Lesson 6 of 7 / Cells and stem cells
How many cell types can a stem cell make?
How is potency different from self-renewal?
In this lesson: Distinguish totipotent, pluripotent and multipotent stem cells using the required examples.
About 5 min
The key ideaStem cells can self-renew and generate differentiated cells. Potency describes the range of cell types they can produce.
Explore the idea
Compare the possible descendants
Can form the body and extraembryonic tissues needed for a complete organism. Green boxes show included ranges; pale boxes are outside that cell's normal potency.
Original schematic. Structures, cell numbers and distances are illustrative, not to scale.
Explanation
Self-renewal maintains a population of stem cells through division. Differentiation produces cells with specialised structures and functions. A stem cell can support both processes, but not every daughter cell must remain a stem cell.
A totipotent cell, such as a zygote in the syllabus example, can give rise to all the cell types needed for an organism, including extraembryonic tissues. This is the broadest of the three potency categories.
Embryonic stem cells are pluripotent: they can produce the body's many cell types but cannot, on their own, generate all the extraembryonic tissues required to form a complete organism. Blood stem cells are multipotent: they produce a related range of blood cell types.
Potency is a capability, not a claim that every cell type is produced at once. A blood stem cell can give rise to red cells and several white-cell lineages under suitable signals; it does not normally produce a nerve cell.
Step by step
- 1
Ask about renewal
Can divisions maintain the stem-cell population?
- 2
Ask about range
Does differentiation extend to all tissues, body cell types, or a restricted related group?
Worked example
A blood-cell lineage
A stem cell produces red blood cells and several types of white blood cell, but not neurons. Classify its potency.
One way to explain it
It is multipotent. It generates several related cell types within the blood system, rather than every body cell type.
Why this answer works
- More than one possible fate does not automatically mean pluripotent.
- Use the range of lineages, not their number alone.
Is this true? "Pluripotent and totipotent mean exactly the same thing."
Totipotency includes the extraembryonic tissues needed for a complete organism; pluripotency is the capacity to form the body's cell types.