Cells and organisation · GCSE Biology
Stem cells
Compare embryonic, adult and meristem stem cells for GCSE Biology: unspecialised cells that can differentiate, bone-marrow treatments, therapeutic cloning, and the ethics examiners expect.
A stem cell is unspecialised and can still become other cell types. Embryonic: any cell. Adult (for example bone marrow): limited range. Plant meristem: any plant tissue, for life.
The important bits
What you need to know
- 1
A stem cell is an unspecialised cell that can divide (by mitosis) and differentiate into specialised cells.
- 2
Embryonic stem cells come from an early embryo and can become any human cell type (pluripotent). That makes them medically useful and ethically controversial.
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Adult stem cells are found in tissues such as bone marrow. They can become a limited range (for example red blood cells, white blood cells, platelets). Bone-marrow transplants already treat some blood disorders and leukaemia.
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Plant meristems in shoot and root tips contain stem cells that can differentiate into any plant tissue throughout life. That is why cuttings and tissue culture can clone plants.
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Possible uses: replace damaged cells in paralysis, diabetes (insulin-producing cells), or heart disease. Many of these uses are still developing; bone-marrow treatment is established.
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Therapeutic cloning: a patient’s nucleus is placed in an enucleated egg, the embryo’s stem cells match the patient’s genes, so rejection is less likely. It still involves creating and using an embryo.
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Risks: viral infection from cultured cells, the chance that transplanted cells divide uncontrollably (tumour), and immune rejection if the cells are not a genetic match.
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Ethical objections: using or destroying embryos, “playing God”, religious views on when life begins. Evaluation answers need a biological use, a risk or ethical point, and a conclusion.
Quotations worth analysing
Short evidence. Real method.
“Stem cells are unspecialised cells that can differentiate into specialised cells.”
Unspecialised plus differentiate. “They can turn into anything” is only true of embryonic, not adult, stem cells.
“Embryonic stem cells can become any cell type; adult stem cells can become only a limited number of types.”
This contrast is the most common four-mark. Plant meristems stay flexible for life, unlike most animal cells.
“Bone marrow contains adult stem cells that can form blood cells.”
Use this when the question wants a treatment that already works, not a hypothetical spinal repair.
Go deeper
How do I evaluate embryonic stem cells without preaching?
Give a biological advantage: they can differentiate into any cell type, so in principle they could replace neurones, pancreatic cells or heart muscle. Give a practical advantage of therapeutic cloning: a genetic match reduces rejection. Give a risk: cultured cells may carry viruses, or may form tumours if mitosis is not controlled. Give an ethical objection: the embryo is destroyed, and some people believe that is ending a human life. Then a conclusion that uses the biology, for example “bone-marrow adult stem cells already treat leukaemia without embryos, so they are preferable where they work, but they cannot yet make every tissue”. “It is wrong” or “it is amazing” with no mechanism scores poorly. The mark scheme wants both sides and a judgement.
Go deeper
Why can a plant cutting grow a whole plant when a human skin cell cannot?
Meristem stem cells remain able to differentiate into xylem, phloem, root, leaf and flower tissue throughout the plant’s life. A cutting that includes meristematic tissue (or can form it) therefore rebuilds missing organs. Most human cells are terminally differentiated: a skin cell’s fate is sealed, even though it still has the whole genome. Only embryonic cells (and a few adult stem-cell niches) keep wide potential. Cloning plants by tissue culture uses this flexibility on a large scale, with hormone ratios steering root versus shoot. In the exam, “plants have stem cells in meristems that can become any tissue” is the sentence. Do not write that animal stem cells are only in embryos — bone marrow is the counter-example.
Go deeper
What does differentiation actually mean at GCSE?
The cell keeps the same genes but only expresses (switches on) the genes needed for its job. A palisade cell expresses chlorophyll genes; a root hair does not. Stem cells have not yet locked that pattern, so they can still go down different pathways. Mitosis of a stem cell can produce another stem cell (self-renewal) plus a daughter that specialises. That is how bone marrow keeps supplying blood cells for decades. Cancer can be thought of as differentiation and cycle control going wrong, but do not call a tumour a stem cell unless the paper does. If asked why cloned plants are genetically identical, the answer is mitosis from meristem cells of one parent, not meiosis and fertilisation.
See the idea in action
A patient with leukaemia receives a bone-marrow transplant. Bone marrow contains adult stem cells that divide by mitosis and differentiate into healthy white blood cells. The donor must be a close match to reduce rejection. This treatment already exists. Using embryonic stem cells to repair a spinal cord is still largely experimental: those cells can become any type, including neurones, but the embryo is used and there is a risk of uncontrolled division. An evaluation should state both the medical potential and the ethical or safety issue, then judge.
Exam technique
Turn knowledge into marks
Define unspecialised then differentiate. Contrast embryonic (any type) with adult (limited) and meristem (any plant tissue). In evaluate questions, give one use, one risk or ethical objection, and a conclusion. Do not confuse stem cells with gametes.
Common mistakes
Do not give these marks away
- 01
Writing that adult stem cells can become any cell type.
- 02
Giving only an ethical opinion on embryos with no biological use or risk.
- 03
Saying stem cells are produced by meiosis, or that meristems exist in animals.
What is the main difference between embryonic and adult stem cells?
AEmbryonic stem cells can become any cell type; adult stem cells can become only a limited range
BAdult stem cells can become any cell type; embryonic stem cells cannot divide
CBoth can only become red blood cells
DEmbryonic stem cells are found in meristems
Show the answer
Embryonic stem cells can become any cell type; adult stem cells can become only a limited range. Embryonic cells are the most flexible. Adult stem cells, such as those in bone marrow, are already restricted. Meristems are plant tissues.
Quick questions
If this is the bit you searched
What is a stem cell GCSE Biology?
An unspecialised cell that can divide and differentiate into specialised cells. Embryonic stem cells can become any type; adult stem cells are more limited.
Where are stem cells found in plants?
In meristems, especially shoot and root tips. They can differentiate into any plant tissue throughout the plant’s life.
How are stem cells used to treat leukaemia?
A bone-marrow transplant supplies adult stem cells that can divide and specialise into healthy blood cells.
What is therapeutic cloning?
An embryo is made with the patient’s genes so that stem cells taken from it are a genetic match and less likely to be rejected.