maintaining body structures (W10)

Question 1

what is pausing in the cell cycle regulated by

Answer 1

CDKs (cell dependant kinases) - relieve breaks in cycle

Question 2

what external signals control CDKs

Answer 2

mitogens

Question 3

examples of mitogens

Answer 3

PDGF - platelet-derived growth factor
EGF - epidermal growth factor
erythropoietin

Question 4

what are growth factors

Answer 4

extracellular signal proteins which stimulate cell growth (increase in cell mass)

Question 5

how do growth factors work

Answer 5

promote synthesis of proteins and other macromolecules and inhibit their degredation

Question 6

example of factor that inhibits growth? specific function?

Answer 6

myostatin (specifically inhibits growth of myoblasts - muscle precursors)

Question 7

what factors regulate cell death

Answer 7

survival/death factors

Question 8

motor neuron production in embryonic stage?

Answer 8

increase in first half (survival factor independent), decrease in second half (survival factor dependant)

Question 9

cancer cells relation with growth control mechanisms and survival signals? Why could this be significant?

Answer 9

lost normal growth control mechanisms but may retain dependency on survival signals. Therefore suppressing survival signals could potentially be used to combat cancer

Question 10

mechanisms of organ/tissue growth? (mouse experiment)

Answer 10

remove spleen from mouse and add different numbers of foetal spleens will result in the same overall size of spleen (extrinsic mechanism)
if you do the same with thymus glands they grow to normal size (intrinsic mechanism)

Question 11

is there a universal mechanism for organ growth?

Answer 11

NO!!!!

Question 12

where are stem cells located in the small intestine?

Answer 12

crypts

Question 13

name for rapidly dividing cells in crypt of small intestine

Answer 13

transit amplifying cells

Question 14

2 mechanisms of stem cell renewal?

Answer 14

asymmetric division
independent choice (determined by environmental factors)

Question 15

what are intestinal stem cells influenced by

Answer 15

signals from Paneth cells and connective tissue surrounding crypt

Question 16

what is WNT?

Answer 16

secreted signalling molecule

Question 17

what is Apc?

Answer 17

inhibitory component of WNT pathway

Question 18

what effect does the absence of WNT have on Apc

Answer 18

in the absence of WNT, Apc degrades beta-catenin

Question 19

what effect does the presence of WNT have on Apc

Answer 19

In the presence of WNT, Apc is inhibited

Question 20

what is beta-catenin? what is its function

Answer 20

transcriptional factor.
drives proliferation and stem cell state

Question 21

where is WNT produced and secreted

Answer 21

Paneth cells

Question 22

which cells have WNT receptors

Answer 22

intestinal stem cells

Question 23

WNT pathway summarised?

Answer 23

Paneth cells produce & secrete WNT
WNT receptors on stem cells recieve WNT & inhibit Apc
Apc can’t degrade beta-catenin
beta-catenin translocated to nucleus & causes proliferation & stem cell state

Question 24

causes of cell death

Answer 24

mutation (external causes eg radiation, or spontaneous DNA damage, replication errors)
DNA repair declines with age
mitochondrial damage (less ATP)
damage macromolecules (proteins, DNA)
Shrinking telomeres (protective cap on chromosomes, if not working causes DNA damage)
infection/trauma