3. Stem Cells & Differentiation Flashcards
(35 cards)
1
Q
Multicellular organisms are made up from…
A
many different cell types that are specialised for their function
2
Q
What are stem cells
A
- Undifferentiated cells - meaning they are not yet ‘committed’ to a particularly cell ‘fate’: they have the potential to differentiate into any cell type.
- Once cells differentiate & become specialised, they lose the ability to divide (enter the G0 phase).
3
Q
Where are stem cells found
A
- All multicellular organisms have some form of stem cell.
- In HUMANS, stem cells are found in early embryos & in a few places in adults. Stem cells in early embryos can develop into ANY type of human cell. Stem cells in adults can only develop into a limited range of cells.
4
Q
What is differentiation
A
- Stem cells divide to become new cells, which then become specialised.
- Process by which a cell becomes specialised for its job is differentiation
5
Q
Use of stem cells in ANIMALS
A
Adult stem cells are used to replace damaged cells, eg. to make new skin or blood cells
6
Q
Use of stem cells in PLANTS
A
- Plants are always growing, so stem cells needed to make new shoots & roots throughout their lives.
- Stem cells in plants can differentiate into various plant tissue including xylem & phloem
7
Q
What else can stem cells do
A
Also able to divide to produce more undifferentiated stem cells (can renew themselves)
8
Q
Stem cells in bone marrow
A
- Cells in bone marrow differentiate into blood cells.
- Bones are living organs, containing nerves & blood vessels.
- Main bones have marrow in centres.
- Here, adult stem cells divide & differentiate to replace worn out blood cells - erythrocytes (RBCs) & neutrophils (WBCs).
9
Q
Stem cells in meristems
A
- Cells in meristems differentiate into xylem & phloem.
- In plants, stem cells are found in meristem (parts of plant where growth can take place).
- In root & stem, stem cells of the vascular cambium divide & differentiate to become xylem vessels & phloem sieve tubes.
10
Q
What do scientists believe about stem cells
A
- Believe they can be used to repair/replace damaged tissues in range of diseases. (eg. may be possible to use stem cells to treat neurological disorders caused by damage to nerve cells in brain).
- Used by scientists researching developmental biology - how organisms grow/develop. Studying stem cells can help understand more abt developmental disorder & cancer.
11
Q
5 specialised animal cells
A
- Neutrophils
- Erythrocytes
- Ciliated epithelial cells
- Squamous epithelial cells
- Sperm cells
12
Q
How are Neutrophils specialised for their functions
A
- (a type of WBC - play essential role in immune system/defend against disease)
- Flexible shape –> to engulf foreign pathogens
- Many lysosomes containing digestive enzymes in their granular cytoplasm –> to break down engulfed pathogens
- Have a characteristic multi-lobed nucleus –> makes it easier for them to squeeze through small gaps to get to the site of infections
13
Q
See pg65 & goodnotes for diagram of neutrophils
A
including slide micrograph
14
Q
How are Erythrocytes specialised for their functions
A
- (RBCs)
- Flattened biconcave disc shape –> increases SA:V - essential to their role of transporting oxygen around body
- NO nucleus or many other organelles –> more space for Hb
- Flexible –> to squeeze through narrow capillaries
15
Q
See pg65 & goodnotes for diagram of erythrocytes
A
+ slide micro
16
Q
How are Ciliated epithelial cells specialised for their functions
A
- (cover surfaces of organs)
- Hair-like structures called cilia (in ciliated epithelia, eg in airways) –> beat to waft mucus & particles away
- Goblet cells –> secrete mucus to trap unwanted particles in air, prevents bacteria from reaching alveoli once inside lungs.
17
Q
See pg65 & goodnotes for diagram of ciliated epithelial cells
A
+ slide micro
18
Q
How are Ciliated squamous cells specialised for their functions
A
- (forms the lining of the lungs & allows rapid diffusion of oxygen into blood)
- Made up of specialised squamous epithelial cells, flat & thin, only one cell thick –> rapid diffusion
19
Q
See goodnotes for diagram of ciliated squamous cells
A
+ slide micro
20
Q
How are Sperm cells specialised for their functions
A
- (male gametes/sex cells)
- Have flagellum –> movement to the ovum (egg) (female gamete)
- Lots of mitochondria –> provide energy to swim
- Acrosome contains digestive enzymes –> digest protective layers around the ovum, allowing sperm to penetrate, leading to fertilisation
21
Q
See pg65 & goodnotes for diagram of sperm cells
A
+ slide micro
22
Q
3 specialised plant cells
A
- Palisade mesophyll cells
- Root hair cells
- Guard cells
23
Q
How are Palisade mesophyll cells specialised for their functions
A
- (present in mesophyll, do most of the photosynthesis)
- Many chloroplasts that can move within cytoplasm –> to absorb large amounts of sunlight for photosynthesis
- Thin cell walls –> increases rate of diffusion of CO2
- Large vacuole –> to maintain turgor pressure
24
Q
See pg65 & goodnotes for palisade mesophyll cells diagram
A
+ slide micro
25
How are Root hair cells specialised for their functions
- (absorb water/mineral ions from soil, present at roots)
- Long extensions called **root hairs** --> increases SA for absorption
- **Thin, permeable** cell wall --> easy entry of water/ions
- Cytoplasm contains lots of **mitochondria** --> provide energy needed for active transport
26
See pg65 & goodnotes for root hair cells diagram
+ slide micro
27
How are Guard cells specialised for their functions
- (found in pairs on surface of leaves, form small openings called stomata. necessary for CO2 to enter plants for photosynthesis)
- When guard cells **lose water & become less swollen** as a result of osmotic forces, they change shape & the stoma closes to prevent further water loss from the plant
- In **light**, guard cells take up water & become turgid
- **Thin outer walls** & **thickened inner walls** --> force them to bend outwards, opening stomata - allows gas exchange for photosynthesis
28
see pg65 & goodnotes for guard cells diagram
+ slide micro
29
What is stem cell potency
- The stem cell's ability to differentiate into different cell types is called **potency**.
- The greater the no. of cell types it can differentiate into, the greater its potency.
30
4 levels of stem cell potency
1. Totipotent
2. Pluripotent
3. Multipotent
4. Unipotent
31
What is Totipotent
These stem cells can differentiate into any type of cell.
32
What is Pluripotent
These stem cells can form all tissue types BUT not whole organisms.
33
What is Multipotent
These stem cells can only form a range of cells within a certain type of tissue.
34
What is Unipotent
These stem cells can only form one type of tissue.
35
Key thing about stem cell potency
Once they branch out they cannot go back to previous potency.
See potency tree diagram on goodnotes?
