Stem Cells

Question 1

Totipotent cells

Answer 1

have ability to differentiate into any cell type to form whole organisms and so are also pluripotent and multipotent

e. g. Zygotic stem cells
- zygote cell is created when a single celled sperm and egg unite
- this totipotent fertilised egg has the potential to give rise to all the cell types and placental cells in an organism
- more totipotent cells are produced during the early cell divisions in embryonic development

Question 2

Pluripotent cells

Answer 2

have ability to differentiate into almost any cell type to form any organ and so are not totipotent but are multipotent

e. g. Embryonic stem cells (ES cells)
- derived from blastocysts
- can give rise to all specialised cells in the body (but not placental or umbilical cord)
- blastocyst is a hollow ball of cell, filled with fluid, that forms about four days after fertilisation from the zygote, and prior to implantation

Question 3

Multipotent cells

Answer 3

have ability to differentiate into a limited range of cell type and so are not pluripotent or totipotent

e. g. Blood stem cells
- primary role: to maintain and repair tissue by replacing aged cells and those that are lost through normal wear and tear
- have the potential to either remain as stem cells or develop into another different cell type with a more specialised function, such as a muscle, a red blood cell, or a brain cell in the body
- unspecialised cells that can differentiate into more than one cell type but are more limited than pluripotent cells

Question 4

Stem cell

Answer 4

a relatively unspecialized cell that can give rise to one or more types of specialized cells
- Have the unique ability to self-renew or to differentiate into various cell types in response to appropriate signals within body → provide stem cells with unique capabilities for tissue repair, replacement and regeneration

Question 5

Features

Answer 5

1. Unlimited self-renewal capabilities
   - Able to continually divide and reproduce themselves for long periods
   - When cells replicate themselves many times over, it is called proliferation
2. Non-differentiated cells with unspecialized functions
   - Do not have any tissue-specific structures that allow it to perform specialized functions
3. Can differentiate into specific cell types under appropriate conditions
   - e.g. Stem cells in bone marrow differentiate to all the different kinds of blood cells
   - e.g. Stem cells in the adult brain continue to produce certain kinds of nerve cells