Unit 1: Protein control of cell division

Question 1

Describe the function of the cytoskeleton?

Answer 1

The cytoskeleton provides mechanical support and shape to cells

Question 2

Describe the function of microtubules?

Answer 2

Microtubules control the movement of
membrane-bound organelles and
chromosomes

Question 3

What type of cells are present in cytoskeleton?

Answer 3

Eukaryotic cells

Question 4

What are the two parts of the cell cycle?

Answer 4

Interphase
Mitotic phase

Question 5

Describe the three sub-phases within the interphase in the cell cycle?

Answer 5

G1:This is a growth period where proteins and organelles are synthesised
S:This is where the cell continues to grow and where DNA replication occurs
G2: this is another growth period

Question 6

Describe the two sub-phases within the mitotic phase in the cell cycle?

Answer 6

Mitosis: the chromosomal material is separated by the spindle microtubules

Cytokinesis: The separation of the cytoplasm into two daughter cells

Question 7

Describe the 4 stages of mitosis?

Answer 7

Prophase: The DNA condenses into chromosomes with each consisting of two sister chromatids. Spindle microtubules attach to chromosomes via their kinetochore in the centromere.
Metaphase: chromosomes are aligned across the metaphase plate
Anaphase: spindle microtubules shorten and sister chromatids are separated and chromosomes are pulled to opposite poles of the cell
Telophase: Chromosomes decondense and nuclear membranes form around each of the two daughter cells.

Question 8

Describe the function of cyclin-CDK’s?

Answer 8

They phosphorylate proteins that regulate progression in the cell cycle. In G1 this phosphorylation inhibits Rb protein allowing the cell cycle to progress.

Question 9

Describe the function of Retinoblastoma?

Answer 9

retinoblastoma protein (Rb) acts as a tumour suppressor by
inhibiting the transcription of genes that code for proteins needed for DNA replication

Question 10

At which stages are there checkpoints in the cell cycle?

Answer 10

G1, G2, M

Question 11

Describe the G1 checkpoint and what proteins regulate it?

Answer 11

If there is sufficient phosphorylation by G1 cyclin-CDK’s, the cell cycle moves onto the next stage, if there isn’t then the cell is held at the checkpoint

Question 12

Describe the G2 checkpoint?

Answer 12

At this checkpoint the success of DNA replication is assessed and any damage to DNA is assessed

Question 13

What does DNA damage trigger?

Answer 13

DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or initiate apoptosis

Question 14

Describe the metaphase checkpoint?

Answer 14

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

Question 15

What can cause a degenerative disease?

Answer 15

An uncontrolled decrease in the rate of the cell cycle

Question 16

What can cause a tumour to form?

Answer 16

An uncontrolled increase in the rate of the cell cycle

Question 17

What is a proto-oncogene?

Answer 17

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

Question 18

What types of cell death signals are there that can trigger apoptosis (programmed cell death)?

Answer 18

Apoptosis is triggered by cell death signals
that can be external or internal

Question 19

What’s an example of an external death signal?

Answer 19

The production of death signal molecules from lymphocytes is an example of an external death signal.

Question 20

Whats an example of an internal death signal?

Answer 20

DNA damage is an example of an internal death signal.

Question 21

Describe the function of external death signals?

Answer 21

External death signal molecules bind to a surface receptor protein and trigger a protein cascade within the cytoplasm

Question 22

Describe the function of internal death signals?

Answer 22

An internal death signal resulting from DNA damage causes activation of p53 tumour-suppressor protein

Question 23

What do both types of death signals result in?

Answer 23

Both types of death signal result in the activation of caspases (types of protease enzyme) that cause the destruction of the cell

Question 24

Why is apoptosis necessary?

Answer 24

Apoptosis is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis. for example cells between fingers of animals.

Question 25

What are microtubules composed of?

Answer 25

Proteins called tubulin