Protein Control of Cell Division

Question 1

What is the purpose of the cytoskeleton?

Answer 1

It gives mechanical support and shape to cells

Question 2

What does the cytoskeleton consist of?

Answer 2

different protein structures including microtubules, which are found In all eukaryotic cells

Question 3

What are microtubules?

Answer 3

hollow cylinders composed of the protein tubulin

Question 4

Where do the microtubules radiate from?

Answer 4

The microtubule organising centre (MTOC) or centrosome

Question 5

What do microtubules do?

Answer 5

control the movement of membrane-bound organelles and chromosomes

Question 6

What do microtubules form that are active during cell division?

Answer 6

spindle fibres

Question 7

What does the formation and breakdown of microtubules involve?

Answer 7

polymerisation and depolymerisation of tubulin

Question 8

What does interphase involve?

Answer 8

growth and DNA synthesis

Question 9

What phases does interphase include?

Answer 9

G1, S phase and G2

Question 10

What is G1?

Answer 10

a growth phase

Question 11

What happens during S phase?

Answer 11

The DNA is replicated

Question 12

What is G2?

Answer 12

Further growth phase

Question 13

In mitosis, what separates the chromosomal material?

Answer 13

The spindle microtubules

Question 14

What is separation of the chromosomal material by spindle microtubules followed by?

Answer 14

cytokinesis

Question 15

What is cytokinesis?

Answer 15

The process where the cytoplasm is separated into two daughter cells

Question 16

What are checkpoints?

Answer 16

Mechanisms within the cell that assess the condition of the cell during the cell cycle

Question 17

What do checkpoints do?

Answer 17

Halt progression to the next phase until certain requirements are met

Question 18

When do cyclin proteins accumulate?

Answer 18

during cell growth

Question 19

What do cyclins do?

Answer 19

regulate the cell cycle

Question 20

What do cyclins combine with and activate?

Answer 20

cyclin-dependent kinases (CDKs)

Question 21

What do active cyclin-CDK complexes do?

Answer 21

phosphorylate proteins that regulate progression through the cycle

Question 22

At G1 checkpoint what does the retinoblastoma protein (Rb) act as?

Answer 22

A tumour suppressor; it inhibits the transcription of genes that code for proteins needed for DNA replication

Question 23

What does the phosphorylation by G1 cyclin-CDK do?

Answer 23

Inhibits the Rb

Question 24

What does the inhibition of Rb allow?

Answer 24

transcription of the genes that code for proteins needed for DNA replication

Question 25

What does inhibition of Rb enable?

Answer 25

the cells to progress from G1 to S phase

Question 26

What happens at G2 checkpoint?

Answer 26

the success of DNA replication and any damage to DNA is assessed

Question 27

What happens if any DNA damage is identified?

Answer 27

The activation of several proteins including p53 is triggered

Question 28

What does p53 do?

Answer 28

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

Question 29

What happens at the metaphase checkpoint?

Answer 29

progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules.

Question 30

What can uncontrolled increase /reduction in the rate of the cell cycle cause?

Answer 30

tumour formation i.e cancer and degenerative disease i.e alzheimers

Question 31

what do proto-oncogenes do?

Answer 31

usually involved in the control of cell growth or division

Question 32

Proto-oncogenes can mutate to form....

Answer 32

tumour-promoting oncogenes

Question 33

What can apoptosis be triggered by?

Answer 33

cell death signals that can be external or internal

Question 34

Example of external death signal?

Answer 34

The production of death signal molecules from lymphocytes

Question 35

Example of an internal death signals?

Answer 35

DNA damage

Question 36

What do external death signal molecules do?

Answer 36

Bind to a surface receptor protein and trigger a protein cascade within the cytoplasm

Question 37

What does an internal death signal do?

Answer 37

causes activation of p53

Question 38

What do both death signals activate?

Answer 38

caspases that cause the destruction of the cell

Question 39

When is apoptosis essential?

Answer 39

during development of an organism to remove cells no longer required as development progresses or during metamorphosis

Question 40

Why does apoptosis occur?

Answer 40

It removes cells no longer required as development progresses or during metamorphosis

Question 41

When may cells initiate apoptosis?

Answer 41

in the absence of growth factors

Question 42

What is apoptosis?

Answer 42

programmed cell death

Question 43

What are caspases?

Answer 43

a family of protein digesting enzymes