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Human Sciences > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

What is pinocytosis?

A

Ingestion of liquids by budding of small vesicles

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2
Q

What is phagocytosis?

A

Ingestion of whole cells and large insoluble particles

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3
Q

Outline endocytosis

A
  1. Coates vesicles formed from coated pits
  2. Vesicles are uncoated
  3. Vesicles fuse to endosomes
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4
Q

How are secondary lysosomes formed?

A

Joining of endosomes and primary lysosomes from phagocytosis of bacteria

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5
Q

Where would you find a targeting sequence?

A

In a protein destined for a certain organelle

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6
Q

What are the functions of the cytoskeleton?

A
  • Integration of compartments (membrane traffic) and response to cell signals
  • Organelle distribution
  • Cell motility and division
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7
Q

What are the main features of polymers in the cytoplasm?

A
  • Dynamic
  • Rapid assembly and dissassembly
  • May be polar
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8
Q

What is the protein concentration in cytoplasm?

A

~20%

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9
Q

What are the main properties of cytoplasm?

A
  • non-Newtonian- can behave like a solid
  • non-uniform- microdomains exist
  • resists sudden impacts, melts under slow persistent shear
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10
Q

What diameters are microtubules, microfilaments and intermediate filaments?

A

Microtubules- 25nm
Microfilaments- 7nm
Intermediate filaments- 10nm

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11
Q

How easily deformed and ruptured are individual actin filaments, microtubules and vimentin networks (intermediate filaments)

A

Actin filaments- easily d and r
Microtubules- rigid- easily r not d
Vimentin- easily d not r

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12
Q

What reagents can be used to study the cytoskeleton?

A
  • Antibodies- markers for proteins

* Antibiotics- target elements of cytoskeleton

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13
Q

Which antibiotics target microtubules?

A

Colchicine and taxol

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14
Q

Which antibiotics target F-actin?

A

Phalloidin and cytochalasins

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15
Q

What instrumentation can be used to study the cytoskeleton?

A

Low-light digital videomicroscopy

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16
Q

What genetic manipulations can be used to study the cytoskeleton?

A
  • Gene tagging (GFP)

* Modification of gene expression

17
Q

What are the functions of microtubules?

A 
• Cell shape and polarity
• Cell organisation and positioning of organelles
• Cell division
• Cell motility:
-Intracellular transport
-Cilia and flagella
-Sensory systems
18
Q

Outline the composition of microtubules

A
  • Tubulin- alpha beta heterodimer
  • Assemble head to tail- protofilaments
  • 13 protofilaments make up the wall of a microtubule
  • Exist in dynamic equilibrium- added to one end, removed from other
19
Q

Where do microtubules arise and how do they assemble?

A
  • Arise from centrosome- microtubule organising centre (MTOC)
  • Assemble with +be end (beta) distal to centrosome
20
Q

What is a centrosome?

A

Pair of centrioles enclosed in shell of pericentriolar material (contains lambda tubulin)

21
Q

What do low temperatures do to microtubules?

A

Reversibly disassembles then

22
Q

What effect does cochicine have on a cell?

A

Depolymerises cytoplasmic microtubules, therefore causes organelle dispersal
(As microtubules determine the 3D organisation of organelles)

23
Q

What are microfilaments made up of?

A

Dynamic polymer of G-actin monomers

24
Q

What effect does cytochalasin have on actin filaments?

A

Depolymerises them

25
Q

What effect does phalloidin have on actin filaments?

A

Stabilises them

26
Q

How abundant is actin in a cell?

A

Most abundant protein

10-15%

27
Q

Outline microfilament assembly?

A
  • Assembly at +ve end, disassembly at -ve

* ATP dependant- one ATP for each monomer lost from -ve

28
Q

What are actin binding proteins?

A

Regulate actin filament function

Eg. In the brush border actin filaments are cross linked by villin

29
Q

Why are intermediate filaments stable during interphase?

A

No cytoplasmic pool of subunits and filaments

30
Q

What protein composition do intermediate filaments have?

A

Alpha helix rich
Alpha type fibrous proteins
(Not globular like mf and mt)

31
Q

Describe intermediate filament function

A
  • Very heterogenous and tissue specific

* Mechanical integrators of cells into tissues

32
Q

Describe the composition of intermediate filaments

A

Monomers are an alpha helix rod and two globular heads

4 monomers form a tetramer filament

33
Q

What are four intermediate filament proteins and where are they used?

A
  1. Lamin- nuclear lamina
  2. Vimentin- cells of mesenchymal origin
  3. Keratin- epithelial cells and derivatives
  4. Neurofilaments- neurons
34
Q

Where are intermediate filaments found in epithelial cells?

A
  • Keratin filaments- structure
  • Nuclear lamina
  • Dermosomes (join cells together)
  • Hermidermosones (to basement membrane)
  • Basement membrane
35
Q

What makes up a cytoskeletal motor?

A

An ATPase and a linear polymer with intrinsic polarity

36
Q

Which ATPases pair with which linear polymers to form cytoskeletal motors?

A

Myosin with F-actin

Dynein and kinesin with microtubules

37
Q

What are cross-bridge cycles?

A

Vectorial movement- direction determined by polarity

Step distance ~8nm

Human Sciences (8 decks)

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