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Genetics > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

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1
Q

Roles of the cytoskeleton?

A

Mechanical- strength & shape
Transport- provide trails & highways for transport of cargo
Scaffolding
Dynamic- flexible as needs to adapt

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2
Q

What 3 types of protein make up the cytoskeleton?

A

Actin filaments, microtubules & intermediate filaments

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3
Q

Role of actin filaments?

A

Determine shape of cells surface
Necessary for whole-cell locomtion
Drive pinching of one cell into two (cytokinesis)

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4
Q

Where are actin filaments found?

A

Highest conc in cell periphery, plasma membrane (provide shape to lipid bilayer), anchor membrane proteins

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5
Q

What are the cell-surface projections on actin filaments?

A

Lamelipodia & filipodia
Examples: sterocilia on ears, micovilli on epithelial cells (increase SA)

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6
Q

How big is actin and what ends does it have?

A

42 kd
Fast growing + end and slow growing - end
Most cells + end is toward edge of cell

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7
Q

What does actin interact with?

A

Myosin

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8
Q

What is myosin?

A

Enzymes that convert chemical energy into movement

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9
Q

How does myosin/actin work?

A

Myosin bind actin in ATP sensitive fashion
Myosin II slides actin filaments past each-other to produce power contraction of the contractile ring or to produce cell migration

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10
Q

What are myosin & actins role in muscle?

A

Myosin: thick filaments
Actin: thin filaments

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11
Q

What are microtubules?

A

Polymers of tubular molecules
Found in cytoplasmic array that extends to cell periphery
Form mitotic spindles during cell division

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12
Q

Role of microtubules?

A

Determine positions of membrane enclosed organelles
Direct intracellular transport
Form mitotic spindle

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13
Q

Role of microtubule in mitosis?

A

Microtubule network disassembled after mitosis, tubulin subunits are reassembled into spindle
Spindle responsible for cytokinesis

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14
Q

What is the primary role of microtubules?

A

Serve as tracks along which membrane bound vesicles are moved, including organelles such as mitochondria and secretory vesicles destined for exocytosis

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15
Q

What do microtubules consist of?

A

Produced by self-assembly of a subunit
Heterodimer of 1a tubulin & 1b tubulin (interact to form a protofilament)
13 protofilaments line up side by side forming a hollow tube

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16
Q

Mictotubule ends?

A

Fast growing + (near cell surface)
Slow growing - (near MTOC)
Radial array extending from a single site
MICROTUBULE ORGANISING CENTRE- normally near the nucleus

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17
Q

Are microtubules always the same length?

A

No. Constantly grow and shorten

18
Q

Do microtubules have proteins?

A

Yes. Microtubule associated proteins (MAPs) can stabilise microtubules or cross-link with other microtubules, microfilaments and intermediate filaments

19
Q

What is a centriole?

A

Cylinder of 9 triplets of microtubules

20
Q

What is a centrosome?

A

2 centrioles

21
Q

What is the role of a centrosome?

A

Duplicated before a cell divides
Act as MTOC during interphase and become centre of spindle pole during mitosis

22
Q

What are cilia?

A

Microtubules which function as motile whips and sensory devices on the surface of the cell
Move dust in nose

23
Q

What is cilias role?

A

Tracks for transport of materials down neuronal axons

24
Q

What are flagella?

A

Long hair-like structures
Cell movement- sperm
Usually one or a few

25
Q

What do flagella and cilia have in common?

A

Structure, 9+2 array, 9 pairs of microtubules arranged in a circle plus 2 additional microtubules in the centre of the ring
Function, dyneins move along both causing them to beat

26
Q

What is kinesin?

A

Many members
Responsible for moving vesicle’s towards the plus end of microtubules from the centre of the cell to the plasma memebrane
Important for spindle function during mitosis

27
Q

What is cytoplasmic dyenin?

A

Moves cargo exclusively toward - end of microtubules (so back towards centre)

28
Q

What is dynein used in?

A

Transmission of nerve impulses, hormone secretion, recycling of membrane

29
Q

How do genetic diseases affect cilia?

A

Dynein mutation, cillia dysfunciton- respiratory illness & sperm immotility
situs inversus

30
Q

How do kinesin mutations affect people?

A

Neurological conditions
e.g KIF1A mutations

31
Q

Differences betwen actin and microtubules?

A

Actin: motors are myosin
Mictoubules: dynenin and kinesin

32
Q

Similarities between actin and microtubules?

A

Structurally asymmetrical subunits
Both function as suitable tracks for molecular motors that move preferentially in one direction

33
Q

What are intermediate filaments?

A

Formed from a large number of different proteins
Provide mechanical strength

34
Q

Some examples of intermediate filaments?

A

Keratins: epithelial
Vimentin: fibroblasts
Desmin: heart
Neurofilament: nervous system
Lamins: nucleus

35
Q

Genetic diseases in intermediate filaments?

A

Keratins: liver disease
Neurofilaments: ALS
Lamins: progeria

36
Q

What do intermediate filaments do?

A

Line inner surface of nuclear envelope
In cytosol, twisted into cable that can hold epithelial cell sheets together
Help nerve cells to extend long and robust axons
Allow us to form strong appendages such as hair and fingernails

37
Q

Do intermediate filaments self-assemble?

A

Yes but no polarity

38
Q

Do intermediate filaments have associated proteins?

A

Yes but no motors

39
Q

What do intermediate filaments attach to?

A

Desmososmes and hemidesosomes
These then attach cells to neighbouring cells or the extracellular matrix

40
Q

How big are the 3 elements?

A

Actin: 8nmn, bead necklace
Tubulin: 25nm, hollow tube
Intermediate: 10nm, rope

41
Q

What do cytoskeleton filaments act with?

A

Hundreds of accessory proteins

Genetics (6 decks)

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