Lesson 6 of 7 / Cells and stem cells
How many cell types can a stem cell make?
How is potency different from self-renewal?
I can distinguish totipotent, pluripotent and multipotent stem cells using the required examples.
I can distinguish stem-cell features and toti-, pluri- and multipotency.Syllabus
Syllabus 8876, Core 1(p). Distinguish stem-cell features and toti-, pluri- and multipotency.
About 5 min
Make a guess. You are not marked.
A blood stem cell makes red cells, white cells and platelets. Can it make a nerve cell?
Show the answer
It is multipotent, limited to blood types.
Multipotent stem cells form related cell types within one lineage. Blood stem cells make blood cells.
The key idea
Stem 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.
Watch out for this
A student says: "Pluripotent and totipotent mean exactly the same thing." What is wrong with this?
Show the answer
Totipotency includes the extraembryonic tissues needed for a complete organism; pluripotency is the capacity to form the body's cell types.
Check your understanding
Which statement correctly describes a blood stem cell?
Show the answer
It can self-renew and generate several related blood-cell types.
This combines self-renewal with multipotency.
Exam-style questions
Check your understanding
Which statements are correct? 1: A zygote is totipotent. 2: Embryonic stem cells can form the placenta. 3: Blood stem cells are multipotent. 4: All stem cells can self-renew.
Show the answer
1, 3 and 4 only
The zygote is totipotent, blood stem cells are multipotent and all stem cells self-renew. Pluripotent embryonic stem cells do not form the placenta.
Quick recall
How is potency different from self-renewal?