Cell Division

• Cell theory


  • 1. A cell is the smallest unit of life
  • 2. Cells make up all living things
  • 3. New cells can arise only from preexisting cells
• Domains that include prokaryotic cells

  • Bacteria
  • Archaea
• Kingdoms that include eukaryotic cells

  • Protists
  • Fungi
  • Plants
  • Animals
• Organelles


  Components within a cell that carry out specific functions
• Difference between prokaryotic and eukaryotic cells (in terms of organelles)

  • Eukaryotic cells have membrane-bound organelles, whereas prokaryotic cells do not
• Other differences between prokaryotic and eukaryotic cells

  • Prokaryotic cells are smaller than eukaryotic cells
  • The DNA of prokaryotic cells is circular, whereas it is found in linear strands in eukaryotic cells
  • DNA in prokaryotic cells is found in the cytoplasm, whereas it is found in the nucleus of eukaryotic cells
  • Prokaryotic cells rarely have internal membranes, whereas eukaryotic cells have many
• Micrometer


  1/1,000,000 of a meter
• Why small cells are more efficient than large cells

  • Small cells have a high surface-to-volume ratio, which means that all nutrients and wastes can be moved in and out of a cell efficiently
• Types of microscopes


  • Light microscope
  • Electron microscope
• Micrograph


  A photograph obtained using a microscope
• Staining cells


  Increases the contrast between different components of cells
• Structure of a cell


  Reflects its functions
• Functions of a cell

  Reflects its structure
• Plasma membrane


  Controls the movement of substances into and out of the cell
• Orientation of phospholipids in plasma membrane

  The phospholipids form a bilayer where the hydrophilic heads face the outside and inside of the cell (water-based) and the hydrophobic tails face inwards towards each other
• Extracellular fluid


  Interstitial fluid (between tissues)
• Other biomolecules associated with plasma membrane

  • Proteins
  • Carbohydrates
• Structure of plasma membrane

  Selectively permeable
• Selectively permeable


  Some substances are permitted entry into the cell, whereas others are not
• Other functions of plasma membrane

  • Maintain structural integrity of the cell
  • Provide recognition between cells
  • Provide communication between cells
  • Stick cells together to form tissues and organs
• Eukaryotic cell diagram and component functions
• Types of cytoskeleton fibers

  • Microtubules (thickest)
  • Intermediate filaments
  • Microfilaments (thinnest)
• Centrioles


  Made up of nine sets of three microtubules arranged in a ring. Each cell contains a pair of centrioles.
• Functions of microfilaments


  • Muscle contraction (sliding filaments made of actin)
  • Cell division (form the band that pinches the cell in two)