Cell Theory

• The study of etymology deals with origin and history of words
• Biology


  The study of life
• The total human body cells is around 100 trillion cells
• Prokaryotes

  Organisms with no membrane-bound nucleus, have a nucleoid
• Eukaryotes

  Organisms with membrane-bound nucleus, have mitochondria, membrane bound organelles, linear DNA
• Differences between prokaryotes and eukaryotes

  • No membrane-bound nucleus vs membrane-bound nucleus
  • No mitochondria vs have mitochondria
  • No membrane bound organelles vs have membrane bound organelles
  • Circular DNA vs linear DNA
  • Unicellular vs unicellular or multicellular
  • Binary fission vs meiosis or mitosis
• Prokaryotes are unicellular organisms, eukaryotes can be unicellular or multicellular
• Prokaryotes reproduce by binary fission, eukaryotes reproduce by meiosis or mitosis
• Prokaryotes have naked and circular DNA, eukaryotes have protein-bound and linear DNA
• Four fundamental concepts of cell theory

  • All living cells are composed of cells
  • The cell is the basic functional unit of life
  • Cells arise only from pre-existing cells
  • Cells carry genetic information in the form of DNA
• Viruses do not reproduce on their own, they need a host, and their genetic information is RNA not DNA
• Levels of biological organisation

  1. Cells

  2. Tissues

  3. Organs

  4. Systems