Free Stem Cells revision notes for OCR A Level Biology – covering specification points 2.1.6(m) and 2.1.6(j).
Stem Cells
Stem cells are unspecialised cells that can divide and differentiate by expressing different genes when needed.
Stem cells are important because they give rise to new cells, allowing an organism to grow, replace dead or damaged cells (repair tissues) and (in some organisms) enable asexual reproduction.
Mitosis is done by stem cells, which is why they share those three important roles.
Potency
Potency is the number of types of cells a stem cell can give rise to (differentiate into).
The main types of stem cell potency are outlined in the table below:
| Potency | What it can become | Example |
|---|---|---|
| Totipotent | All body + placental cells | Zygote |
| Pluripotent | All body cells | Embryonic stem cells |
| Multipotent | A range of related cell types | Bone marrow stem cells |
| Unipotent | One specific type only | Skin stem cells |
A zygote (fertilised egg cell) is totipotent and can become all types of cells, because it can express all of its genes.
Other types of (animal) stem cells cannot differentiate into as many types of cells because some of their genes will be permanently turned off (or on).
Uses of Stem Cells
Stem cells have enormous potential in the field of medicine; a select few are described in the table below:
| Application | Description |
|---|---|
| Tissue Repair | Treat damaged cartilage, skin and cardiac tissue |
| Neurological Therapy |
For replacing damaged neurones/nerve tissue: • Spinal injuries • Parkinson’s • Alzheimer’s |
| Developmental Biology | Helps understand differentiation, signalling and regeneration |
