6.5 Stem cells

Question 1

Define differentiation

Answer 1

The process of a cell becoming differentiated, involving the selective expression of genes in a cell’s genome.

Question 2

Define undifferentiated

Answer 2

Unspecialised cell originating from meiosis or mitosis

Question 3

Define stem cells

Answer 3

Undifferentiated cells wih the potential to differentiate into a variety of specialised cells

Question 4

What are the main 3 roles of stem cells in the body?

Answer 4

Stem cells can repeatedly undergo cell division:
Produce new cells for:
- Growth
- Development
- Tissue repair

Question 5

What phase of the cell cycle do specialised cells enter?

Answer 5

G0

Question 6

Why do specialised cells enter G0?

Answer 6

Once a cell becomes specialised, it can no longer divide

Question 7

Why do stem cells have to strictly controlled?

Answer 7

If stem cells don’t divide fast enough, tissues aren’t efficiently replaced which leads to ageing

Question 8

What is the issue with stem cells dividing too fast?

Answer 8

Uncontrolled division can result in the formation of masses of cells - tumours - which can lead to cancer

Question 9

Define the ‘potency’ of a stem cell.

Answer 9

A stem cell’s ability to differentiate into different types of cells

Question 10

What happens if a stem cell loses its potency?

Answer 10

The stem cell can no longer specialise

Question 11

What influences the potency of a stem cell?

Answer 11

The greater the number of cell types a stem cell can differentiate into, the greater its potency

Question 12

What are the 3 types of cells stem cells can differentiate into?

Answer 12

1. Totipotent
2. Pluripotent
3. Multipotent

Question 13

What are the characteristics of totipotent cells?

Answer 13

• Can differentiate into any cell type
• Can differentiate into extra-embryonic tissues e.g. amnion and umbilicus
• Form the whole organism

Question 14

Give examples of totipotent cells.

Answer 14

A fertilised egg/zygote and 8-16 cells from first few mitotic divisions

Question 15

What are the characteristics of pluripotent cells?

Answer 15

• Can form all tissue types, but not whole organisms

- Origin of different tissue types within an organism

Question 16

Where are pluripotent cells found?

Answer 16

Early embryos

Question 17

What is the characteristic of multipotent cells?

Answer 17

Only form a range of cells within certain types of tissue

Question 18

1. Give an example of multipotent stem cells.
2. Where are these found?
3. Why are these stem cells multipotent?

Answer 18

1. Haematopoetic stem cells
2. Bone marrow
3. They give rise to various types of blood cells

Question 19

What are erythrocytes also known as?

Answer 19

Red blood cells

Question 20

What are neutrophils also known as?

Answer 20

White blood cells

Question 21

Where are all blood cells derived from?

Answer 21

Stem cells in bone marrow

Question 22

Why do mammalian erythrocytes need to be regularly replaced?

Answer 22

They have a short lifespan of 120 days.

Question 23

Why do mammalian erythrocytes have a short lifespan?

Answer 23

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.

Question 24

How long do neutrophils live?

Answer 24

6 hours

Question 25

What are the 2 main sources of animal stem cells?

Answer 25

1. Embryonic stem cells

2. Tissue (adult) stem cells

Question 26

Define meristematic tissue

Answer 26

Tissue containing stem cells found at regions of growth in plants

Question 27

Where can meristems be found?

Answer 27

Tips of root, shoots and between phloem and xylem tissue

Question 28

What is the vascular cambium?

Answer 28

Meristematic tissue sandwiched between the phloem and xylem

Question 29

What do cells from the vascular cambium differentiate into?

Answer 29

Different cells present in xylem and phloem tissue.

In this way, vascular tissue grows as the plant grows

Question 30

What type of stem cell are meristems?

Answer 30

Pluripotent

Question 31

Why are stem cells be used to treat heart disease?

Answer 31

After a heart attack, cardiac muscle tissue in the heart is damaged, usually irreparably.

Question 32

Why are stem cells used to treat type 1 diabetes?

Answer 32

The body’s own immune system destroys insulin-producing cells

Question 33

Why are stem cells used to treat Parkinson’s disease?

Answer 33

Symptoms are caused by the death of dopamine-producing cells.
Drugs delay onset of the disease.

Question 34

Why are stem cells used to treat Alzheimer’s disease?

Answer 34

Brain cells are destroyed as a result of buildup of abnormal protein.
Drugs alleviate symptoms.

Question 35

Why are stem cells used to treat macular degeneration?

Answer 35

Macular degeneration causes blindess in elderly and diabetics.

Question 36

Why are stem cells used to treat birth defects?

Answer 36

Some birth defects have been reversed in mice

Question 37

Why are stem cells used to treat spinal injuries?

Answer 37

Some movement has been restored in hind limbs of rats with spinal injuries

Question 38

What are the 7 diseases stem cells can be used to treat?

Answer 38

Heart disease
Type 1 diabetes
Parkinson's disease
Alzheimer's disease
Macular degeneration
Birth defects
Spinal injuries

Question 39

What 3 other areas are stem cells used for?

Answer 39

Treatment of burns
Drug trials
Developmental biology

Question 40

How are stem cells used to treat burns?

Answer 40

Stem cells grown on biodegradable mesh can produce new skin for burn patients,
This is faster than grafting.