6.5 - Stem Cells

Question 1

What is a stem cell?

Answer 1

Undifferentiated cells that can divide indefinitely and differentiate into a range of specialised cells

Question 2

Name 4 types of stem cells

Answer 2

1. Totipotent
2. Pluripotent
3. Multipotent
4. Unipotent

Question 3

Define a totipotent cell

Answer 3

•Are able to differentiate into any type of cell found in the body
• Aldi into extra embryonic cells such as those in the placenta
• these cells are found in the embryo at an early stage called the blastocyst

Question 4

Define multipotent

Answer 4

Can differentiate into a number of closely related cell types within a certain type of tissue
Eg. Haematopoeitic adult stem cells in the bone marrow give rise to different types of blood cells

Question 5

Define unipotent

Answer 5

Cannot differentiate, but are capable of self renewal

Question 6

What are embryonic stem cells?

Answer 6

Stem cells found in embryos and can develop into almost every cell type under the right conditions in a lab

• present a very early stage of embryo development
• embryonic stem cells are totipotent before 7 days and pluripotent after the blastocyst forms

Question 7

What are some advantages of embryonic stem cells?

Answer 7

• can treat a wide variety of diseases
• can become any cell tyoe

Question 8

What are some disadvantages of embryonic stem cells?

Answer 8

• possible harm/death of the embryo
• human rights / ethical issues the embryo cannot give consent
• unreliable as this is not a well tested method

Question 9

What are some advantages of adult stem cells?

Answer 9

• no ethical issues as adult can give consent for the stem cells to be collected
• safer as this is a well tested method

Question 10

What are some disadvantages of adult stem cells?

Answer 10

• possibility of infection during extraction of stem cells
• adult stem cells can only become one type of cell ( same as the tissue it came from )
• can be very painful

Question 11

What are adult tissue stem cells?

Answer 11

• found in adult tissues eg. Bone marrow, brain , muscle
• can only differentiate into the same type of cell as the tissue they came from
• present throughout life from birth
• could be artificially triggered to become pluripotent
• can be harvested from umbilical cords of newborn babies
• in animals adult stem cells are used to replace damaged cells

Question 12

Where are plant stem cells found?

Answer 12

Meristems

Question 13

Where is the cambium in meristems in plants ?

Answer 13

Between xylem and phloem - a layer of meristem cells - they divide to produce new xylem and phloem

Question 14

What is the role of xylem in meristems in plants?

Answer 14

• transports water and minerals within plant
• meristem cells produce small cells which elongate
• walls are reinforced with waterproof lignin
• ends of cells break down
• this forms a long continuous tubes with a wide lumen
• provides support for the plant

Question 15

What is the role of phloem in meristem in plants?

Answer 15

• transports products of photosynthesis within a plant
• structure consists of sieve tubes and companion cells
• meristem tissue produces cells that elongate and line up to form end to end tubes
• ends do not break down completely
• form sieve played in between cells
• sieve plates allow for the movement of material up or down tube
• next to each sieve cell is a companion cell providing support

Question 16

What are some therapeutic examples of diseases that stem cells help with the treatment of?

Answer 16

• leukaemia- bone marrow transplants for cancer patients who are immune compromised as a result of chemotherapy
• Paraplegia - repair damage caused by spinal injuries to enable paralysed victims to regain movement
• diabetes - replace non functioning islet cells with those capable of producing insulin in type I diabetes
• burn victims - graft new skin cells to replace damaged tissue

Question 17

What are erythrocytes?

Answer 17

• red blood cells
• cell loose nucleus , mitochondria, Golgi apparatus and rough ER
• packed full of haemoglobin
• shape changes forming biconcave discs
• allows them to transport oxygen

Question 18

What are neutrophils?

Answer 18

• type of white blood cell
• keep nucleus
• cytoplasm appears granular
• large number of lysosomes produced
• aide their role of ingesting invading microorganisms

Question 19

What are some examples of stem cell therapy?

Answer 19

1. Stargatds disease
2. Parkinson’s disease
   3.

Question 20

Where do we find embryonic stem cells?

Answer 20

in the blastocyst

• the cells are inside in the inner cell mass
• embryonic stem cells taken from the inner cell mass
• they are put in fluid with nutrients and culture in the lab to grow more cells

Question 21

Define pluripotent

Answer 21

Can form any cell type ( eg. Embryonic stem cells ) but not the whole organism

Question 22

What are some examples where stem cells have been used in therapeutic regards?

Answer 22

• Leukaemia - bone marrow transplants for cancer patients who are immunocompromised as a result for chemotherapy
• paraplegia - repair damage caused by spinal injuries to enable paralysed victims to regain movement
• Diabetes - replace non- functioning islet cells with those capable of producing insulin in type 1 diabetes
• burn victims - graft new skin cells to replace damaged tissue