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AH Biology > Protein Control of Cell Division > Flashcards

Protein Control of Cell Division Flashcards

(59 cards)

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1
Q

What is the cytoskeleton?

A

Network of protein fibres that extend throughout the cytoplasm in all eukaryotic cells

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2
Q

Give some functions of the cytoskeleton

A

Provide mechanical support so cell maintains shape
Provides anchorage for many organelles
Allow the whole cell to move
Enable organelles within the cell to move

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3
Q

What are the three main components of the cytoskeleton?

A

Microtubules, intermediate filaments, actin filaments

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4
Q

Describe what actin mirofilaments are made up of?

A

Polymers of the soluble globular protein actin

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5
Q

What is the width of microfilaments?

A

2 nano metres

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6
Q

What are actin microfilaments responsible for?

A

Cellular movements, such as contraction during cytokineses

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7
Q

Describe intermediate filaments and give their width

A

Formed from fibrous proteins
Rope like in structure
10 nano metres in diametes
Consist of two pairs of monomers wrapped around each other

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8
Q

What is the function of intermediate filaments?

A

Give the cell its mechanical strength/support

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9
Q

What are microtubules made of?

A

Polymers of a dimer consisting of alpha tubulin and beta tubulin

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10
Q

What is the width of microtubules?

A

25 nano metres

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11
Q

How is the length of microtubules controlled?

A

Addition or removal of tubulin at the ends of the microtubules

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12
Q

What is the function of microtubules?

A

Govern the location and movement of membrane bound organelles

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13
Q

Where do microtubules radiate from?

A

Microtubules Organising Centre (MTOC)

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14
Q

Where is the MTOC located and what does it contain?

A

Near the nucleus

Centrosome

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15
Q

What are the three roles of microtubules in cell division?

A
  1. The aster at each centrosome ensures that the cell division apparatus is located at the correct position
  2. Spindle microtubules attach to kinetechore proteins at the centrosomes of each chromatid
  3. Microtubules attach to microtubules from the opposite centrosome
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16
Q

How are the chromatids seperated during cell division?

A

Disassembly of the microtubules at the kinetchores

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17
Q

What are the two phases of the cell cycle?

A

Interphase and Mitosis

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18
Q

What are the three phases of interphase?

A

G1, S, G2

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19
Q

What happens in the G1 stage of interphase?

A

First growth stage

Cell makes copies of new proteins and organelles

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20
Q

In what stage of interphase does DNA replication occur?

A

S

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21
Q

What occurs in the G2 phase of cell division?

A

Second growth phase

Cell makes more proteins and copies organelles in prep for mitosis

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22
Q

What are the five stages of mitosis?

A 
Prophase
Metaphase
Anaphase
Telophase
Cytokenesis
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23
Q

What happens during prophase?

A

Chromosomes condense
Each chromosomes is composed of two chromatids
Microtubules start to assemble to the spindle fibres
Some spindle fibres attach to the kinetechore

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24
Q

In what stage are the sister chromatids pulled apart?

25
What happens in Telophase?
Seperated chromosomes are pulled to opposite poles Chromosomes form daughter nuclei Chromosomes start to uncoil and nucleur membrane forms
26
Where do chromosomes line up in metaphase?
Metaphase plate at the equator of the cell
27
What happens during metaphase?
Chromosomes line up on the metaphase plate at equator of cell Movement acheived by assembly/diassembly of tubulin dimers
28
How do spindle fibres contract and expand?
Addition and removal of dimers onto the spindle fibres
29
What is Cytokenesis?
Division of the cytoplasm to form two daughter cells
30
What is the mitotic index?
Percentage of cells undergoing mitosis in the sample
31
What may be indicated from an abnormally high mitotic index in a sample?
Developing tumour
32
What can an uncontrolled reduction in the rate of the cell cycle cause?
Degenerative diseases
33
What is one of the causes of cancer?
Uncontrolled increase in the rate of the cell cycle
34
Where are the checkpoints in the cell cycle?
G1, G2, M
35
What are checkpoints?
Critical control points where stop and go-ahead signals regulate the cycle
36
What is checked at the G1 checkpoint?
Cell size is monitored
37
Which checkpoint regulates entry to G0/S phase?
G1 checkpoint
38
What is assessed at the G2 checkpoint?
Success of DNA replication
39
Describe the M checkpoint
occurs during metaphase monitors chromosome alignment makes sure each daughter cell receives one chromatid from each chromosome controls entry to anaphase
40
what accumulates as cell size increases in the g1 phase?
cyclins
41
What do cyclins combine with?
Cyclin Dependant Kinases
42
What does the binding of cyclin and CDKS form?
Mitosis Promoting Factor
43
What do active CDKs do?
Phosphorylate target proteins that stimulate the cell cycle
44
What is Rb?
Restinoblastoma protein is a transcription protein important at the G1 checkpoint
45
What is Rb involved with?
Production of proteins required for DNA replication in the S phase
46
What phosphorylates Rb?
CDKs
47
What happens when the activity of CDKs reaches a sufficent threshold?
Each Rb has been phosphorylated 14 times and so can no longer bind to the transcription factors, allowing the cell to progress past the G1 checkpoint into S
48
What is p53?
A transcription factor
49
What are the three functions of p53?
Stimulate DNA Repair Arrest the cell cycle Trigger apoptosis
50
What happens if DNA damage has occured?
p53 causes the expression of genes to stimulate DNA repair, arrests the cell cycle
51
What happens if DNA repair is not successful?
p53 instructs the cell to kill itself
52
What is apoptosis?
Programmed cell death
53
What is apoptosis triggered by?
Cell death signals
54
Where can cell death signals come from?
Outside the cell or inside the cell
55
Give an example of a cell death signal that originates from outside the cell
Lymphocyte | Natural Killer Cell
56
What happens in the case of an external cell death signal?
Ligand binds to a receptor protein Causes a conformational change on the cytoplasmic side Acts as a signal transduction and activates a protein cascase that produces caspases
57
When may a cell death signal originate from inside the cell?
When DNA damage is detected | Absence of cell growth factors
58
How is a caspase cascade initiated?
Caspases must be activated Inactive proteinases and DNAases are activated Initiator caspases activate executioner caspases Degrade cellular components
59
What is the cause of the fact that the cell breaks into many small vesicles?
Lack of intact cytoskeleton

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