Lecture 1 - The Cytoskeleton Flashcards

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1
Q

State the diameters of the 3 filaments.

A

MFs: 7-9nm
MTs: 25nm
IFs: 10nm.

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2
Q

State the general structure of the 3 different filaments.

A

MFs: double helix of actin monomers.
MTs: hollow tube of tubulin dimers.
IFs: fibre composed of various of IF proteins, e.g. keratins.

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3
Q

State the role of the 3 different filaments.

A

MFs: cell movement, muscle contraction, cytokinesis.
MTs: scaffold, provides ‘track’ for the transport of vesicles/organelles, spindle fibres.
IFs: tensile strength.

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4
Q

What are lamellipodia and filopodia?

A

These are membrane protrusions that form at the leading edge and are rich in actin filaments.

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5
Q

What are the differences between lamellipodia and filopodia?

A

Lamellipodia are broader extensions typical of rapidly moving cells. Filopodia are thinner and are typical of slower moving cells.

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6
Q

Moving cells must attach to external surfaces they are travelling along using…

A

Focal adhesions, which are formed through integrins.

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7
Q

Give a brief description of the structure of globular actin.

A
  • Globular protein, 2 lobes, each lobe has 2 domains.
  • Domain I and III are connected by a hinge region, allowing them to move relative to one another. Forms a nucleotide binding cleft.
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8
Q

At which end is Cc lower?

A

Cc is lower at the (-) end. More likely to lose monomers.

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9
Q

How is the process of treadmilling maintained?

A

The Cc must be between that for the (+) end and (-) end.

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10
Q

Is actin’s ATPase activity higher in its polymerised or unpolymerised form?

A

Polymerised. Therefore, the longer the G-actin has been part of the filament, the more likely it is to be ADP bound.

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11
Q

The ADP-bound form has a reduced affinity for its neighbouring subunits. What does this mean?

A

More likely to dissociate.

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