Stem Cells Flashcards
What is differentiation?
- the process of a cell becoming specialised
What is a stem cell?
- undifferentiated/unspecialised cell that can turn into any cell
What is an undifferentiated cell?
- not adapted to any particular function
- have potential to differentiate into one of the range of specialised cells
What problems can the division of stem cells cause?
- if they don’t divide fast enough tissues are not efficiently replaced leading to ageing
- if there is uncontrolled division they form masses of cells called tumours which can develop into cancers
What is potency?
- a stem cells ability to differentiate into different cell types
- greater number of cell types it can differentiate into the greater the potency
What is a totipotent stem cell?
- differentiate into any type of cell
- a fertilised egg, zygote and the 8 or 16 cells from first few mitotic divisions are totipotent cells
- also differentiate into extra-embryonic tissues like the amnion and umbilicus
What is a pluripotent stem cell?
- can form all tissue types but not whole organisms
- present in early embryos
What is a multipotent stem cell?
- only form a range of cells within a certain type of tissue
- haematopoetic stem cells in bone marrow is an example because they give rise to various types of blood cell
What is the benefit of being a multicellular organism?
- groups of cells with different functions working together as one unit can use resources more efficiently than single cells operating on their own
Where are blood cells derived from?
- stem cells in the bone marrow
How long do neutrophils live? How many do stem cells produce an hour?
- about 6 hours
- 1.6 billion per kg per hour (figure increase during infection)
What are the two main sources of animal stem cells?
- embryonic stem cells
- tissue (adult) stem cells
What potency is an embryonic stem cell?
- totipotent at early stage of embryo development
- after about 7 days a blastocyst (mass of cells) has formed and the cells are now pluripotent.
- remain pluripotent in the foetus until birth
What potency is an adult stem cell?
- multipotent, but growing evidence they can be artificially triggered to become pluripotent
How can adult stem cells be restored?
- specific areas like bone marrow
- umbilical cord
Where are plant stem cells found?
- in meristematic tissue
- tissue found wherever growth is so for example at the tips of roots and shoots
- also found between phloem and xylem tissues. This is called vascular cambium.
What diseases can stem cells be used to treat?
- heart disease (some success)
- type 1 diabetes (some success)
- Parkinson’s disease
- Alzheimer’s disease
- macular degeneration (early results encouraging)
- birth defects (some success)
- spinal injuries (some success)
How are Parkinson symptoms produced and does stem cell treatment work?
- shaking and rigidity caused by death of dopamine producing cells in the brain
- drugs currently only delay progress
What is Alzheimer’s and does stem cell treatment work?
- brain cells destroyed as a result of build up of abnormal proteins
- drugs only alleviate symptoms
How can stem cells be used to treat burns?
- they’re grown on biodegradable meshes and can produce new skin for burn patients
- quicker than taking graft from another part of the body
How can stem cells be used in drug trials?
- drugs can be tested on cultures of stem cells before on animals and humans
What are the objections of using stem cells from embryos?
- religious
- moral: life begins at conception and so destruction of embryo is murder, lack of consensus when embryo has rights and who owns the genetic material that is being used.
What is the disadvantage of using umbilical cords over embryonic stem cells?
- multipoint, not pluripotent so restricts use
What is the disadvantage of using adult stem cells?
- don’t divide as well as umbilical stem cells
- more likely to have acquired mutations
What are induced pluripotent stem cells?
- iPSCs
- adult stem cells genetically modified to act like embryonic stem cells and so are pluripotent.
Why is the use of stem cells called regenerative medicine?
- stem cells divide and specialise
- damaged tissue replaced
