Stem Cells

Question 1

What is a stem cell

Answer 1

A cell that can divide (by mitosis) an unlimited amount of times

Question 2

What does each new cell produced by the division of a stem cell have the ability to do

Answer 2

It has the ability to remain a stem cell or develop into a specialised cell (by a process called differentiation)

Question 3

What is the definition of potency

Answer 3

They ability of stem cells to differentiate into specialised cells

Question 4

What are totipotent stem cells

Answer 4

Stem cells that can differentiate into any cell type found in an embryo as well as extra embryonic cells.

Question 5

What is the potency of a zygote

Answer 5

It’s totipotent as are the embryonic cells up to the 16th cell stage of human embryo development.

Question 6

What is pluripotent

Answer 6

Pluripotent stem cells are embryonic stem cells that can differentiate into any cell type found in an embryo, but aren’t able to differentiate into extra embryonic cells.

Question 7

What is multipotency

Answer 7

They are adult stem cells that have lost some of the potency associated with embryonic stem cells and are no longer pluripotent.

Question 8

What happens as tissues, organs and organ systems develop

Answer 8

The cells become more and more specialised.

Question 9

What happens to adult cells and why

Answer 9

Having differentiated and specialised to fulfil particular roles, most adult stem cells gradually lose the ability to divide until they are no longer able to.

Question 10

What are adult stem cells

Answer 10

A small number of stem cells that remain to produce new cells for essential processes of growth cell replacement and tissue repair.

Question 11

What is the potency of adult stem cells

Answer 11

They are only able to produce a limited range of cell types - therefore they are multipotent adult stem cells (they can only differentiate into blood cells)

Question 12

Where can multipotent stem cells be found in the body

Answer 12

They can be found throughout the body (bone marrow, skin, gut, brain)

Question 13

What are erythrocytes

Answer 13

Red blood cells specialised to aid oxygen transport around the body

Question 14

because red blood cells lack a nucleus how are more produced

Answer 14

Because they lack a nucleus they can’t perform mitosis to give rise to new cells; this means that erythrocytes directly form from adult stem cells in the bone marrow to maintain the red blood cell count in the blood.

Question 15

What are the changes in cell structure when the adult stem cells specialise into erythrocytes

Answer 15

-> loss of nucleus
-> shape change to form a biconcave disc
-> increase production of haemoglobin protein
-> increase in membrane flexibility

Question 16

What are neutrophils

Answer 16

A type of white blood cell that is specialised to destroy pathogens by phagocytosis

Question 17

How are neutrophils produced

Answer 17

They are produced from the same adult stem cells as the erythrocytes

Question 18

What are some changes that occur when the adult stem cells differentiate into neutrophils

Answer 18

-> indentations form in the nucleus giving it a lobed structure
-> Production of hydrolytic enzymes increases
-> Lysosomes that contain hydrolytic enzymes accumulate
-> membrane flexibility increases

Question 19

What are meristems

Answer 19

Meristems are where plant stems cells are found

Question 20

Two examples of differentiated cells that are from the meristem

Answer 20

Xylem and phloem

Question 21

Where are the specialised cells that make xylem and phloem up found

Answer 21

They are located in the meristems and the cambium cells are found between regions of xylem and phloem tissue in plant stems and roots.

Question 22

What are some changes that occur when cambium differentiates into xylem

Answer 22

Deposition of lignin in cell walls
Loss of cytoplasm
Loss of end walls

Question 23

What are some changes that occur when cambium differentiates into phloem

Answer 23

Reduction in cytoplasm volume
Loss of organelles
End walls -> sieve tubes