2.2.4Structure & Functions in Living Organisms
Stem Cells in Medicine: Advantages and Disadvantages — Edexcel International GCSE Biology 4BI1 Revision Notes & Topical Questions
5 min read 4 parts Lesson 13 of 21 Unit quiz
Section 1 of 4Types of Stem Cell
Stem cells can divide by mitosis many times and may stay as stem cells or differentiate into specialised cells.
Embryonic
- Found only in embryos, and able to differentiate into any type of cell needed to build all the tissues and organs of the body.
Adult
- Found in some tissues such as bone marrow, and able to differentiate into only a limited range of cell types.
Bone marrow
- Adult stem cells here form red blood cells, white blood cells and the cells that make platelets, but not nerve or muscle cells.
| Feature | Embryonic stem cells | Adult stem cells |
|---|---|---|
| Source | Embryos | Some adult tissues and organs |
| Cell types possible | All types | A limited number |
| Ethical concern | Embryo is destroyed | Much smaller |
Section 2 of 4Uses in Medicine
Stem cell therapy aims to replace or repair cells that are not working properly.
Uses in Medicine
Blood disorders
- Healthy donor bone marrow can be transplanted so that the patient's marrow produces working blood cells.
Anaemia
- Replacement red blood cells improve the transport of oxygen around the body.
Immune deficiency
- New white blood cells such as lymphocytes and phagocytes can improve the body's defences against infection.
Clotting problems
- A supply of platelets helps treat patients whose blood does not clot properly.
Section 3 of 4Evaluating Stem Cell Therapy
Exam questions ask you to weigh benefits against risks and social concerns.
1
Advantage: embryonic stem cells could be used to make almost any cell type, giving the potential to treat many conditions.
2
Advantage: using the patient's own stem cells means the new cells carry the same antigens, so the body does not reject them.
3
Disadvantage: donor cells have different antigens, so the patient must take immunosuppressant drugs, which weaken the defence against infection.
4
Ethical issue: obtaining embryonic stem cells destroys an embryo, which some people regard as a potential human life.
5
Balance the points: say who benefits, who objects and why, then give a justified conclusion.
Section 4 of 4Exam Checklist & Tips
2.2.4 – Key Points for the Exam
- Stem cell An undifferentiated cell that can divide by mitosis and differentiate into other cell types.
- Embryonic stem cell A stem cell from an embryo that can become any cell type.
- Adult stem cell A stem cell from adult tissue that can become only a limited range of cell types.
- Antigen A protein on the surface of a cell that the immune system uses to recognise it as self or foreign.
- Immunosuppressant A drug that reduces the activity of the immune system to prevent rejection.
Common Mistakes
- Saying adult stem cells can become any cell; they are limited to a few types.
- Claiming embryonic stem cell use has no disadvantages; the ethical objection must be mentioned.
- Forgetting that donor cells carry different antigens and may be rejected.
- Describing stem cells as specialised; they are unspecialised until they differentiate.
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Cambridge 9700 AS Biology
Core Formula
Magnification Triangle & Unit Conversion
Formula: M = I / A ⇔ A = I / M ⇔ I = M × A
Units: 1 mm = 1,000 μm = 1,000,000 nm.
Rule: Convert Image size (ruler mm) to μm by ×1,000 before dividing by Actual size.