1.5 Protein Control of Cell Division

Question 1

What are Chromosomes made from?

Answer 1

Threadlike structures composed of 2 identical chromatids

Question 2

What is the cytoskeleton?

Answer 2

Network of protein fibres inside a cell, it extends from the nucleus to the plasma membrane

Question 3

What does the cytoskeleton do?

Answer 3

Gives mechanical support and shape to cells and consists of different protein structures

Question 4

What are microtubules?

Answer 4

Hollow cylinders composed of tubulin (alternating alpha and beta tubulin) which radiate from the MTOC aka centrosome
Formed by polymerisation and depolymerisation of tubulin

Question 5

What do microtubules do?

Answer 5

Movement of whole cells, movement of organelles and chromosomes, spindle fibres formed which are active during cell division

Question 6

What is a chromatin?

Answer 6

Complex of DNA molecules and many associated proteins within chromosomes

Question 7

What does cell division allow?

Answer 7

Multicellular organisms to grow, replace dead cells and repair tissue

Question 8

What is the product of the cell cycle?

Answer 8

Two genetically identical daughter cells

Question 9

What is the cell cycle regulated by?

Answer 9

A control system which responds to intracellular and extracellular signals

Question 10

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

Answer 10

Tumour formation

Question 11

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

Answer 11

Degenerative disease e.g Alzheimers

Question 12

What does the cell cycle consist of?

Answer 12

Interphase and Mitotic (M) phase

Question 13

What is the interphase?

Answer 13

Period of cell growth and DNA replication

Question 14

What is Interphase divided into?

Answer 14

3 sub-phases called G1, S phase, G2

Question 15

What is the G1 phase of Interphase?

Answer 15

It is a growth period where proteins and organelles are synthesised, the cell is active and carrying out metabolic processes

Question 16

What is the S phase of Interphase?

Answer 16

Nuclear DNA replication, cell continues to grow and copies its chromosomes in prep for mitosis, each chromosome becomes 2 sister chromatids

Question 17

What is the G2 phase of Interphase?

Answer 17

Second growth period during which proteins and organelles are synthesised

Question 18

What are the 2 stages of the Mitotic (M) phase?

Answer 18

Mitosis and Cytokinesis

Question 19

What is Mitosis?

Answer 19

The nucleus and its contents divide

Question 20

What is Cytokinesis?

Answer 20

The separation of the cytoplasm into daughter cells

Question 21

What are the 4 stages of Mitosis?

Answer 21

Prophase, Metaphase, Anaphase, Telophase (PMAT)

Question 22

What occurs during Prophase?

Answer 22

DNA condenses into chromosomes of 2 sister chromatids, nuclear membrane breaks down and spindle microtubules extend from MTOC by polymerisation and attach to chromosomes via kinetochores in the centromere

Question 23

What occurs during Metaphase?

Answer 23

Chromosomes are aligned at metabolic plate

Question 24

What occurs during Anaphase?

Answer 24

Spindle microtubules shorted by depolymerisation which separates sister chromatids, and the chromosomes are pulled to opposite poles

Question 25

What occurs during Telophase?

Answer 25

The chromosomes decondense and nuclear membranes are formed around them, cytokinesis also takes place during this period

Question 26

What is the Mitotic index?

Answer 26

The percentage of cells in a sample undergoing mitosis

Question 27

What are checkpoints used for?

Answer 27

Assess the cells condition during the cells cycle, progression to the next phase will be halted until certain requirements are met

Question 28

What are the 3 checkpoints?

Answer 28

Near the end of G1, at the end of G2 and in metaphase of the M phase

Question 29

What are Cyclin proteins in the cell cycle?

Answer 29

Accumulate during cell growth and are involved in regulating the cell cycle, they combine with and activate CDKs

Question 30

What are active cyclin-CDKs?

Answer 30

Complex which phosphorylate proteins that regulate progression through the cell cycle (sufficient phosphorylation is required for progression)

Question 31

What is the G1 checkpoint?

Answer 31

Phosphorylation by G1 c-CDKs inhibits Rb thus transcription of genes that code for proteins needed for DNA replication takes place

Question 32

What are Retinoblastoma proteins?

Answer 32

Retinoblastoma protein (Rb) is a tumour-supressor as it inhibits gene transcription coding for proteins needed for DNA replication.

Question 33

What occurs at the G2 checkpoint?

Answer 33

The success of DNA replication and DNA damage is assessed.

Question 34

What does DNA damage cause?

Answer 34

Activation of p53 proteins which results in either stimulation of DNA repair, arrest the cell cycle, cell death (apoptosis)

Question 35

What occurs at the M checkpoint?

Answer 35

Controls progression from metaphase to anaphase. Progression is conditional on the chromosomes being correctly aligned on the metaphase plate and attached to spindle microtubules

Question 36

What is a proto-oncogene ?

Answer 36

Normal gene usually involved in control of cell growth or division, it can mutate to form a tumour promoting oncogene which can cause the cell to divide in an uncontrolled manner

Question 37

What is apoptosis?

Answer 37

Programmed cell death

Question 38

What can trigger apoptosis?

Answer 38

Cell death signals which are internal (DNA damage) or external (death signal molecules from lymphocytes)

Question 39

What do internal death signals cause?

Answer 39

Activation of p53 tumour-suppressor protein

Question 40

What do external death signal molecules do?

Answer 40

Bind to a surface receptor protein, triggering a protein cascade within the cytoplasm

Question 41

What are Caspases?

Answer 41

A type of protease molecule which is activated by internal and external death signals

Question 42

What are protease molecules?

Answer 42

Enzymes which destroy the cell by triggering the degradation of any protein molecule

Question 43

Why is apoptosis important?

Answer 43

Essential during development to remove cells which are no longer required or during metamorphosis (e.g webs between toes in embryos)