THE CELL CYCLE 1

Question 1

what is critical to a cell in sustaining cellular life

Answer 1

the ability to divide

Question 2

how are multicellular organisms typically derived?

Answer 2

from a single cell zygote

Question 3

where exactly does cell division occur on a vast scale?

Answer 3

during embryogenesis

Question 4

why do cells divide?

Answer 4

to replace old, defective, infected or injured cells

Question 5

how are these cells removed

Answer 5

usually by apoptosis

Question 6

what exists within the cell that regulate the number of divisions a cell can undergo?

Answer 6

molecules that are highly conserved from yeast to mammals

Question 7

what factors regulate cell division

Answer 7

extrinsic and intrinsic factors

Question 8

define extrinsic factors

Answer 8

extrinsic factors are factors (availability of growth factors, space) external to the cell that dictate if a cell enters cell division or not

Question 9

what are intrinsic factors?

Answer 9

internal factors (p53, pRb, cyclin dependent kinase inhibitors) internal to the cell that dictate if a cell enters cell division or not

Question 10

can cells divide spontaneously

Answer 10

no they must be triggered to do so

Question 11

what is another term for the default state of all cells that are not dividing

Answer 11

quiescence

Question 12

only when do cells undergo cell division in mature adults

Answer 12

when tissue is damaged due to infection or injury

Question 13

what does a cell need to do before cell division?

Answer 13

it needs to synthesize all of its organelles, macromolecules and proteins

Question 14

what helps to precisely coordinate cell division

Answer 14

a group of molecules called cyclin dependent kinases

Question 15

what type of tissues exhibit the greatest rate of cell division?

Answer 15

tissues with the greatest rate of cell death via exposure to environment, food, infection eg stomach blood neutrophils, lungs etc

Question 16

give an example of cells with little to no cell division activity

Answer 16

central nervous system cells, skeleton, brain cells etc

Question 17

define cell division

Answer 17

a process in which a parent cell replicates most or all of its contents and forms two new daughter cells from this

Question 18

what are a few concerns for a cell about to divide

Answer 18

is environment favoured, is there any DNA damage, has DNA been fully replicated, has DNA been replicated only once, are chromosomes aligned correctly on the spindle

Question 19

what is the cell cycle checkpoint

Answer 19

points along the cell division cycle where the cell stops to check everything is in order

Question 20

can all cells divide in an adult organism, if not what do we call these cells

Answer 20

no, they are called post-mitotic cells examples including neurons and myocytes

Question 21

how many distinct phases of the cell cycle is there? name them

Answer 21

2. M-phase and interphase

Question 22

what is the M phase

Answer 22

the period where most of the action seems to take place

Question 23

what is interphase

Answer 23

the period between one M phase and another where nothing significant appears to be happening.

Question 24

where do cells spend the majority of their time

Answer 24

in interphase

Question 25

how long can interphase last for

Answer 25

between several days to years

Question 26

what can interphase be divided into

Answer 26

G1(gap 1), S(synthesis), and G2(gap 2)

Question 27

what prevents cells from entering s phase in the cell cycle from G1

Answer 27

the restriction point, also called start

Question 28

what prevents cells from entering s phase in the cell cycle from G1

Answer 28

the restriction point, also called start

Question 29

what drives a cell past start

Answer 29

signals from the environment

Question 30

what is G0(gap zero)

Answer 30

cells deprived of extracellular signals that are arrested in interphase at a point where they no longer divide

Question 31

what is serum

Answer 31

the fluid that remains when blood is allowed to clot

Question 32

what is in serum that allows scientists to stimulate cell division

Answer 32

growth factors

Question 33

are growth factors found in high or low concentrations

Answer 33

low

Question 34

what is PDGF

Answer 34

platelet derived growth factor, one of the first growth factors to be purified

Question 35

do growth factors show broad or narrow specificity

Answer 35

they show both

Question 36

can growth factors only bind to one GF receptor

Answer 36

no, some can bind to multiple showing some degree of promiscuity

Question 37

what do cells compete for

Answer 37

growth factors

Question 38

how do cells control the number of cell divisions

Answer 38

via extrinsic control (limiting growth factors) and intrinsic control(brakes on cycle via possession of molecules)

Question 39

what happens when cells fail to get enough growth factors

Answer 39

they fail to divide and may die

Question 40

how are tissues initially constructed in cells? what happens after this initial construction is complete?

Answer 40

initially constructed by overproduction of cells before limiting the amount of growth factor available allowing the cells to compete for it.

Question 41

what happens when a growth factor supply is switched off? give an example of where this occurs?

Answer 41

the cells in that area die from no growth factor. happens in formation of the hand from the limb bud.

Question 42

what was noted about the nervous and immune system cells? what do these cells require to happen generally for survival?

Answer 42

cells are massively overproduced in these systems. they need to have cell to cell interactions to survive.

Question 43

what does cell to cell interactions in nervous and immune systems upregulate? what does this allow the cell to do?

Answer 43

Causes the expression of growth factor receptor to be upregulated. allows the cell to absorb growth factors and survive.

Question 44

what is often considered a condition for cell division (hint: what substratum is required)?

Answer 44

it needs to attach to the extracellular matrix, which surrounds all cells within tissues.

Question 45

what are integrins and what do cells use them for ?

Answer 45

these are membrane anchored proteins that cells use to attach themselves to the extracellular matrix.

Question 46

do integrins act as sensors too?

Answer 46

yes, they relay information into the cell about matrix composition and degree that the cell is attached to the matrix.

Question 47

what do integrins do when ligand binding happens?

Answer 47

they form clusters which form focal adhesions. which impacts the organisation of the cell cytoskeleton,

Question 48

what can integrin signals also trigger?

Answer 48

cell migration, differentiation, inhibit cell death, and proliferation

Question 49

what is contact inhibition?

Answer 49

cells that become surrounded on all sides by neighbouring cells that stop dividing