cell differentiation and stem cells

• a sperm is a specialised animal cell that fuses with an egg cell to fertalize it


  -the head contains a nucleus containing genetic material for fertilisation and has an arcosome (stores enzyme to break down outer layer of egg)

  -has flagellum (tail) for movement

  -middle section is full of mitochondria
• Nerve cell/Neurone is a specialised cell in an animal that carries electrical impulses around the body


  -have dendrites to make connection to other nerve cells

  -has axon (carries impulses away from body)

  -synapse (nerve endings) pass impulses to other nerve cells and contain many mitochondria to transfer energy
• Muscle cells are specialised cells in an animal that contract and relax to help bring about movement 


  -contain special proteins that slide over each other making fibres contrast

  -many mitochondria to transfer energy

  -can store glycogen (can be broken down into glucose for respiration)
• Red blood cells are specialised cells in an animal that transort oxygen around the body


  -has biconcave shape disc with a thin centre to allow the cell to flow smoothly through narrow blood vessels

  -lacks a nucleus for more surface area

  -contains haemaglobin (a red pigment) which binds with oxygen to carry oxygen where it is needed
• a root hair cells is a specialised plant cell found close to the tip of growing roots to help uptake water and mineral ions


  -have large surafce area to help plants take up water and mineral ions faster

  -larger vaccuole to speed up movement of water by osmosis
• Palisade cells are specialised plant cells found in the leaves to trap sunlight to help make food


  -has lots of chloroplast to help perform photosynethis

  -has a larger vacuole that helps the cell stay rigid for osmosis

  -positioned in continous layers to absorb more sunlight
• Phloem cells are specialised plant cells that transport food made by the leaves to the rest of the plant


  -supported by companion cells to keep them alive and consists of mitochondria

  -cell walls between the cells to break down to form special Sieve Plates
• Xylem cells are specialised plant cells that transports water and mineral ions from the root to the higest leaves and shoots


  -made of dead cells forming long, hollow tubes that trabsports water and mineral ions

  -consists of lignin spirals providing support for the plants
• Differentation occurs when an uninspected cell changes into a cell with special features to carry out specific functions (specialised cells)
• a stem cell is a cell that is not specialised and can be divided to produce lots more undifferentiated cells and can also differentiate into different types of cells depending on what instruction they are given
• embryonic stem cells can turn into ANY type of cell
• Stem cells are found in early human embryos and in certain places like bone marrow in adults
• Unlike embryonic stem cells, adults can't turn into any cell type at all, only certain ones like blood cells
• Stem cells from emrbyos and bone marrow can be grown in labs to produce clones (genetically identical cells) and made to differentiate into specialised cells to use in medicine and reasearch
• Stem cells may be able to cure many diseases
• Stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in the patient who receives them
• therapeutic cloning


  1. remove both nucleus
  2. put the doner's nucleus into the egg cycle
  3. electrical stimulation triggers the start of mitosis
  4. after 5 days, the cell is harvested and placed back in the patient's body
• therapetic cloning


  could produce stem cells with the same genetic make ups as the patient. The technique involves the transfer of the nucleus from a cell of the patient to an egg cell.
• What is a clinical issue associated with therapeutic cloning?

  There is no guarantee of success in therapies using stem cells.
• Why is finding suitable stem cell donors a challenge?

  There is a current difficulty in finding suitable stem cell donors.
• What is a challenge in obtaining a patient’s embryonic stem cells?

  They must be collected before birth, which is difficult.
• What service do some clinics offer regarding umbilical cord blood?

  Some clinics offer to store blood from the umbilical cord at birth.
• What mutations have been observed in cultured stem cells?

  Mutations have been observed in stem cells cultured for several generations.
• How can mutated stem cells behave inappropriately?

  Some mutated stem cells have been observed to behave like cancer cells.
• What risk is associated with cultured stem cells regarding contamination?

  Cultured stem cells could be contaminated with viruses.
• What are the main clinical issues with therapeutic cloning?

  • Uncertain success of therapies using stem cells
  • Difficulty in finding suitable stem cell donors
  • Challenges in obtaining and storing embryonic stem cells
  • Mutations in cultured stem cells behaving like cancer cells
  • Risk of contamination with viruses