Stem Cells

• Stem cells


  Cells that have the ability to divide and produce different types of cell
• Stem cells


  • Most stem cells are very simple cells in animals and plants that have the ability to divide to form cells of the same type
  • Animals have two types of stem cell: adult stem cells that can divide to form cells of the same general type, and embryonic stem cells from embryos or the umbilical cord that can form the full range of cells in the body
  • Following a number of divisions, animal stem cells develop into specialised cells which are adapted for particular functions
  • In plants, stem cells originate in the meristems (the rapidly dividing zones at shoot and root apices, or tips), and many plant cells (not only those at meristems) retain the ability to divide and so can be used in cloning techniques
• Leukaemia


  A type of cancer of the blood
• Bone marrow transplants as a form of treatment for leukaemia


  Stem cells in the bone marrow from a donor contain the ability to produce the different types of blood cell in the right proportions (which doesn't happen in leukaemia)
• Potential benefits of using stem cells in medicine


  • Diseases such as leukaemia can be treated
  • Replacement of body parts, including replacement organs
• Potential risks and ethical considerations of using stem cells in medicine


  • Pre-treatment can involve radiotherapy and/or chemotherapy, which can kill healthy cells as well
  • Transfer of viruses or diseases from other animals
  • Formation of tumours or the development of unwanted cell types
• Peer review


  Where scientific research is checked by other scientists of at least equal standing, who often provide advice to allow the research to be improved upon
• Stem cell research (as with all scientific research) needs to be validated through peer review
• Adult stem cells


  • Can divide to form cells of the same general type, e.g. stem cells in the bone marrow only form the different types of blood cell
• Embryonic stem cells


  • From embryos or the umbilical cord
  • Can form the full range of cells in the body
• Stem cells in animals

  • Figure 1.4
• Following a number of divisions, animal stem cells


  Divide into specialised cells which are adapted for particular functions, e.g. nerve cells
• Plant stem cells


  • Originate in the meristems (the rapidly dividing zones at shoot and root apices, or tips)
  • Many plant cells (especially those at meristems) retain the ability to divide and so can be used in biotechniques
• Leukaemia is a type of cancer of the blood
• Bone marrow transplants are used to treat leukaemia
• Stem cells

  • Important in medical research on cell differentiation and drug testing
• Leukaemia

  Blood cancer
• Bone marrow

  Spongy material that fills the bones, contains early blood cells called stem cells
• Blood cell production

  1. Stem cells in bone marrow keep dividing to make new blood cells

  2. Keeps blood cell numbers in normal range
• Chemotherapy drugs

  Reduce red blood cell, white blood cell and platelet counts
• White blood cell count

  Goes down first due to shortest life span
• Stem cell transplants

  Replace bone marrow to enable production of new healthy blood cells
• Healthy bone marrow

  • Leukaemia
• The use of embryonic stem cells involves the destruction of laboratory-fertilised human eggs
• For those who believe life begins at conception, destroying the fertilised egg is immoral and unacceptable
• Long-term effects of interfering with nature through stem cell technology are unknown
• Potential risks and ethical considerations of stem cell use

  • Body recognises embryonic stem cells as 'different' and will reject them without drugs
  • May produce cancer cells instead of healthy cells
  • Adult stem cells difficult to find and extract from tissue
• Stem cell research is under strict control in most countries to protect the public
• Stem cell research needs to be validated through peer review
• Advantages of using embryonic stem cells over adult stem cells

  • Easier to grow or culture
  • More plentiful and easier to extract
  • Can develop into a wider range of cell types and tissues
  • More in placenta and umbilical cord than adult bone marrow
• Stem cells in plants

  Found in apical growing points (roots/shoots) or meristems, retain ability to divide until final position reached, can be reversed to produce genetically identical plants
• Stem Cells in plants

  
• Cell


  Basic building block of living organisms e.g. animal cell
• Tissue


  • Group of cells with similar structures and functions e.g. skin, muscle
• Organ


  • Groups of different tissues working together to form a structure with a particular function e.g. brain
• Organ system


  • Different organs organised into a system e.g. the nervous system
• Organism


  • Different organ systems make up the organism e.g. human
• Most organisms have become multi-celled, making them much larger than single cells
• Organisms need a large enough surface area (a large surface area to volume ratio)


  To be able to effectively exchange substances with their environment
• Large active multi-celled organisms have developed special gas exchange organs inside their body (lungs) which have greatly increased the surface area