Lesson 10: Cytoskeleton
Function of cytoskeleton
- Cell movement
- Cell shape and polarity
- Cell adhesion and tissue structure
- Intracellular movement
- Support specialised structures eg. cilia
3 layers of the cytoskeleton
- They are protein polymers
- 1. Actin (microfilaments) = 7nm
- 2. Intermediate filaments = 10nm
- 3. Microtubules = 20nm
- Associated proteins bind to the filaments. The wide variety of associated proteins
allows these basic structural filaments to perform their different and diverse functions.
Actin
- Filaments are called f actin (filamentous actin)
- The filaments are polymers of individual actin proteins called G actin (globular actin)
- The combined weight of the filamentous actin and globular actin is 5% of the total
protein of a typical cell
- Shape is a polarised double helix
- It has an asymmetric shape and gives polarity to the filament. The top is positive and
the bottom of the tail is negative.
- Regulates movement of entire cells (eg, neutrophil engulfing bacteria)
- Regulates growth of nerve processes
-
Assembly and growth of the actin filament
- Requires ATP which is bound to each G actin monomer. More ATP is bound to the
plus end of the monomer
- Filaments are very dynamic as they can extend and contract frequently.
- Monomers can be added and removed from both ends of the polymer.
- When the monomer has been added and incorporated into the filament structure then
the ATP is hydrolysed to ADP and there is a release to and an inorganic phosphate is
released.
Function of actin
- Mechanical support eg, cochlea cells in ear
- Changing and supporting shape of cells eg, biconcave red blood cell
- Cell motility eg, muscle cells
- Actin binding proteins modulate polymerisation dynamics and function
- Actin binding proteins allow actin filaments to interact with many different cytoplasmic
proteins and thereby actin’s diverse and essential roles
- They also provide support and can be found beneath the plasma membrane
- Maintain cell shape in erythrocytes
Function of cytoskeleton
- Cell movement
- Cell shape and polarity
- Cell adhesion and tissue structure
- Intracellular movement
- Support specialised structures eg. cilia
3 layers of the cytoskeleton
- They are protein polymers
- 1. Actin (microfilaments) = 7nm
- 2. Intermediate filaments = 10nm
- 3. Microtubules = 20nm
- Associated proteins bind to the filaments. The wide variety of associated proteins
allows these basic structural filaments to perform their different and diverse functions.
Actin
- Filaments are called f actin (filamentous actin)
- The filaments are polymers of individual actin proteins called G actin (globular actin)
- The combined weight of the filamentous actin and globular actin is 5% of the total
protein of a typical cell
- Shape is a polarised double helix
- It has an asymmetric shape and gives polarity to the filament. The top is positive and
the bottom of the tail is negative.
- Regulates movement of entire cells (eg, neutrophil engulfing bacteria)
- Regulates growth of nerve processes
-
Assembly and growth of the actin filament
- Requires ATP which is bound to each G actin monomer. More ATP is bound to the
plus end of the monomer
- Filaments are very dynamic as they can extend and contract frequently.
- Monomers can be added and removed from both ends of the polymer.
- When the monomer has been added and incorporated into the filament structure then
the ATP is hydrolysed to ADP and there is a release to and an inorganic phosphate is
released.
Function of actin
- Mechanical support eg, cochlea cells in ear
- Changing and supporting shape of cells eg, biconcave red blood cell
- Cell motility eg, muscle cells
- Actin binding proteins modulate polymerisation dynamics and function
- Actin binding proteins allow actin filaments to interact with many different cytoplasmic
proteins and thereby actin’s diverse and essential roles
- They also provide support and can be found beneath the plasma membrane
- Maintain cell shape in erythrocytes
