3.2.9Unit 3: Practical Skills in Biology I
Stem Cells and Cell Potency — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 4 parts Lesson 23 of 27 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 4Stem Cells and Potency
A stem cell can divide by mitosis without limit, and its daughter cells may stay as stem cells or differentiate.
Potency
- Potency The range of specialised cell types a stem cell is able to become through differentiation.
Totipotent
- Totipotent Can form any cell type in the embryo and also the extra-embryonic cells of the placenta;
- found in the zygote and the first few cell divisions.
Pluripotent
- Pluripotent Can form any cell type of the embryo but not placenta cells;
- found in the inner cell mass of the blastocyst.
Multipotent
- Multipotent Adult stem cells able to form only a limited range of cell types, such as bone marrow cells making blood cells.
| Type | Source | Can become |
|---|---|---|
| Totipotent | Zygote, early embryo (about day 1-4) | Any cell, including placenta |
| Pluripotent | Inner cell mass of blastocyst (about day 5) | Any embryo cell, not placenta |
| Multipotent | Adult tissues such as bone marrow | A limited range of cells |
Section 2 of 4Uses in Medicine
Uses in Medicine
Leukaemia treatment
- Leukaemia treatment Diseased bone marrow is destroyed and replaced using a transplant of healthy stem cells that rebuild blood cell production.
Research targets
- Research targets Therapies are being researched to replace damaged nerve tissue after spinal injury and heart tissue after a heart attack.
Embryonic source
- Embryonic source These cells can form almost any tissue, but are taken from embryos, often spare ones left over from IVF.
Adult source
- Adult source Stem cells from bone marrow or brain are less versatile but can be donated with the permission of the donor.
Section 3 of 4Evaluating Stem Cell Use
Society must weigh benefits against ethical objections when deciding how stem cells may be used.
1
Embryonic cells have the greatest potential because they can become many tissue types, which could treat many diseases.
2
Many people object because collecting them destroys an embryo that could have developed into a person.
3
Adult stem cells raise fewer ethical issues but cannot form every cell type, so they cannot treat every condition.
4
Donor cells must be a close match in blood group and antigens, otherwise the patient immune system may reject them.
5
Regulatory authorities review research proposals, license and monitor centres, and issue codes of practice so the work is controlled.
Section 4 of 4Exam Checklist & Tips
3.2.9 – Key Points for the Exam
- Stem cell A cell that can divide by mitosis indefinitely and differentiate into specialised cells.
- Differentiation The process by which a cell becomes specialised for a particular function.
- Totipotent Able to become any cell type, including extra-embryonic cells.
- Pluripotent Able to become any cell type of the embryo but not placental cells.
- Multipotent Able to become only a limited range of related cell types.
Common Mistakes
- Saying that pluripotent cells can form the placenta, when only totipotent cells can form extra-embryonic tissue.
- Stating that adult stem cells cannot divide;
- they can divide many times but only make a limited range of cell types.
- Giving only a one-sided answer to an evaluation question, when both benefits and ethical objections are required.
- Describing stem cells as already specialised; they are unspecialised until they differentiate.
Last updated:
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.