Lecture 11: The Cytoskeleton Part 1

Three kinds of filaments that make up our cytoskeleton

1. Intermediate Filaments

2. Actin Filaments

3. Microtubules

Cytoskeleton Definition

organized networks within cells that give cells structure

Polarity, meaning and what filaments are polar/non-polar

1. polarity relates to the top & bottom being the same (non polar) or not.

2. Actin & Microtubules are polar & Intermediate Filaments are non-polar

Subunits (what they are and how they’re held together)

the building blocks of each filaments, held thorough IMFS

Intermediate Filaments (Function) (TENSILE & ROPE LIKE)

prove strength and structure to the cell (MUSCLE CONTRACTION) 

• tensile and rope like

Intermediate Filaments subunit

• a tetramer 

• staggered anti-parallel tetramer of two coiled dimers 

• NON-Polar 

What gives intermediate filaments their noble strength

their side to side & lethal interactions make them tensile and rope like

The Two Types of Intermediate Filaments

• Cytoplasmic (Keratin Filaments)

• Nucelar Filaments 

Keratin Filaments (function & location)

• distributes stress between cells 

• anchored to the plasma membrane of the cell 

• The keratin filaments are linked together from cell to cell

Nuclear Filaments

• nuclear lamina

  • provide strength and support for the nuclear membrane 

Actin Filaments

• highly dynamic because subunit can be removed real easy 

• Polar 

• MONOMER is the subunit (amino & carboxyl sides) 

Microtubule Filaments

• Hollow cylinders of tubular heterodimers (alpha & beta [on top])

• highly dynamic 

MT filaments subunit

a heterodimer, made up of alpha and beta tubulin where beta tubular is on the top

Actin Filament Subunit

a monomer; single protein

Plus & Minus Ends (what do they mean)

• plus end: taste growing

• minus end: slower growing

Why do filaments (actin & MTs) have polarity

so that motor proteins have google maps (know where to go)

Motor Proteins Anatomy

• Heads that walk and tails that hold the cargo

• Some idiot named this 

Microtubule motor proteins

• dynein (-) & kinesin (+)

• dynein is nein in German which si no an negative and it goes to the negative side 

• Kinesin is like adding a phosphate which is happy happy and it goes to the positive side

How do MT motor proteins walk (what causes it)

ATP hydrolysis & exchange 

How sliding MT’s & Actin works

there is an anchor attaches o the motor protein, when the motor walks it causes the filament to slide in the opposite direction

Actin Motor Protein

• Myosin-

• Walks to the plus end 

Myosin 2

ENTIRE job is to slide actin filaments 

• dimer

• heads walk on actin

• multiple motors can assemble together to form a bipolar filament

• Can form contractile structures

• Job is to do muscle contraction