1.6 PROTEIN CONTROL OF CELL DIVISION

Question 1

What is the main requirement of cell division?

Answer 1

Remodelling of the cell’s cytoskeleton

Question 2

What is the cytoskeleton?

Answer 2

Microscopic network of protein filaments and tubules in the cytoplasm

Question 3

What is the purpose of the cytoskeleton?

Answer 3

To give mechanical support and shape to cells

Question 4

What does the cytoskeleton consist of?

Answer 4

Different types of proteins extending throughout the cytoplasm

Question 5

What are microtubules composed of?

Answer 5

Hollow straight rods

Question 6

What are the rods that make up microtubules made of?

Answer 6

Globular proteins known as tubulins

Question 7

What is the purpose of microtubules?

Answer 7

To govern location and movement of membrane-bound organelles and other cell components

Question 8

Where are microtubules found?

Answer 8

All eukaryotic cells

Question 9

Where do microtubules radiate from?

Answer 9

The microtubule organising centre (MTOC)

Question 10

What is the MTOC also known as?

Answer 10

The centrosome

Question 11

Which necessary structure do microtubules form during cell division?

Answer 11

Spindle fibres

Question 12

What does the cell cycle regulate?

Answer 12

Growth and replacement of genetically identical cells

Question 13

Over what time period does the cell cycle regulate growth and replacement of cells?

Answer 13

The entire life of the organism

Question 14

Unconrolled reduction in rate of cell cycle could result in?

Answer 14

A degenerative disease

Question 15

Unconrolled increase in rate of cell cycle could result in?

Answer 15

Tumour formation

Question 16

What are the three stages of the cell cycle?

Answer 16

Interphase, mitosis, cytokinesis

Question 17

What is interphase?

Answer 17

Cell growth divided into three further stages

Question 18

What are the three sub-phases of interphase?

Answer 18

G1, S phase, G2 phase

Question 19

What occurs during G1 phase?

Answer 19

Proteins and organelles synthesised

Question 20

What occurs during S phase?

Answer 20

Cell continues to grow, DNA replication

Question 21

What occurs during G2 phase?

Answer 21

More growth - more proteins and organelles synthesised

Question 22

What follows interphase?

Answer 22

Mitotic phase

Question 23

What are the four stages of mitosis?

Answer 23

PMAT - prophase, metaphase, anaphase, telophase

Question 24

What happens to chromosomes during prophase?

Answer 24

Each duplicated chromosome appears as two identical sister chromatids joined at the centromere

Question 25

What happens in the cytoplasm during prophase?

Answer 25

Mitotic spindle begins to form

Question 26

Where does mitotic spindle begin to form during prophase?

Answer 26

Between two centrosomes

Question 27

What happens to chromosomes during metaphase?

Answer 27

They line up on metaphase plate in centre of cell

Question 28

What attaches to chromatids during metaphase?

Answer 28

Microtubules from opposite ends of parent cell

Question 29

Where do microtubules join to chromatids?

Answer 29

At the kinetochore

Question 30

What happens during anaphase?

Answer 30

Spindle fibres shorten

Question 31

What is the result of spindle fibres shortening?

Answer 31

Sister chromatids move apart as paired centromeres separate

Question 32

What happens to the cell during telophase?

Answer 32

Lengthens and nuclear membranes form around each set of chromosomes

Question 33

What happens to chromosomes during telophase?

Answer 33

Begin to uncoil

Question 34

Which stage of the cell cycle also takes place during telophase?

Answer 34

Cytokinesis

Question 35

What does cytokinesis involve?

Answer 35

Separation of cytoplasm into two daughter cells

Question 36

What regulates progression through the cell cycle?

Answer 36

Checkpoints

Question 37

What are checkpoints?

Answer 37

Critical control points which signal stop and go ahead

Question 38

Where are the three checkpoints in the cell cycle?

Answer 38

G1, G2, Metaphase

Question 39

Which is the most important checkpoint for many cells?

Answer 39

G1 checkpoint

Question 40

What is the result of a go ahead signal not being reached at G1 checkpoint?

Answer 40

Cell may switch to G0 phase

Question 41

What is G0 phase?

Answer 41

Non-dividing state

Question 42

What happens as cell size increases during G1 phase?

Answer 42

Cyclin proteins accumulate

Question 43

What do cyclin proteins combine with?

Answer 43

Cyclin-dependant kinases (Cdks)

Question 44

What are cyclin-dependant kinases?

Answer 44

Regulatory proteins

Question 45

What is the result of cyclin proteins combining with Cdks?

Answer 45

Cyclin-dependant kinases are activated

Question 46

What do activated Cdks do?

Answer 46

Cause phosphorylation of proteins that stimulate cell cycle

Question 47

What results in a go ahead signal at G1 checkpoint?

Answer 47

Threshold of phosphorylation of cell cycle-stimulating proteins by Cdks is surpassed

Question 48

What results in a stop signal at G1 checkpoint?

Answer 48

Insufficent phosphorylation of cell cycle-stimulating proteins by Cdks

Question 49

What does the G1 Cdk do?

Answer 49

Phosphorylates retinoblastoma (Rb)

Question 50

What is a retinoblastoma protein?

Answer 50

A transcription factor inhibitor

Question 51

What is the phosphorylation of Rb protein allow?

Answer 51

DNA replication in S phase

Question 52

What does DNA damage trigger?

Answer 52

Activation of several proteins including p53

Question 53

What can p53 do?

Answer 53

Stimulate DNA repair, arrest the cell cycle, cause cell death

Question 54

What must be carefully controlled in a multicellular organism?

Answer 54

Cell destruction

Question 55

What is apoptosis?

Answer 55

Programmed cell death

Question 56

What is apoptosis triggered by?

Answer 56

Cell death signals

Question 57

What do cell death signals activate?

Answer 57

Inactive forms of DNAase and proteinases (caspases)

Question 58

What do activated DNAases and proteinases (caspases) do?

Answer 58

Destroy the cell

Question 59

Where may cell death signals come from?

Answer 59

May originate outwith the cell

Question 60

Name a possible source of extracellular cell death signals.

Answer 60

Lymphocytes

Question 61

Where are receptors for extracellular cell death signals found?

Answer 61

Cell surface

Question 62

What is the result of an extracellular cell death signal binding to its receptor?

Answer 62

Activation of caspase-producing protein cascade

Question 63

Name a possible source of intracellular cell death signals.

Answer 63

p53 protein

Question 64

How does p53 protein trigger cell death?

Answer 64

Activation of caspase cascade

Question 65

Name one other reason cells may initaite apoptosis.

Answer 65

Absence of cell growth factors