KA6 -Protein Control of Cell Division

Question 1

What does the cytoskeleton give to cells?

Answer 1

Cytoskeleton gives mechanical support and shape to cells

Question 2

What does the cytoskeleton consist of?

Answer 2

Different types of proteins extending throughout the cytoplasm

Question 3

What are tubulins?

Answer 3

Microtubules composed of hollow straight rods made of globular proteins

Question 4

Tubulins govern…

Answer 4

The location and movement of membrane-bound organelles and other cell components

Question 5

Where are microtubules found?

Answer 5

In all eukaryotic cells

Question 6

What do microtubules do?

Answer 6

Radiate from the centrosome (the microtubules organising centre)

Question 7

What do microtubules form?

Answer 7

Spindle fibres, which are active during cell division

Question 8

What does the cell cycle regulate?

Answer 8

The growth and replacement of genetically identical cells throughout the life of the organism

Question 9

What may uncontrolled reduction in the rate of the cell cycle result in?

Answer 9

Degenerative disease

Question 10

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

Answer 10

Tumour formation

Question 11

What does the cell cycle consist of?

Answer 11

Interphase and mitosis

Question 12

What does the interphase consist of?

Answer 12

An initial growth phase G1 followed by an S phase where the cell continues to grow and copies its chromosomes and a further G2 growth phase, in preparation for M phase (mitosis and cytokinesis)

Question 13

What is mitosis?

Answer 13

A dynamic continuum of sequential changes described as prophase, metaphase, anaphase and telophase

Question 14

What is the role of spindle fibres?

Answer 14

?

Question 15

What is cytokinesis?

Answer 15

The separation of the cytoplasm into daughter cells

Question 16

Progression through the cell cycle is regulated by checkpoints. Where?

Answer 16

G1, G2 and metaphase

Question 17

Checkpoints are critical control points. What do they do?

Answer 17

Where stop and go ahead signals regulate the cycle

Question 18

If a go ahead signal is not reached at the G1 checkpoint, what may happen?

Answer 18

The cell may switch to a non-dividing started, called the G0 phase

Question 19

As cell size increases during G1, what happens?

Answer 19

Cyclin proteins accumulate and combine with regulatory proteins called cyclin-dependent kinases (Cdks) and activate them

Question 20

What do active Cdks cause?

Answer 20

Phosphorylation of proteins that stimulate the cell cycle

Question 21

If a sufficient threshold of phosphorylation is reached, what happens?

Answer 21

The cell cycle moves on to the next stage

Question 22

What happens when an insufficient threshold is reached?

Answer 22

The cell is held at a checkpoint

Question 23

What does the G1 Cdk phosphorylate? What does this allow for?

Answer 23

A transcription factor inhibitor - retinoblastoma (Rb) protein

This allows for DNA replication in the S phase

Question 24

What does DNA damage trigger? What does this stimulate?

Answer 24

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

Question 25

What is the most important checkpoint for many cells?

Answer 25

G1 checkpoint

Question 26

What must be carefully controlled in a multicellular organism?

Answer 26

Destruction of cells

Question 27

What is another name for programmed cell death?

Answer 27

Appoptosis

Question 28

What is programmed cell death triggered by?

Answer 28

Cell death signals that activate inactive forms of DNAase and proteins sea (caspases) that destroy the cell

Question 29

Where may cell death signals originate? Give an example. Where may they bind?

Answer 29

Out with the cell -
Lymphocytes
Bind to a surface receptor protein to activate a protein cascade that produces active caspases

Question 30

Death signals may also originate from where? Give an example of this.

Answer 30

Within the cell

As a result of DNA damage the presence of p53 protein can activate a caspase cascade

Question 31

In the absence of cell growth factors, what may happen?

Answer 31

Initiate apoptosis