Stem cells

• What are Stem cells?

  Stem cells are undifferentiated cells that can develop into other types of cell.
• What are stem cells used for?

  They are used by organisms for growth, development and tissue repair. 
• Stem cells have two key features: 

  1. Stem cells can divide by mitosis to produce more undifferentiated cells. 
  2. Stem cells can differentiate into specialised cells.
• Label this diagram

  A) Differentiation

  B) Mitosis

  
• What are the 4 types of Stem cells

  Totipotent Stem cells

  Pluripotent Stem cells

  Multipotent Stem cells

  Unipotent Stem cells
• What are Totipotent Stem cells?

  Stem cells that can differentiate into any cell type and go on to form whole organisms. Including the Placenta
• What are Pluripotent Stem cells?

  These stem cells can differentiate into most cell types, but cannot form whole organisms or the Placenta
• What are Multipotent Stem cells?

  These Stem cells can only differentiate into a few different cell types.
• What are Unipotent Stem cells?

   These Stem cells can only differentiate into one type of cell. 
• Locations of Stem cells

  Embryonic stem cells 

  Adult stem cells 

  Plant stem cells 
• Embryonic stem cells 

  • Found in the early stages of embryo development where they can differentiate into cells to form a foetus.
  • In the first few divisions of the embryo, the stem cells are totipotent.
  • After about 7 days, these stem cells become pluripotent.
• Adult stem cells 

  • Found in some adult tissues where they can replace faulty cells.
  • Stem cells are multipotent or unipotent. 
  • Stem cells in the bone marrow replace worn out erythrocytes (red blood cells) and neutrophils (white blood cells). 
• Plant stem cells

  • Found in the meristematic tissue or meristems at the tips of the shoots and roots of plants.
  • Stem cells are pluripotent.
  • Meristematic tissue is also found between phloem and xylem tissues in an area known as the vascular cambium.
  • These stem cells differentiate into cells of the xylem and phloem.  
• Stem cells can also be used for the following purposes: 

  • Testing new drugs - Drugs can be tested for toxicity and side effects before being tested on humans. 
  • Studying development of organisms - Scientists can find out how organisms grow and develop from a single cell. 
  • Identifying causes of disorders - Scientists can identify when something goes wrong in an organism's development.