Stem cells Flashcards
(19 cards)
Define what a stem cell is.
A stem cell is a cell that can divide (by mitosis) an unlimited number of times and has the potential to remain a stem cell or to develop into a specialised cell.
What are the properties of stem cells?
Stem cells have the capacity to divide endlessly and differentiate along different pathways.
What is cell differentiation?
Cell differentiation is the development of unspecialised cells (following fertilisation) into specialised cells.
What is the importance of the stem cell niche?
The stem cell niche can maintain cells or promote their proliferation and differentiation.
Outline the location and function of two types of multipotent stem cells in an adult human body.
Bone marrow:
Haemopoietic stem cells are located within the bone marrow and give rise to the different types of blood cells (e.g. erythrocytes, leucocytes and thrombocytes
Bone marrow transplants are commonly employed to replace the haemopoietic stem cell niche following chemotherapy for leukemia (blood cell cancer)
Hair Follicles
The hair follicles contain a range of epidermal stem cells that are involved in cyclic bouts of hair growth, skin innervation, vascularisation and wound repair
These stem cells could potentially be harvested and used to regenerate skin tissue in burns victims (or stimulated to promote hair regrowth in bald individuals)
What is meant by totipotency in stem cells?
Totipotent stem cells are stem cells that can differentiate into any cell type found in an embryo and can become cells that make the placenta.
What are pluripotent stem cells?
Pluripotent stem cells are embryonic stem cells that can differentiate into any cell type found in an embryo but are not able to differentiate into the cells of the placenta.
What type of stem cells are those found in cells in early-stage animal embryos?
Cells in early-stage animal embryos are totipotent.
How can a surface area to volume relationship be modelled? (NOS)
Surface area to volume relationship can be modelled using cubes of different side lengths.
Compare cell surface area with cell volume in relation to the exchange of materials.
The exchange of materials across a cell surface depends on its surface area whereas the need for exchange depends on cell volume.
How is the size of male gametes (sperm cells) adapted to their function?
Male gametes are long and narrow to allow for streamlined movement/swimming toward the egg.
How is the size of red blood cells adapted to carry out their function?
Red blood cells are small to allow movement through narrow capillaries.
How is the size of muscle cells adapted for their function?
Muscle cells are larger than normal cells, and their longer length and diameter are designed to exert force during muscle contraction.
What is the role of grandients in gene expression?
Gradients of signaling molecules (morphogens) diffuse through the embryo, creating varying concentrations in different regions.
A cell’s location within the embryo (based on morphogen concentration) determines which genes are activated, influencing cell fate.
How unspecialized cells become specialized?
Fertilization is when a sperm cell fuses with an egg cell to form a zygote, which contains the entire genetic blueprintfor a new organism.
The zygote undergoes multiple rounds of mitosis, creating a cluster of genetically identical cells.
Early embryonic cells are totipotent, meaning they can become any cell type in the organism or the extra-embryonic tissues (e.g., placenta).
Cells then transition to pluripotent stem cells, which can form any cell type within the organism but not extra-embryonic structures.
Define stem cell niche.
A stem cell niche is a microenvironment within a tissue that supports stem cells by maintaining their self-renewal, survival, and differentiation potential.
Define totipotent, multipotent and pluripotent.
There are three main types of stem cells present at various stages of human development:
Totipotent – Can form any cell type and develop into entirely new organisms
Pluripotent – Can form any cell type arising from the three germ layers
Multipotent – Can only form a number of closely related cell types
Describe the relationship between cell size and the SA:V ratio of the cell.
As a cell increases in size, its volume increases faster than its surface area, leading to a lower surface-area-to-volume ratio.
Surface Area: Larger surface area allows for more material to be transported into or out of the cell.
Volume: The cell’s internal volume dictates how much material (like nutrients or waste) needs to be exchanged.
Explain the limitations imposed by SA:V ratio.
Diffusion Rates: Essential molecules like oxygen and glucose take longer to diffuse through larger cells.
Metabolic Demands: Larger cells have more volume, which increases their demand for nutrients and produces more waste.
Structural Challenges: Large cells might require additional support structures that reduce the effective surface area available for exchange.
