stem cells Flashcards
What is a stem cell? (1)
An undifferentiated cell that has the potential to form different types of cells
What is potency in stem cells? (1)
Stem cell’s ability to differentiate into different cell types
What are totipotent stem cells? (2)
Stem cells that can develop into any type of body cell, including extra-embryonic tissue
Found in the early embryo (first 4 days post-fertilisation), e.g., zygote
What are pluripotent stem cells? (2)
Stem cells that can develop into any body cell except extra-embryonic cells (e.g., placenta)
Present in early embryos, and can form all tissue types but not whole organisms
What are multipotent stem cells? (2)
Stem cells that can differentiate into a limited number of cell types
E.g., haematopoietic stem cells in bone marrow give rise to various blood cells
What are unipotent stem cells? (2)
Stem cells that can only differentiate into one cell type
E.g., unipotent stem cells in the heart can replace damaged cardiomyocytes
How are stem cells used in animals? (1)
Replace damaged cells, e.g., new skin cells
How are stem cells used in plants? (2)
Plants grow continuously
So stem cells are needed to produce new shoots and roots throughout their life
Why can a skin cell produce keratin but not myosin, and a muscle cell produce myosin but not keratin? (3)
In skin cells, the gene for keratin is expressed,
While the gene for myosin is inactive.
In muscle cells, the opposite is true
Why do skin cells retain the ability to divide, while cells in some other organs do not? (2)
Skin cells are prone to wear and tear, requiring frequent replacement
Other organs experience less damage and need fewer new cells
How are erythrocytes derived from stem cells? (2)
Erythrocytes lack a nucleus and organelles, giving them a short lifespan (about 120 days).
Adult stem cells in the bone marrow divide and differentiate to replace worn-out erythrocytes.
How are neutrophils derived from stem cells? (2)
Neutrophils have a very short lifespan (around 6 hours)
Adult stem cells in the bone marrow divide and differentiate to replace worn-out neutrophils
How are xylem vessels and phloem sieve tubes produced in plants? (2)
Stem cells in the vascular bundle (a type of meristem)
Divide and differentiate to become xylem vessels and phloem sieve tubes
How could stem cells be used to treat neural diseases? (2)
Can be used to regrow healthy nerve cells
Replacing those that die in e.g. Alzheimer’s, which causes memory loss
How are stem cells used in developmental biology? (1)
Stem cells’ ability to divide indefinitely and differentiate
Makes them useful for studying how organisms grow and develop
What are some positives of using stem cells in research? (2)
- Stem cell therapies could save lives, e.g., by preventing people from dying while waiting for an organ transplant
- They can improve the quality of life, e.g., by restoring sight for blind individuals
What are some negatives of using stem cells in research? (3)
- Obtaining embryonic stem cells involves destroying an embryo, which some people believe is unethical.
- Some believe that embryos have a right to life, and using them for stem cell research is morally wrong.
- Others argue that only adult stem cells should be used, although they are not as flexible as embryonic stem cells.
