Cell specialization

Question 1

zygote

Answer 1

cells can specialize along any pathway (can differentiate into any type of a cell) - pregnancy starts with cell specialization

Question 2

morula

Answer 2

last stage of early embryonic development - 16-32 cells - contains totipotent SC

Question 3

when does cell specialization start

Answer 3

when morula turs into blastocyst that is when cells migrate towards the edge of the ball structure and create a cavity - morphogens released (they impact the gene expression of cells - zygote by itself can only produce clones of unspecialized cells)

Question 4

morphogens

Answer 4

chemical signals released by some cells (during the blastocyst stage) - they get released and diffuse - the cells specialize according to what concentration of morphogens they are exposed to - morphogen gradient (indicate to a cell its position in the embryo)

Question 5

stem cells

Answer 5

cells with the ability to divide endlessly and differentiate along different pathways

Question 6

specialized cell division

Answer 6

no specialized cells can divide - they just develop, die, and then get replaced by newly specialized cells - only cancerous cells can divide endlessly

Question 7

types of SC

Answer 7

embryonic which are divided into totipotent and pluripotent, and multipotent, also called tissue-specific SC

Question 8

Totipotent SC

Answer 8

can become any cell type in the body, can give rise to the placenta as well (those on the edge of the ball structure), have all genes switched on/expressed – zygote, morula

Question 9

Pluripotent SC

Answer 9

can become any type of cell in the body but not the placenta (genes for that have already been switched off in earlier phases) – once specialized, SC divide few more times and produce cells with the same function – blastocyst, inner cell mass (can give rise only to the baby)

Question 10

Multipotent SC (tissue-specific SC)

Answer 10

in the liver, skin, and bone marrow – important for the regeneration of adult tissues (liver has a great regeneration capacity – 40% transplanted, in 6 months becomes whole) – develops into cells within a narrow group (organ) – still present once the baby is born and stays there during adulthood as well – e.g. hematopoietic SC

Question 11

niches of SC

Answer 11

precise location of SC in the organism - this is where cells can either remain inactive for a long period or proliferate (divide endlessly) and rapidly differentiate - these are determined by the microenvironment of the niche

Question 12

niches in the embryo/adult

Answer 12

no niches in the embryo, there are only TT SC there - in adults, it is in bone marrow, hair follicles

Question 13

cell volume determines…

Answer 13

the rate of metabolism and therefore the amount of substances transported in/out of the cell

Question 14

cell surface area determines…

Answer 14

the effectiveness of the exchange of materials

Question 15

what happens if a cell is too large

Answer 15

its V is too big and the number of (for example) waste products produced exceeds the cell’s capacity to let them out – it dies.

Question 16

the SA/V ratio

Answer 16

it is the factor that limits the size of the cell. It is inversely proportional to the size of the cell. Animals and humans adapt according to this property (short and stocky on the poles, long and lanky on the equator)

Question 17

what does a smaller size mean for the cell

Answer 17

1|molecules have a shorter distance to diffuse within the cell
2|smaller cell requires fewer nutrients and waste to be transported out
3|has a relatively larger membrane for transporting materials in and out

Question 18

why does cell division happen?

Answer 18

As a cell grows, eventually the SA can no longer meet the requirements of the cell – the decreasing SA/V ratio will stimulate cell division – by dividing, the cell size is reduced and kept within SA/V limits.