6.5 Stem Cells

Question 1

What is differentiation?

Answer 1

process by which cell becomes specialised

gains specific organelles

which help it carry out a specific function.

Question 2

What is a stem cell?

Answer 2

undifferentiated cells

with the potential to divide & produce more stem cells

or differentiate to become a specialised cell with a specific function

Question 3

Why must stem cell division be strictly controlled?

Answer 3

• rate of division is not fast enough -
  
  • tissues are not replaced fast enough, leads to ageing
• rate of division is too fast -
  
  • formation of cancerous tumours

Question 4

What is stem cell potency?

Answer 4

a stem cell’s ability to differentiate into a variety of cell types

Question 5

What are the different types of stem cell potencies?

Answer 5

• TOTIPOTENT
  
  • can form any type of cell
  • can produce a whole organism
• PLURIPOTENT
  
  • can form any type of tissue
  • cannot produce a whole organism
• MULTIPOTENT
  
  • can only form range of cells within a certain type of tissue

Question 6

Where are all blood cells derived from?

Answer 6

bone marrow

Question 7

What is the average lifespan of an erythrocyte?

Answer 7

120 days

Question 8

Why is the lifespan of an erythrocyte so low?

Answer 8

lack of nucleus & organelles - cannot sustain itself for long

Question 9

What are the sources of animal stem cells & what are their potencies?

Answer 9

• EMBRYONIC STEM CELLS
  
  • present at early stage of embryonic development, where they are totipotent
  • after blastocyst forms, become pluripotent
• BONE MARROW/ADULT STEM CELLS
  
  • multipotent, but could be triggered to become pluripotent
  • present in bone marrow + umbilical cord

Question 10

What is the source of plant stem cells?

Answer 10

meristem tissue,

found at the tips of roots + shoots

Question 11

Where is meristem tissue found?

Answer 11

tips of roots + tips of shoots

(zone of division)

Question 12

What are the potential uses of stem cells?

Answer 12

treating…

• Heart disease - replace damaged tissue
• Type 1 diabetes - culture beta cells
• Parkinson’s disease - culture dopamine-producing cells in brain
• Alzheimer’s disease - culture brain cells
• Macular degeneration
• Birth defects
• Spinal injuries - fix damaged spinal cords
• BURN TREATMENT - can produce new skin, instead of taking grafts
• DRUG TRIALS - new drugs can be tested on cultures of stem cells before being tested on humans & animals

Question 13

What are the possible ethical issues concerning the use of stem cells?

Answer 13

• removal of stem cells from embryos causes its destruction
• religious objections
• some people believe life begins at conception

Question 14

Explain why the use of stem cells is considered regenerative medicine:

Answer 14

stem cells divide & differentiate

to replace damaged tissue