1.5: protien control of cell division

Question 1

what is the cytoskeleton

Answer 1

a fibrous framework that gives mechanical support and structure to a cell

Question 2

what are cytoskeletons made from

Answer 2

consist of different protein structures including microtubules found in all eukaryotic cells

Question 3

what are microtubules

Answer 3

hollow rods composed of the protien tubulin

Question 4

what do microtubules do

Answer 4

control the movement of membrane bound organelles that are attached to them and the movement of chromosomes during cell division

Question 5

what causes the change in size of microtubules

Answer 5

polymerisation and depolymerisation

Question 6

what does cell division require

Answer 6

remodelling of the cytoskeleton

Question 7

what do microtubules form

Answer 7

form the spindle fibres active during cell division

Question 8

what are the two phases of the cell cycle

Answer 8

interphase and miotic phase

Question 8

what does the miotic phase involve

Answer 8

mitosis and cytokenesis

Question 9

what are the three phases of interphase

Answer 9

G1 ( growth phase), S( DNA replication occurs), G2(further growth phases in prep for mitosis)

Question 10

what is mitosis

Answer 10

chromosomal material is separated by spindle microtubules

Question 11

what is cytokenesis

Answer 11

cytoplasm is separated into two daughter cells

Question 12

what does mitosis consist of

Answer 12

mitosis consists of prophase, metaphase, anaphase and telophase

Question 13

what occurs during prophase

Answer 13

DNA condenses into chromosomes containing two sister chromatids. The nuclear membrane breaks down and spindle fibres extend from the MTOC by polymerisation and attach to the chromosomes via centromere regions

Question 14

what occurs during metaphase

Answer 14

the chromosomes align at the metaphase plate

Question 14

what occurs during anaphase

Answer 14

spindle microtubules shorten and pull sister chromatids apart to opposite poles

Question 14

what occurs during telophase

Answer 14

chromosomes decondense and new nuclear membranes are formed around them

Question 15

how is progression of cell cycle controlled

Answer 15

controlled by checkpoints

Question 16

what are cell checkpoints

Answer 16

mechanisms within the cell that assess its condition during the cell cycle and halt progression to the next phase unless requirements are met.

Question 17

what are cyclin protiens

Answer 17

proteins that accumulate during cell growth and are involved in regulating the cell cycle

Question 18

what do cyclins combine with

Answer 18

cyclin-dependant kinases

Question 19

wat do active cyclin-CDKs do

Answer 19

phosphorylate proteins that regulate the progression throughout the cycle.

Question 20

what occurs at the G1 checkpoint

Answer 20

sell size and mass if checked. retinoblastoma acts as a tumour suppressor by inhibiting transcription of genes needed for DNA replication, however the cyclin-CDK inhibits the Rb and allows transcription to occur. cells then progress to stage S

Question 21

what inhibits retinoblastoma

Answer 21

cyclin-dependant kinase

Question 22

what does the inhibition of Rb allow

Answer 22

transcription of proteins needed for DNA replication

Question 23

what occurs at the G2 checkpoint

Answer 23

assess success of DNA replication and any damage to DNA, cells will progress to M and undergo mitosis

Question 24

what is the role of p53

Answer 24

stimulate DNA repair, arrest the cell cycle or cause cell death

Question 24

what does DNA damage trigger

Answer 24

p53

Question 25

what occurs at the metaphase checkpoint

Answer 25

controls progression from metaphase to ananphase

Question 26

why is progression halted at the metaphase checkpoint

Answer 26

to ensure chromosomes are aligned correctly on metaphase plate and are securely attached to spindle microtubules

Question 27

why should cell cycle be controlled

Answer 27

it has to be controlled to ensure daughter cells are produced at correct rate and place

Question 28

what does an uncontrolled decrease cause

Answer 28

a degenerative disease such as Alzheimer’s

Question 29

what does an uncontrolled increase cause

Answer 29

a build of cells causing tumour formation

Question 30

what are oncogenes

Answer 30

normal gene, usually involved in control of cell growth or division that can mutate to form a tumour forming protein

Question 31

what is apoptosis

Answer 31

is the controlled death of cells, programmed cell death that can occur during normal growth or development that results in the removal of old or damaged cells

Question 32

what is an extrinsic signal

Answer 32

a death signal that occurs from outside the cell

Question 33

what is an intrinsic signal

Answer 33

a death signal that occurs within the cell

Question 34

what do extrinsic signals do

Answer 34

extrinsic signal molecules bind to a surface receptor protein and triggers a protein cascade within the cytoplasm

Question 34

what is an example of an extrinsic death signal

Answer 34

death signal molecules from lymphocytes

Question 35

what do intrinsic signals do

Answer 35

can be caused by DNA damage which causes a disruption of the integrity of the mitochondria which triggers a cascade

Question 36

what do both death signals result in

Answer 36

result in activation of protease enzymes called caspases which act in cascades to cause destruction of the cell

Question 37

when is apoptosis essential

Answer 37

to remove cells no longer required

Question 38

why do cells initiate apoptosis

Answer 38

may be because of an absence of growth factors

Question 39

what is the MTOC

Answer 39

it is the microtubule organising centre and microtubules radiate from here

Question 40

what happens if go-ahead signal is not reached at checkpoint G1

Answer 40

may switch to a non dividing or resting state called G0

Question 41

what is also assessed at checkpoint G1

Answer 41

DNA damage, can trigger the activation of several proteins including p53