Key Area 6: Protein Control of Cell Division

Question 1

What structure is responsible for maintaining the shape, structure and position of all cell organelles?

Answer 1

Cytoskeleton

Question 2

What is the cytoskeleton?

Answer 2

A network of different proteins that extend through the cytoplasm

Question 3

What is the cytoplasm made up of?

Answer 3

Microtubules

Question 4

What are microtubules made up of?

Answer 4

Globular proteins tubulin

Question 5

Where are microtubules found?

Answer 5

Eukaryotic cells radiating from the centrosome

Question 6

What is the centrosome?

Answer 6

Microtubules organising centre

Question 7

What are microtubules important for?

Answer 7

Organelle location and movement of cell components

Question 8

What do microtubules do during cell division?

Answer 8

Form spindle fibres

Question 9

What is the purpose of the cell cycle?

Answer 9

Regulates growth and replacement of genetically identical cells throughout the life of an organism

Question 10

What happens if there’s an uncontrolled decrease in rate of cell cycle?

Answer 10

Degenerative diseases

Question 11

What happens if there’s an uncontrolled increase?

Answer 11

Tumour formation

Question 12

What are the four stages in cell division?

Answer 12

G1
S
G2
M

Question 13

What happens during interphase?

Answer 13

Protein synthesis, cytoplasmic organelles are synthesised and cell growth and chromosome replication

Question 14

What are the three stages in interphase?

Answer 14

G1-proteins and organelles synthesised
S- continues growth and DNA replication
G2- proteins and organelles synthesised

Question 15

What happens during mitotic phase?

Answer 15

Cell and contents divide

Question 16

What are the four stages in the mitotic phase?

Answer 16

Prophase
Metaphase
Anaphase
Telophase

Question 17

What happens during prophase?

Answer 17

Chromatin condenses into pairs of sister chromatids and mitotic spindle forms between chromosomes which have the role of separating chromatids

Question 18

What happens during metaphase?

Answer 18

Chromosomes line up at the metaphase plate (located at the centre equator of the cell) and nuclear membrane breaks up so centrosome are now at opposite poles. Microtubules attach to kinetochore

Question 19

What happens during anaphase?

Answer 19

Paired centrosomes seperate and pairs of chromatids move apart so each pole has a complete and identical set of chromosomes

Question 20

What happens during telophase?

Answer 20

Cell lengthens and nuclear membranes form around chromosomes. Chromosomes begin to uncoil

Question 21

What is cytokinesis?

Answer 21

The separation of the cytoplasm to form two identical daughter cells

Question 22

What are the three checkpoints that occur during cell cycle where stop and go signals regulate the cycle?

Answer 22

G1
G2
Metaphase

Question 23

What happens at G1 checkpoint?

Answer 23

It occurs at the end of G1 and tests specific growth must have occurred to enter the S phase

Question 24

What happens at G2 checkpoint?

Answer 24

It occurs st the end of G2 and tests DNA replication must be complete for cell cycle to continue

Question 25

What happens at metaphase checkpoint?

Answer 25

It occurs during metaphase and controls entry to anaphase and ensures chromosomes are aligned correctly on metaphase plate

Question 26

What is the most significant checkpoint?

Answer 26

G1

Question 27

What happens if the cell doesn’t pass G1 checkpoint?

Answer 27

It enters G0 which is the non-proliferating state and it’s held there until sufficient growth is achieved

Question 28

What happens during G1 phase?

Answer 28

Cyclin proteins accumulate

Question 29

What happens with cyclins?

Answer 29

Cyclins combine with regulatory proteins cyclin-dependent-kinases (cdk’s) which activate them and active cdks cause the phosphorylation of proteins that stimulate the cell cycle

Question 30

What happens if insufficient threshold of phosphorylation is reached?

Answer 30

The cell is held at that checkpoint

Question 31

What does cdks do?

Answer 31

They phosphorylase a transcription factor inhibitor called retinoblastoma

Question 32

What does retinoblastoma do?

Answer 32

Is frees the transcription factor and initiates S phase

Question 33

What is triggered when DNA is damaged?

Answer 33

p53 is activated

Question 34

What happens if DNA is damaged during S phase?

Answer 34

- stimulate DNA repair - arrest the cell cycle - cause cell death

Question 35

What is apoptosis?

Answer 35

Programmed cell death

Question 36

What two enzymes are involved in apoptosis?

Answer 36

Caspases and DNAases

Question 37

What are caspases?

Answer 37

Proteases that breakdown proteins

Question 38

What are DNAases?

Answer 38

They breakdown DNA and are activated by caspases

Question 39

How can apoptosis be triggered from outside the cell?

Answer 39

Signals binding to surface receptors to activate protein cascades that trigger active caspases

Question 40

What two ways can apoptosis be triggered from within the cell?

Answer 40

p53 activates caspase cascade | Growth factors are not present