B2.1 Supplying the Cell - Differentiation & Stem cells Flashcards
2.1.5 Differentiation 2.1.6 Stem cells
What is differentiation?
Process by which stem cells become specialised into different types of cells
What is produced once a sperm cell enters an egg?
Zygote
By what process does a zygote divide?
Mitosis
The zygote is composed of what type of cells?
Stem cells
When does a zygote become an embryo?
3-5 days after fertilisation
How do the cells of a zygote differ from an organisms somatic cells?
They are unspecialised and can therefore differentiate into any type of specialised cell.
Where are stem cells found in animals?
Embryos - Embryonic stem cells Brain, bone marrow, skin, liver - Adult stem cells N.B Multipluripotent stem cells have also now been isolated in the umbilical cord
Where are stem cells found in plants?
The meristems - unspecialised cells found in the root tips, shoot tips and in rings around the stem
How do the cells in the meristem differ from normal plant cells?
Differentiated plant cells cannot divide as they have thick & rigid cell walls Meristem cells are much smaller, have thin walls, small vacuoles and no chloroplasts
State a key difference between specialised plant and animal cells?
Once differentiated animal cells can only divide to produce that specialised cells. Plant cells however, under the right conditions, can become unspecialised and then re-specialise in order to adapt to their environment.
Name 5 types of specialised cells that a stem cell could differentiate into.
Animal
- Gamete e.g sperm cell, ovum
- Muscle cell
- Adipocyte cell
- Osteoblast
- Blood cell e.g erythrocyte, neutrophils
- Nerve cell
- Cilliate epithelial cell
- Goblet cell
Plant
- Palisade cells
- Root hair cell
- Guard cell
How is a red blood cell specialised for its role?
- Biconcave discs - increases surface area
- Haemoglobin - binds to and releases oxygen
- Enucleated - more room for oxygen transport
How is sperm cell is specialised to transfer genetic material?
- Flagellum - movement
- Mitochondria - provide energy for movement
- Acrosome - contains digestive enzymes to allow breakdown the outer membrane of ovum
How is an adipocyte specialised for its role?
- Can expand to 1000 times original size
- Small layer of cytoplasm
- Fat reservoir.
What is the function of a goblet cell?
Produces mucus to trap dust mucus and bacteria which the cillia then waft back up the throat to be swallowed.
How are palisade cells adapted for their function?
- regularly shaped - can be closely packed cells that form a continuous layer at the top of the leaf
- Large surface area - able to absorb more light for photosynthesis
- Packed with chloroplasts - for photosynthesis
How are guard cells adapted for their function?
- Surround the stoma and regulate the rate of transpiration and CO2 uptake.
- Inner wall thicker causing the ‘bean-like’ shape and gap when turgid
- Open to allow exchange
- Close to prevent exchange
What type of cells can adult stem cells differenetiate into?
Only into cells from the type of tissue where they are found.
Why are adult stem cells not as useful for medical research?
They only differentiate into a narrow range of cell types
What are embryonic stem cells and why are they more useful to stem cell research?
- Cells taken from 3-5 day old zygotes
- Thye can specialise into any type of specialised cells
- Potential to cure and treat disease
Why are embryonic stem cells controversial?
Embryos are killed to obtain the cells.
What are induced-pluripotent stem cells and how may they be useful?
- Adult somatic cells altered to have properties of embryonic stem cells
- May allow use of reprogrammed cells instead of embryonic stem cells
- Solution to immune system rejection of ‘foreign’ stem cells
How are root hair cells adapted for their function?
