stem cells

Question 1

define stem cell

Answer 1

undifferentiated cell with the potential to differentiate into a variety of the specialised cell types of the organism

Question 2

define undifferentiated

Answer 2

unspecialised cell originating from mitosis or meiosis

Question 3

define totipotent

Answer 3

stem cells capable of dividing to produce all cell types to form a whole organism

Question 4

define pluripotent

Answer 4

stem cells capable of dividing to produce all cell types but not extraembryonic membranes so not a whole organism

Question 5

define multipotent

Answer 5

stem cells capable of dividing to produce several cell types

Question 6

what is a embryonic stem cell

Answer 6

another name for a pluripotent stem cell

Question 7

what is an adult stem cell

Answer 7

another name for a multipotent stem cell

Question 8

describe the characteristic abilities of stem cells compared to specialised cells.

Answer 8

• stem cells are able to undergo cell division indefinitely, specialised cells are not able to undergo cell division at all
• stem cells can differentiate into other cell types, specialised cells can’t

Question 9

explain the importance of stem cells

Answer 9

source of new cells for growth, development and tissue repair

Question 10

why must stem cell activity be carefully controlled?

Answer 10

• not dividing fast enough = tissues not efficiently replaced = ageing
• dividing too quickly without control = tumors which could lead to cancer

Question 11

state the 3 types of stem cell and give examples of where they occur in animals

Answer 11

• totipotent - zygote + the 8/16 cells from its first few mitotic divisions
• pluripotent (embryonic stem cells) - early embryos
• multipotent (adult stem cells) - bone marrow

Question 12

state where stem cells occur in plants and state which potency they have

Answer 12

• found in meristematic tissue (meristems) - wherever growth is occurring in plants
• also found between xylem and phloem - vascular cambium
• pluripotent

Question 13

outline how a cell becomes specialised

Answer 13

• stem cells in the cell cycle replicate indefinitely until
• specific genes within stem cell activate so it differentiates by expressing features required for its function + becomes specialised
• cell has entered G0 once specialised and cannot divide anymore

Question 14

explain why it is important for erythrocytes to be constantly produced.

Answer 14

• essential for transport of oxygen around the body
• short lifespan (120 days) so they need to be replaced constantly

Question 15

explain why it is important for neutrophils to be constantly produced

Answer 15

• important role in immune system
• only live about 6 hours so must constantly be replaced (even more produced when infected)

Question 16

outline how xylem vessels and phloem sieve tubes are produced from meristems

Answer 16

• meristematic tissue located between xylem and phloem tissues - vascular cambium
• cells originating from this region differentiate into diff cells present in xylem and phloem tissues

Question 17

state 7 diseases that stem cells have the potential to treat

Answer 17

• heart disease
• type 1 diabetes
• parkinson’s disease
• alzheimer’s disease
• macular degeneration
• birth defects
• spinal injuries

Question 18

suggest how stem cells could be used to treat heart disease

Answer 18

stem cells repair damage in muscle tissue in heart caused by heart attack

Question 19

suggest how stem cells could be used to treat type 1 diabetes

Answer 19

• replace insulin producing cells in pancreas that were destroyed by body’s own immune system

Question 20

suggest how stem cells could be used to treat parkinson’s disease

Answer 20

replace dead dopamine-producing cells in brain

Question 21

suggest how stem cells could be used to treat Alzheimer’s disease

Answer 21

replace brain cells destroyed due to buildup of abnormal proteins

Question 22

suggest how stem cells could be used to treat macular degeneration

Answer 22

replacing cells in retina to prevent blindness in elderly and diabetics

Question 23

suggest how stem cells could be used to treat spinal injuries

Answer 23

replacing damaged spinal cords using stem cell implants

Question 24

suggest how stem cells could be used to treat burns

Answer 24

• stem cells grown on biodegradable meshes can produce new skin for burn patients
• quicker than taking graft from another part of body

Question 25

state two ways in which stem cells may be useful in research.

Answer 25

• drug trials
• developmental biology

Question 26

describe how stem cells may be useful in drug trials

Answer 26

new drugs can be tested on cultures of stem cells before being tested on animals and humans

Question 27

describe how stem cells may be useful in developmental biology

Answer 27

because they can divide indefinitely + differentiate into various types of cells they can be used to study changes that occur as multicellular organisms grow + develop from a single cell + why things go wrong

Question 28

Describe arguments for the use of embryonic stem cells for research and medicine.

Answer 28

• allow us to find treatments for incurable diseases
• allow us to study developmental biology more closely
• embryos used were donated from those left over after fertility treatment - would have been discarded anyway

Question 29

describe arguments against the use of embryonic stem cells for research and medicine.

Answer 29

• “life begins at conceptions and destruction of embryos is murder”
• experiments do not guarantee any benefits to human life

Question 30

Define induced pluripotent stem cell

Answer 30

adult stem cells that have been genetically modified to act like embryonic stem cells/pluripotent stem cells

Question 31

explain why induced pluripotent stem cells may be useful in research and medicine

Answer 31

• could be useful replacement for actually harvesting embryonic stem cells - not as controversial
• can readily be made in a lab