Stem Cells

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CognitoStem cells — types and uses

Key facts & methods

What are stem cells?

Stem cells: undifferentiated cells that can divide and differentiate into specialised cell types.
Embryonic stem cells: from early embryos (blastocyst). Can differentiate into any cell type — totipotent/pluripotent.
Adult stem cells: found in specific tissues (e.g. bone marrow). Can only differentiate into related cell types — multipotent. E.g. bone marrow stem cells → blood cells.
Meristems in plants: regions of undifferentiated cells that can differentiate into any plant cell type.

Medical uses of stem cells

Bone marrow transplants: adult stem cells replace damaged blood cells (e.g. in leukaemia).
Therapeutic cloning: patient's nucleus inserted into empty egg cell → stem cells grown → used to replace damaged tissue.
Advantage of therapeutic cloning: cells are genetically identical to patient → no rejection.
Potential future uses: treating Parkinson's, diabetes (replace insulin-producing cells), spinal injury.
Risk: stem cells could become cancerous if they divide uncontrollably.

Ethical considerations

Embryonic stem cells: require destruction of a human embryo — ethical debate about moral status of embryo.
Some argue: embryo has full human status → using it for research is wrong.
Others argue: embryo has potential to relieve great suffering → benefits outweigh concerns.
Compromise: use unused embryos from IVF treatment that would otherwise be destroyed.
Adult stem cells: fewer ethical issues but more limited differentiation ability.

Plant meristems (contrast)

Meristems found at tips of roots and shoots.
Cells in meristems are undifferentiated and can differentiate into any plant cell.
Advantage for agriculture: cloning plants from meristematic cells produces many identical plants quickly.
Plant stem cell technology less ethically controversial than human embryonic stem cells.

Exam questions — 5 questions · 11 marks · AQA 8461 style

1 markEmbryonic vs adultAQA 8461 style

What is the key difference between embryonic and adult stem cells?

A Adult stem cells can differentiate into more cell types than embryonic stem cells

B Embryonic stem cells can differentiate into any cell type; adult stem cells can only differentiate into related cell types

C Only embryonic stem cells are found in humans

D Adult stem cells divide faster than embryonic stem cells

4 marksTherapeutic cloningAQA 8461 style

Describe how therapeutic cloning could be used to treat a patient with a damaged liver, and explain one advantage of this approach over using donor tissue. (4 marks)

Hint: Step-by-step: source of nucleus → into egg → embryo forms → stem cells extracted → differentiate → transplant. Advantage = no rejection.

+40 XP

1 markEthical issueAQA 8461 style

What is the main ethical concern about using embryonic stem cells?

A They may not differentiate into the correct cell type

B The embryo is destroyed to obtain the stem cells, raising questions about its moral status as a potential human life

C Embryonic stem cells always cause cancer

D Adult stem cells are more effective so embryonic stem cells should not be used

3 marksBone marrow transplantAQA 8461 style

Explain how a bone marrow transplant can treat a patient with leukaemia. (3 marks)

Hint: Explain what leukaemia does, what the transplant provides, and the outcome.

+30 XP

1 markPlant stem cellsAQA 8461 style

Where in plants are the equivalent of stem cells found?

A In the leaves

B In the phloem

C In meristems at the tips of roots and shoots

D In the xylem

What are stem cells?

Medical uses of stem cells

Ethical considerations

Plant meristems (contrast)

Module complete! 🎉