Protein Control of cell division

Question 1

Cytoskeleton

Answer 1

• Dynamic Intricate network of thread like filaments that fills cytoplasm
• Consists of different protein structures including microtubules

Question 2

What gives mechanical support and shape to cells

Answer 2

Cytoskeleton

Question 3

Microtubules

Answer 3

Hollow cylinders composed of the protein tubulin
Radiate from MTOC/centrosome

Question 4

Cytoskeleton is responsible for and microtubules control

Answer 4

Movement of organelles and chromosomes within it

Microtubules control cytokinesis

Question 5

Formation and breakdown of microtubules

Answer 5

Polymeristaion and depolymeristaion

Question 6

Why does mitosis require remodelling of the cytoskeleton

Answer 6

Because in mitosis microtubules form the spindle fibres which are active during mitosis, to move chromosomes and separate chromatids.

Microtubules must be dissembled and reassembled

Question 7

Microtubules provide a

Answer 7

Framework for attatching
- organelles
- ribosome subunits
- vesicles
- and even molecules,

Question 8

Dynamic nature of Cytoskeleton

Answer 8

• Continually changing to provide support and movement within a cell
• ## Microtubules can break and reform(controlled by centrosome)

Question 9

Centrosome

Answer 9

Structure involved in cell division.
- duplicates in cell division, the two centrosomes move to opposite ends of the cell.
- Micro tubules come from here
- contains centriols

Question 10

Centriole

Answer 10

Helps to arrange the microtubules that move chromosomes during cell division.

Soeach daughter cell recieves right number of chromosomes

Question 11

Cell cycle

Answer 11

Consists of
Interphase and Mitosis

Cell grows until it reaches its critical mass, then divides to produce 2

daughter cells

Question 12

Interphase

Answer 12

Involves growth and DNA synthesis and can be divided into 3 sub phases=
G1
S
G2.

Lasts 80% of the cell cycle

Question 13

G1

Answer 13

First period of cell growth stage. Cell wont divide until it has doubled in size.

Many extra cell components are also synthesised

Question 14

S (synthesis)

Answer 14

DNA replication occurs - chromosomes replicate to form two chromatids held together at centromere,

Centrioles duplicate

Question 15

MTOC in mitosis

what it normally does

Answer 15

Normally controls the cytoskeleton
but during mitosis **cytoskelton breaks down **and Microtubules are reassembled to form spindle

(centrosome)

Question 16

G2

Answer 16

A further growth phase to prepare for mitosis.

Sufficient reserves of ATP built up to last cell through rest of cycle.

Question 17

3 active processes taking place during Interphase

Answer 17

• Cell growth
• Replication of DNA
• Protein Synthesis of organelles

Question 18

Mitosis

consists of

Answer 18

Consists of Prophase Metaphase Anaphase Telophase.

Question 19

Prophase

Answer 19

• Dna Condenses into chromosomes consisting of two sister chromatids.
• Nuclear membrane breaks down
• Spindle microtubules extend from MTOC by polymerisation

Question 20

Metaphase

Answer 20

Chromosomes align at the metaphase plate

Question 21

Anaphase

Answer 21

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

Question 22

Telophase

Answer 22

Chromosomes decondense and nuclear membrane forms around them.

Question 23

What is mitosis controlled by?

Answer 23

Controlled and regulated by proteins, and checkpoints

Question 24

what are

Checkpoints

Answer 24

**Mechanisms **within cell cycle that asses condition of cell during cycle
Will halt progression to next phase until requirements are met

Question 25

When are checkpoints during cell cycle

Answer 25

- near the end of G1 - at the G2/M transition - and during metaphase

Question 26

Cyclin Proteins

Answer 26

**Accumulate **during cell growth. Involved in regulating cell cycle. They combine with Cdk's and activate them

Question 27

Cdk

Answer 27

Cyclin dependent kinases | Respitory enzymes

Question 28

Active Cdk/cyclin complexes | When sufficient phosphortylation reached

Answer 28

Phosphorylate proteins that regulate cell cycle progression | (so cell cycle can continue) ## Footnote If sufficient phosphorylation reached, progression occurs

Question 29

# G1 Checkpoint Cyclin/cdk process

Answer 29

1. Increasing cell size accumulates G1 cyclin proteins 2. Cdks combine 3. active cyclin/cdk complex formed 4. phosphorylation of proteins by complex 5. Phosphorylation threshold reached 6. Pass checkpoint to next stage

Question 30

# G1 Checkpoint Retinablastoma protein | is a ## Footnote At G1 checkpoint

Answer 30

Transcription inhibitor factor. Inhibits transcription of genes that code for proteins needed for DNA replication at G1 checkpoint | (prevents progression of cell cycle, tumour supressor protein)

Question 31

# G1 checkpoint Phosphorylation of retinablastoma

Answer 31

it can no longer bind to the dna | Allows transcription of genes that code for protein needed for DNA repli ## Footnote so Cells progress from G1 to S

Question 32

# G1 checkpoint active RB

Answer 32

- Not phosphorylated, transcription inhibition occurs - No further growth of cell, so cell cycle halts at G1

Question 33

# G1 checkpoint Inactive RB

Answer 33

Rb Has been phosphorylated, - less trancription inhibition - So growth occurs and progresses to S phase

Question 34

# what is assessed AT the G2 Checkpoint

Answer 34

sucess of dna replication and any damage to dna is assessed

Question 35

If dna damage is present during G2 checkpoint

Answer 35

Activation of several proteins including p53 is triggered

Question 36

p53

Answer 36

Can stimulate DNA repair Arrest the cell cycle Or cause cell death

Question 37

Metaphase checkpoint | controls

Answer 37

Controls progression from metaphase to anaphase ## Footnote Progression is halted until chromosomes are alligned correctly on the metaphase plate and attatched to the spindle microtubules

Question 38

Uncrontoled reduction and increase in rate of cell cycle

Answer 38

Reduction= May result in degeerative diseases Increase= may result in tumour formation

Question 39

# What is a Proto-oncogene

Answer 39

A normal gene, usually involved in the control of cell growth or divison ## Footnote It can mutate!!! To form a tumour promoting oncogene

Question 40

# Ccontrol of Apoptosis | triggered by

Answer 40

Triggered by cell death signals that can be external or internal

Question 41

Production of cell death signal molecules from | Lymphocytes and Dna damage

Answer 41

lymphocytes= Example of external death signals DNA damage= Internal

Question 42

External Death signal molecules

Answer 42

Bind to a **surface receptor protein** and trigger a protein cascacde within the cytoplasm

Question 43

What causes activation of p53 | tumour supressor protein

Answer 43

Internal death signals (dnadamage)

Question 44

All Death signals cause

Answer 44

Activation of caspases **A type of protease enzyme** | That cause destruction of the cell

Question 45

# WHat is Apoptosis essential during

Answer 45

- Development of an organism to remove cells that arent required as development progresses - or during metamorphosis

Question 46

# What happens in the ABsence of growth factors

Answer 46

Cells may initiate apoptosis