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2.1.3Unit 2 — Multicellular Organisms

Stem Cells — SQA National 5 Biology Revision Notes & Topical Questions

5 min read 4 parts Lesson 3 of 39

📚 SQA National 5 Biology Hub / Topical Revision
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Section 1 of 4Differentiation

2.1.3 Stem Cells
Unspecialised
  • Stem cells are unspecialised cells that can divide to make more cells of the same type.
Differentiation
  • The process by which a cell becomes specialised, switching on only some of its genes.
Specialised
  • Cells such as nerve, muscle and red blood cells have a special structure for their specific job.
Plants
  • In plants, stem cells are found in the meristems, at the tips of roots and shoots.

Section 2 of 4Types of Stem Cell

Types of Stem Cell
Embryonic
  • These come from early embryos and can differentiate into any type of cell in the body.
Tissue
  • These are found in tissues such as bone marrow and can form only a limited range of cell types.
Replacement
  • Tissue stem cells replace worn-out or damaged cells, such as blood or skin cells.
Meristem
  • Plant meristem cells can differentiate into many types of plant cell throughout life.
FeatureEmbryonicTissue
SourceEarly embryoAdult tissues
Can formAny cell typeLimited range

Section 3 of 4Uses and Issues

1
Stem cells could be used to repair damaged tissue, for example in therapies for some diseases and injuries.
2
Bone marrow stem cells already treat some blood disorders.
3
Researchers use stem cells to study how cells become specialised and to test new drugs.
4
Ethical issues arise because obtaining embryonic stem cells involves the destruction of an embryo.
5
Some people believe the benefits outweigh the concerns, while others oppose the research.

Section 4 of 4Exam Checklist & Tips

2.1.3 – Key Points for the Exam

  • Stem cell An unspecialised cell that can divide and differentiate.
  • Differentiation Becoming a specialised cell type.
  • Meristem A region in plants where stem cells divide.
  • Embryonic stem cell A stem cell from an early embryo that can become any cell type.
  • Tissue stem cell A stem cell in adult tissue with a limited range.

Common Mistakes

  • Saying that stem cells have no genes; they have all the genes.
  • Mixing up embryonic and tissue stem cells.
  • Writing that plants have no stem cells; they are in the meristems.
  • Giving only ethical arguments for or against, instead of balanced points.

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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.