PHGY 170 - Learning Outcomes Assignment 8
1. What are the functions of the cytoskeleton? (2 points)
The cytoskeleton is a network made up of structural proteins that is found in all types of cells.
One function of the cytoskeleton is allowing common cellular functions, like signalling and
vesicular transport to occur, and giving some cells their unique properties like cell motility. The
cytoskeleton is also responsible for defining the shape of the cell and distributing cellular
contents.
2. What are the roles of the intermediate filaments, microtubules, and actin filaments
within cells? (3 points)
Intermediate Filaments:
● These filaments supply the strength to cells that allows them to resist changes of shape,
providing mechanical strength to cells.
Microtubules:
● Support trafficking within cells (movement of proteins, vesicles, and cellular organelles
in the cytoplasm).
● They define how components are trafficked in the cytoplasm, and define routes for cargo
travel.
Actin Filaments:
● Form a strong network that contributes to the structure of cells and large scale movement
like muscle contraction.
3. Compare and contrast the assembly of intermediate filaments, microtubules, and actin
filaments. (6 points)
Intermediate Filaments:
2 coiled monomers join together to form a dimer, 2 dimers join together to form a tetramer.
● Stage 1: until-length filaments are formed by 8 tetramers joining together.
● Stage 2: these unit-length filaments join together forming immature filaments.
● Stage 3: intermediate filament compacts forming a mature filament.
Microtubules:
In contrast with intermediate filaments, assembly is more organized and doesn’t happen
spontaneously. Requires a number of proteins and happens in the microtubule organizing centres
(MTOCs).
● Stage 1: formation of microtubules from a-b tubulin dimers is dynamic.
● Stage 2: if the polymer reaches a critical length, they’ll continue to grow.
1. What are the functions of the cytoskeleton? (2 points)
The cytoskeleton is a network made up of structural proteins that is found in all types of cells.
One function of the cytoskeleton is allowing common cellular functions, like signalling and
vesicular transport to occur, and giving some cells their unique properties like cell motility. The
cytoskeleton is also responsible for defining the shape of the cell and distributing cellular
contents.
2. What are the roles of the intermediate filaments, microtubules, and actin filaments
within cells? (3 points)
Intermediate Filaments:
● These filaments supply the strength to cells that allows them to resist changes of shape,
providing mechanical strength to cells.
Microtubules:
● Support trafficking within cells (movement of proteins, vesicles, and cellular organelles
in the cytoplasm).
● They define how components are trafficked in the cytoplasm, and define routes for cargo
travel.
Actin Filaments:
● Form a strong network that contributes to the structure of cells and large scale movement
like muscle contraction.
3. Compare and contrast the assembly of intermediate filaments, microtubules, and actin
filaments. (6 points)
Intermediate Filaments:
2 coiled monomers join together to form a dimer, 2 dimers join together to form a tetramer.
● Stage 1: until-length filaments are formed by 8 tetramers joining together.
● Stage 2: these unit-length filaments join together forming immature filaments.
● Stage 3: intermediate filament compacts forming a mature filament.
Microtubules:
In contrast with intermediate filaments, assembly is more organized and doesn’t happen
spontaneously. Requires a number of proteins and happens in the microtubule organizing centres
(MTOCs).
● Stage 1: formation of microtubules from a-b tubulin dimers is dynamic.
● Stage 2: if the polymer reaches a critical length, they’ll continue to grow.
