Stem Cells (WJEC GCSE Biology)
Revision Note
Stem Cells
The term stem cell can be defined as follows:
An undifferentiated cell that has the ability to divide an unlimited number of times
Stem cells can give rise to different cell types through the process of differentiation
These different cell types are known as specialised cells; these cells are adapted to carry out specific functions
Specialised cells allow the bodies of multicellular organisms to function
Types of stem cell
The cells in mature tissues generally lose the ability to divide and differentiate, but some groups of stem cells remain:
In plants stem cells are found in the tips of growing roots and shoots
The tissue in these regions is known as meristem tissue
In animals, there are two broad categories of stem cells
Embryonic stem cells are found in early embryos; they have the potential to differentiate into any cell type
Adult stem cells are only found in certain locations, e.g. bone marrow, and can only differentiate into a few different cell types
They are predominantly used to replace old cells and repair damaged tissue
Animal stem cell types table
Stem cell type | Source | Potential of cell | Can give rise to cell types |
|---|---|---|---|
Embryonic stem cells | The inside layer of an embryo | Retains ability to differentiate | All the different types of specialised cells found in the body |
Adult stem cells | Bone marrow | Limited ability to differentiate | Cells of the blood, e.g. red blood cells, white blood cells |
Skin | Limited ability to differentiate | Cells found in the different layers of the skin | |
Other organs, e.g. liver and brain | Limited ability to differentiate | Cells found in these organs | |
Umbilical cord blood | Limited ability to differentiate | Cells of the blood, muscle and nerve tissue |
Stem cells in medicine
Stem cell technology has the potential to allow the repair of damaged organs in medical treatments
New tissue could be grown from stem cells to replace damaged tissues, e.g. in conditions such as:
Type 1 diabetes: insulin-producing pancreatic cells could be produced to replace damaged cells in the pancreas
Paralysis: healthy nerve cells could be used to repair damaged tissue in the nervous system
Adult stem cells can be cultured in the lab and encouraged to differentiate into some types of specialised cells
This type of treatment has already been used to replace faulty blood cells in sickle cell disease
Scientists are interested in extracting stem cells from embryos
These embryonic stem cells can then be encouraged to differentiate into most types of specialised cell
Such stem cell treatments could provide a wide variety of medical treatments
Some people have ethical concerns around the use of embryonic stem cells in medicine
Scientists hope to be able to use treatments involving tissue grown from a patient's own stem cells; this would avoid problems such as:
The need for tissue typing
A shortage of organ donors
Transplant rejection
Evaluating the use of stem cells in medicine
There are many benefits and risks associated with the use of stem cells in medicine, as well as considerable ethical and social concerns
Evaluating stem cells in medicine table
Benefits of using stem cells | Concerns around stem cell treatments | Social issues | Ethical issues |
|---|---|---|---|
Potential to treat a wide - variety of diseases Organs developed from a patient's own stem cells reduces the risk of organ rejection and the need to wait for an organ donor Adult stem cells are already used successfully in a variety of treatments | Stem cells cultured in the lab could become infected with a virus which could be transmitted to the patient There is a risk of cultured stem cells accumulating mutations and developing into cancer cells Low numbers of stem cell donors and difficulty in locating a good match between donors and patients | Stem cells can be collected before birth (from amniotic fluid) or after birth (umbilical cord blood) and stored by a clinic but this can be expensive and so isn't an option for everyone A lack of peer-reviewed clinical evidence of the success of stem cell treatment means that there is a level of distrust There is a lack of education available to explain what stem cells can and cannot be used for | Stem cells may be sourced from unused embryos produced in IVF treatment - is it right to use them? Who gives permission? Is it right to create embryos through therapeutic cloning and then destroy them? Who owns them? Should an embryo be treated as a person with human rights or as a commodity? |
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