6.5 Stem cells Flashcards
Define differentiation
The process of a cell becoming differentiated, involving the selective expression of genes in a cell’s genome.
Define undifferentiated
Unspecialised cell originating from meiosis or mitosis
Define stem cells
Undifferentiated cells wih the potential to differentiate into a variety of specialised cells
What are the main 3 roles of stem cells in the body?
Stem cells can repeatedly undergo cell division: Produce new cells for: - Growth - Development - Tissue repair
What phase of the cell cycle do specialised cells enter?
G0
Why do specialised cells enter G0?
Once a cell becomes specialised, it can no longer divide
Why do stem cells have to strictly controlled?
If stem cells don’t divide fast enough, tissues aren’t efficiently replaced which leads to ageing
What is the issue with stem cells dividing too fast?
Uncontrolled division can result in the formation of masses of cells - tumours - which can lead to cancer
Define the ‘potency’ of a stem cell.
A stem cell’s ability to differentiate into different types of cells
What happens if a stem cell loses its potency?
The stem cell can no longer specialise
What influences the potency of a stem cell?
The greater the number of cell types a stem cell can differentiate into, the greater its potency
What are the 3 types of cells stem cells can differentiate into?
- Totipotent
- Pluripotent
- Multipotent
What are the characteristics of totipotent cells?
- Can differentiate into any cell type
- Can differentiate into extra-embryonic tissues e.g. amnion and umbilicus
- Form the whole organism
Give examples of totipotent cells.
A fertilised egg/zygote and 8-16 cells from first few mitotic divisions
What are the characteristics of pluripotent cells?
- Can form all tissue types, but not whole organisms
- Origin of different tissue types within an organism
Where are pluripotent cells found?
Early embryos
What is the characteristic of multipotent cells?
Only form a range of cells within certain types of tissue
- Give an example of multipotent stem cells.
- Where are these found?
- Why are these stem cells multipotent?
- Haematopoetic stem cells
- Bone marrow
- They give rise to various types of blood cells
What are erythrocytes also known as?
Red blood cells
What are neutrophils also known as?
White blood cells
Where are all blood cells derived from?
Stem cells in bone marrow
Why do mammalian erythrocytes need to be regularly replaced?
They have a short lifespan of 120 days.
Why do mammalian erythrocytes have a short lifespan?
Mammalian erythrocytes have a short lifespan due to their lack of nucleus and organelles - erythrocytes transport oxygen + maximise oxygen-carrying capacity by having less organelles to have more room for more haemoglobin.
How long do neutrophils live?
6 hours
What are the 2 main sources of animal stem cells?
- Embryonic stem cells
2. Tissue (adult) stem cells
Define meristematic tissue
Tissue containing stem cells found at regions of growth in plants
Where can meristems be found?
Tips of root, shoots and between phloem and xylem tissue
What is the vascular cambium?
Meristematic tissue sandwiched between the phloem and xylem
What do cells from the vascular cambium differentiate into?
Different cells present in xylem and phloem tissue.
In this way, vascular tissue grows as the plant grows
What type of stem cell are meristems?
Pluripotent
Why are stem cells be used to treat heart disease?
After a heart attack, cardiac muscle tissue in the heart is damaged, usually irreparably.
Why are stem cells used to treat type 1 diabetes?
The body’s own immune system destroys insulin-producing cells
Why are stem cells used to treat Parkinson’s disease?
Symptoms are caused by the death of dopamine-producing cells.
Drugs delay onset of the disease.
Why are stem cells used to treat Alzheimer’s disease?
Brain cells are destroyed as a result of buildup of abnormal protein.
Drugs alleviate symptoms.
Why are stem cells used to treat macular degeneration?
Macular degeneration causes blindess in elderly and diabetics.
Why are stem cells used to treat birth defects?
Some birth defects have been reversed in mice
Why are stem cells used to treat spinal injuries?
Some movement has been restored in hind limbs of rats with spinal injuries
What are the 7 diseases stem cells can be used to treat?
Heart disease Type 1 diabetes Parkinson's disease Alzheimer's disease Macular degeneration Birth defects Spinal injuries
What 3 other areas are stem cells used for?
Treatment of burns
Drug trials
Developmental biology
How are stem cells used to treat burns?
Stem cells grown on biodegradable mesh can produce new skin for burn patients,
This is faster than grafting.
