Tuesday, January 18, 2011

Cell and Life



Cell is the fundamental unit of life.
It took a lot of time for organisms to be multi cellular. This is because cells needed a way to communicate with each other and for a such mechanism to evolve it took time.
Life is a concept that is hard to define. However there are certain activities that can be used to define life.

Activities that define life;


  1. Adaptation
  2. Order and Organization
  3. Metabolism ( anabolism and catabolism)
  4. Responsiveness
  5. Reproduction
  6. Movement
  7. Heredity
  8. Evolution
  9. Growth and development
  10. Death


There are three linages of modern day organisms

  1. Bacteria
  2. Archae
  3. Eukaryotes


The former two linages comes under Prokaryots who lack a defined nucleus. Prokaryotes have a simple cellular organization.
Eukaryotes have a membrane bound nucleus which contains most of the cellular DNA. They have specialized organelles and a complete cytoskeleton.

even though eukaryotes and prokaryotes are different they share a number of structural and functional properties such as;

  • Structure of biomembranes
  • structure of DNA
  • The process of DNA replication
  • The process of Protein synthesis
  • Production of ATP


Stem cells
Found in multicellular organisms. Able to renew themselves from mitotic division and differentiate into a diverse range of specialized cells.
Two broad types of mammalian stem cells are;

  1. Embryonic stem cells (Isolated from the inner cell mass of Blastocysts, 5 days after Morula)
  2. Adult stem cells (found in adult tissues)

Plants also have stem cells in;

  1. Shoot tips
  2. Root tips

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