane-bound organelles
  • Cytoplasm in the region between the plasma membrane and nucleus
• Eukaryotic cells are generally much larger than prokaryotic cells
• Plasma membrane


  Functions as a selective barrier that allows passage of enough oxygen, nutrients, and wastes to service the entire cell
• As a cell (or any other object) increases in size


  Its volume grows proportionately more than its surface area
• Smaller objects


  Have a greater ratio of surface area to volume
• Eukaryotic cell


  • Has extensive and elaborately arranged internal membranes that divide the cell into compartments (organelles)
• Total surface area


  Sum of the surface areas (height x width) of all box sides x number of boxes
• Total volume


  Height x width x length x number of boxes