Unit 1 KA 5 ✓

Question 1

What are Eukaryotic cells?

Answer 1

Eukaryotic cells are cells that have an internal network called a cytoskeleton

NOTE: They also have a clearly defined nucleus

Question 2

What is the Cytoskeleton?

Answer 2

The cytoskeleton is an internal network that provides a cell with mechanical support and shape. It is made up of microtubules

Question 3

What are Microtubules?

Answer 3

Microtubules are polymers composed of the monomer tubulin. They make up the cytoskeleton

Question 4

What is the Microtubule organising centre? (MTOC)

Answer 4

The MTOC is also known as the centrosome or cell poles of a cell. Microtubules radiate out from the MTOC

Question 5

What is Polymerisation?

Answer 5

Polymerisation is building up (depolymerisation is breaking down)

Question 6

What is the Kineticore of a chromosome?

Answer 6

The kineticore of a chromosome is the middle region where spindle fibres attach

Question 7

What is the Cell cycle?

Answer 7

The cell cycle is made up of phases that a cell goes through in its lifetime. It is made up of two parts, interphase and the mitotic phase

Question 8

What is Mitosis?

(Why is it important?)

Answer 8

Mitosis is the process whereby a cell divides into two identical daughter cells. It is important for the growth and repair of tissues/cells and it also maintains the cell’s diploid chromosome complement

(The first stage of the mitotic phase)

Question 9

What is Interphase?

Answer 9

Interphase is the first stage of the cell cycle, it prepares the cell for replication. Interphase accounts for the majority of the time spent in the cell cycle. It contains 3 sub-phases.

(G1 - Growth phase, S - DNA replication, G2 - Further growth phase)

Question 10

What is the Mitotic phase?

Answer 10

The Mitotic phase (M) is the phase where the cell undergoes mitosis then cytokinesis

Question 11

Phases of mitosis (PMAT):

What is Prophase?

Answer 11

Prophase is the stage of mitosis where the DNA condenses and the nuclear membrane breaks down. Spindle fibres extend out by polymerisation and attach to the chromosomes

Question 12

Phases of mitosis (PMAT):

What is Metaphase?

Answer 12

Metaphase is the stage of mitosis where chromosomes align at the metaphase plate (equator)

Question 13

Phases of mitosis (PMAT):

What is Anaphase?

Answer 13

Anaphase is the stage of mitosis where spindle fibres shorten by depolymerisation and seperate the sister chromatids, pulling the chromosomes to opposite poles

Question 14

Phases of mitosis (PMAT):

What is Telophase?

Answer 14

Telophase is the stage of mitosis where the chromosomes decondense and nuclear membranes form around them

(Opposite of prophase)

Question 15

What is Cytokinesis?

Answer 15

Cytokinesis is the second part of the mitotic phase. The cytoplasm is seperated into two identical daughter cells

Question 16

In terms of monitoring cell division:

What are Checkpoints?

Answer 16

Checkpoints are used to ensure the division of a cell progresses in the right way at the right time. They determine whether a cell progresses onto the next stage or undergoes cell cycle arrest/apoptosis

(Apoptosis - programmed cell death)

Question 17

Cell division checkpoint 1/3:

What does the G1 checkpoint check?

Answer 17

The G1 checkpoint checks for DNA damage, growth factors and nutrients

Question 18

Cell division checkpoint 2/3:

What does the G2 checkpoint check?

Answer 18

The G2 checkpoint checks for DNA damage after replication and cell size

Question 19

Cell division checkpoint 3/3:

What does the M checkpoint check?

Answer 19

The M checkpoint checks that chromosomes are properly attached to spindle fibres, and they are aligned at the metaphase plate (equator)

Question 20

What are Cyclin proteins?

Answer 20

Cyclin proteins are proteins which accumulate during the G1 growth phase and bind to CDK’s to form activated CDK complexes

(CDK - Cyclin Dependant Kinases)

Question 21

What are Cyclin dependant kinases? (CDK’s)

Answer 21

CDK’s are a type of kinase that form an activated complex when bound to cyclin. Activated CDK’s add a phosphate group (phosphorlyation) to retinablastoma (Rb)

Question 22

What is Retinablastoma? (Rb)

Answer 22

Retinablastoma (Rb) is a tumour supressor that can inhibit the transcription of genes essential for DNA replication. When Rb is sufficiently inhibited by phosphorylation, the transcription of genes is allowed and the cell cycle will progress

Question 23

What is a p53 protein?

Answer 23

p53 is a protein that can stimulate DNA repair, arrest the cell cycle or cause cell death (apoptosis) at the G2 checkpoint

NOTE: Apoptosis is programmed cell death

Question 24

In terms of uncontrolled cell division:

Why is a decrease in cell division harmful?

Answer 24

A decrease in cell division is harmful as it could cause a degenerative disease

e.g. Alzheimers

Question 25

# In terms of uncontrolled cell division: Why is an **increase** in cell division harmful?

Answer 25

An increase in cell division is harmful as a tumour could form | e.g. Cancer

Question 26

What is a **Proto-oncogene**?

Answer 26

A proto-oncogene is a normal gene which is usually involved in controlling cell growth and division. However it can mutate to form a *tumour promoting oncogene* ## Footnote NOTE: Remember, the oncology ward in a hospital treats cancer and tumours

Question 27

What signals promote apoptosis?

Answer 27

Apoptosis is promoted by internal signals such as DNA damage and external signals such as a lack of growth factors or the production of death signal molecules (produced by lymphocytes)

Question 28

What are **Caspases**? | (What activates a caspase cascade?)

Answer 28

Caspases are types of protease enzymes activated by apoptosis signals, they break down proteins - destroying the cell

Question 29

What is **Apoptosis**? | (Why is it essential?)

Answer 29

Apoptosis is programmed cell death. However its also essential during development or metamorphosis as they remove cells no longer required | NOTE: Tadpoles undergo metamorphisis to become frogs. ## Footnote NOTE: Think about how fingers form, people with webbed fingers lacked apoptosis during development