1.5 - Protein control of cell division

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Cytoskeleton

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Biology

32 Terms

1

Cytoskeleton

Network of different types of proteins that extends throughout the cytoplasm. The cytoskeleton gives mechanical support and shape to cells.​

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2

Microtubules

Make up the cytoskeleton. They are composed of hollow straight rods made of globular proteins called tubulins.

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3

Role of microtubules

Govern the location and movement of membrane-bound organelles and other cell components​.

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4

Centrosome (microtubule organising centre/MTOC).​

Where microtubules radiate from

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5

Role of microtubules in cell division

Microtubules form spindle fibres which are active during cell division. Cell division requires the remodelling of a cell's cytoskeleton

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6

Polymerisation and depolymerisation

Formation and breakdown of microtubules involves the build up and break down of tubulin

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7

Two main phases of the cell cycle

interphase and mitotic phase (M phase)

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8

The phase in which a cell spends the majority of its time

Interphase

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9

Three parts of interphase

G1, S, G2

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10

The two processes that occur during the M phase

Mitosis and Cytokinesis

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11

The stages of mitosis

Prophase, metaphase, anaphase and telophase

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12

Cytokinesis

The division of the cytoplasm

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13

Prophase

Replicated chromosomes condense (become shorter and fatter) and appear as pairs of identical sister chromatids. ​ Centrosomes move apart and microtubules radiate out from them to form spindle fibres.​ Nuclear membrane is broken down.

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14

Metaphase

Multiple spindle fibres become attached to each sister chromatid. ​ Replicated chromosomes are aligned at the equator of the spindle fibres that are attached to them. This position is called the metaphase plate.

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15

Anaphase

Proteins holding the sister chromatids together are degraded.​ Sister chromatids separate.​ Spindle fibres attached to each of the daughter chromosomes shorten to pull them to opposite poles of the cell.

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16

Telophase

Chromosomes arrive at each pole of the cell and decondense (unravel). ​ A new nuclear membrane forms around each group of chromosomes, forming daughter nuclei.

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17

Checkpoints

Critical control points where stop and go ahead signals regulate the cycle.​

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18

Cyclin

Proteins that accumulate as the cell size increases during G1.​

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19

Cyclin-dependent kinases (Cdks)

Regulatory proteins that are activated by cyclin. Active Cdks cause the phosphorylation of proteins that stimulate the cell cycle.

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20

G1 Checkpoint

Progression occurs at this checkpoint if a sufficient threshold of phosphorylation is reached.​ If an insufficient threshold is reached then the cell is held at the checkpoint.

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21

Retinoblastoma

A transcription factor phosphorylated by the G1 Cdks. This allows DNA replication in the S phase.

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22

G2 checkpoint

At this checkpoint, the success of DNA replication and any damage to DNA is assessed​.

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23

DNA damage

This triggers the activation of several proteins, include p53​ This can

  • Stimulate DNA repair​

  • Arrest the cell cycle​

  • Cause cell death

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24

M phase Checkpoint

A checkpoint that controls progression from metaphase to anaphase. Spindle fibre assembly is checked for.

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25

The role of the cell cycle

Regulates the growth and replacement of genetically identical cells throughout the life of the organism. ​

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26

Uncontrolled reduction in the rate of the cell cycle

This leads to degenerative diseases such as Alzheimer's or Parkinson's.

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27

Uncontrolled increase in the rate of the cell cycle

This leads to tumour formation

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28

Proto-oncogene

A normal gene, usually involved in the control of cell growth or division, which can mutate to form a tumour-promoting oncogene

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29

Apoptosis

This is triggered by cell death signals that activate inactive forms of DNAase and caspases (type of proteinase).​​ These enzymes then destroy the cell.

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30

Cell death signals outwith the cell

Cell death signal binds to a surface receptor protein to activate a protein cascade, resulting in active caspases.​

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31

Cell death signals within the cell

DNA damage results in the presence of p53 which can activate a caspase cascade​

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32

Importance of apoptosis

​ It is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis​.

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