1. Key Area 5- Protein Control and Cell Division

Question 1

What is the purpose of the cytoskeleton?

Answer 1

To give 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 composed of?

Answer 3

They are hollow cylinders composed of the protein tubulin. They radiate from the microtubule organising centre (MTOC) or centrosome

Question 4

What is the function of microtubules?

Answer 4

Control the movement of membrane-bound organelles and chromosomes

Question 5

What does cell division require?

Answer 5

The remodelling of the cytoskeleton

Question 6

What does the formation and breakdown of microtubules involve?

Answer 6

Polymerisation and depolymerisation of tubulin

Question 7

What do microtubules form?

Answer 7

The spindle fibres that are active during cell division

Question 8

What does the cell cycle consist of?

Answer 8

Interphase and Mitotic phase

Question 9

What does interphase involve?

Answer 9

The growth and DNA synthesis including G1: growth phase, S phase: during which the DNA is replicated, and G2: a further growth phase

Question 10

What does the mitotic phase involve?

Answer 10

mitosis and cytokinesis

Question 11

What occurs in mitosis?

Answer 11

the chromosomal material is separated by the spindle microtubules

Question 12

When and what occurs in cytokinesis?

Answer 12

Following mitosis, the cytoplasm is separated into two daughter cells

Question 13

What does mitosis consist of?

Answer 13

PMAT
prophase
metaphase
anaphase
telophase

Question 14

What happens in prophase?

Answer 14

DNA condenses into chromosomes consisting of sister chromatids. Nuclear membrane breaks down, spindle microtubules extend from the MTOC (microtubule organising centre) by polymerisation and attach to chromosomes via their kinetochores in the centromere region

Question 15

What happens in metaphase?

Answer 15

Chromosomes are aligned at the metaphase plate (equator of the spindle)

Question 16

What happens in anaphase?

Answer 16

As spindle microtubules shorten by depolymerisation, sister chromatids are separated and the chromosomes are pulled to opposite poles

Question 17

What happens in telophase?

Answer 17

The chromosomes decondense and nuclear membranes are formed around them

Question 18

Define the mitotic index

Answer 18

A measure of the activity of a particular tissue. The number of cells in M/ total cells as a percentage

Question 19

What is progression through the cell cycle controlled by?

Answer 19

Checkpoints

Question 20

What are checkpoints?

Answer 20

They are mechanisms within the cell that assess the condition of the cell during the cell cycle and halt progression to the next phase until certain requirements are met

Question 21

What accumulates during cell growth which is involved in regulating the cell cycle?

Answer 21

Cyclin proteins

Question 22

What do cyclins combine with and activate?

Answer 22

cyclindependent kinases (CDKs)

Question 23

What do active cyclindependent kinases complexes (CDKs) do?

Answer 23

They phosphorylate proteins that regulate progression through the cycle. If sufficient phosphorylation is reached, progression occurs

Question 24

Where does the retinoblastoma protein (Rb) acts as a tumour suppressor?

Answer 24

At the G1 checkpoint

Question 25

How does the retinoblastoma protein (Rb) act as a tumour suppressor?

Answer 25

By inhibiting transcription of genes that code for proteins needed for DNA replication

Question 26

What inhibits the retinoblastoma (Rb) protein?

Answer 26

Phosphorylation by G1-cyclin-CDK

Question 27

What is the order of the cell cycle?

Answer 27

G1 to S phase to G2 to M phase

Question 28

What is assessed at the G2 checkpoint?

Answer 28

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

Question 29

What does DNA damage trigger at the G2 checkpoint?

Answer 29

DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death.

Question 30

What is the function of the protein p53?

Answer 30

Stimulates DNA repaire, arrests the cell cycle or causes cell death

Question 31

What controls the progression from metaphase to anaphase?

Answer 31

The metaphase checkpoint

Question 32

What happens at the metaphase checkpoint?

Answer 32

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

Question 33

What does an uncontrolled reduction in the rate of the cell cycle result in?

Answer 33

Degenerative disease

Question 34

What does an uncontrolled increase in the rate of the cell cycle result in?

Answer 34

Tumour formation

Question 35

What is the function of a proto-oncogene?

Answer 35

It is a normal gene which is usually involved in the control of cell growth or division which can mutate to form a tumour-promoting oncogene

Question 36

What is apoptosis triggered by?

Answer 36

Cell death signals which can be internal or external

Question 37

Once external death signal molecules bind to a surface receptor protein, what do they trigger?

Answer 37

A protein cascade within the cytoplasm

Question 38

What is an example of an external death signal?

Answer 38

The production of death signal molecules from lymphocytes

Question 39

What is an example of an internal death signal?

Answer 39

DNA damage

Question 40

What does an internal death signal resulting from DNA damage cause?

Answer 40

The activation of p53 tumour-suppressor protein

Question 41

What does both types of death signal result in?

Answer 41

The activation of caspases (types of protease enzyme) that cause the destruction of the cell

Question 42

Why is apoptosis essential during the development of an organism?

Answer 42

To remove cells no longer required as the development progresses or during metamorphosis

Question 43

Even in the absence of growth factors, what may cells initiate?

Answer 43

Apoptosis