This document provides a comprehensive overview of the cytoskeleton, including its components, structure, functions, and the processes of polymerisation and assembly.
Molecular Biology of the Cell (5th Edition):
Chapter 16: p970-976, p982-986, p
Molecular Biology of the Cell (6th Edition):
...
Cytoskeleton:
Cytoskeleton - Structures which come together
Made up of 3 components
Organised in a cell to specific structures
Their structure organisation define their function
They are macromolecules (very large molecules)
Cytoskeleton components are essential to form the structure, maintain the structure, shape, and the structural cells
which define the structure of tissues
Forms the framework of every cell
Actin - Structure that forms all of the components/organisation of the body and is essential for all cells in the body
Non-muscle found in all cells
Cytoplasm & Cytoskeleton:
Cytoplasm:
An aqueous environment where many proteins are together, as well as the nucleus
A lot of protein form the backbone
Has a framework which maintains cell structure and organisation e.g. if it was composed of water, liquid,
membranes, nucleus without the framework, the cell won’t be able to structure them
Regarded as a gel-like substance in which organelles and the nucleus were suspended
Cytoskeleton:
Provides an architectural framework for cells
Cytoskeleton has a dynamic changing nature (unlike the skeleton)
Cytoskeleton and all structures of the cytoskeleton have dynamic structures, they can assemble and disassemble
very efficiently
Size Matters:
Cytoskeleton proteins form polymers/fibres built from small protein subunits that are held together by non-covalent
bonds
Cytoskeleton proteins are able to interact with each other to form macromolecules
3 Proteins/Molecules Which Come Together To Form Specific Structures:
Create specific subsets of filaments as they follow certain structures and requirements to be classified in this family
of proteins
4 major types
The proteins vary in size and sequence
Microtubules:
1
, Cells To Systems - Cytoskeleton
2 proteins coming together to form a dimer
α-tubulin
β-tubulin
Because α and β-tubulin are slightly different, they become a heterodimer (HO dimer)
These proteins are very small
By binding together, they can form structures which are long or large
Nerve cells or neurons form axons
Axons are ½ - 1 metre long
Axons are extended like this due to cytoskeleton proteins, which allow the axons to function properly
Cytoskeleton - Common Themes:
Filaments - Architecture and framework which hold and make the cells the way they are
Unlike the bones in the body, filaments are very easily disassembled and organised in change in structure
Filamentous structures are polymers of subunit proteins
State of assembly is dynamic (constantly changing)
Specific changes in assembly are due to interaction with other proteins
Molecular motors allow for intracellular transport and cellular movement
Cytoskeleton proteins are small molecules that can form into large sedimental
polymers/macromolecules/filamins
Reversible pattern = Subunits assemble to form filaments and filaments can disassemble
to form subunits
= process is very efficient and quick
Small molecules can diffuse rapidly within the cytoplasm
1. Large amounts of filaments are organised on 1 side of the cell. However, there is a
source (yellow arrow) which triggers the cell and tells it to act
= as a consequence, this phase is facing the wrong way and needs to reorganise
itself very efficiently
2. Filaments are disassembled
3. Promotes the organisation, reassembly, and polymerisation of these filaments
where it’s required)
Dynamic process where dynamicity is essential (things can act and can be act upon
very efficiently
For this process to take place, energy is required for many events to take place at
the same time and certain molecules e.g. mottos to work
The rate of assembly into polymers, the site of assembly and the stability of the
polymer, once formed, are tightly regulated events
Typical Organisation Of The Cytoskeleton Filaments Within Cells:
Filaments are organised in a specific pattern and cellular localisation which is key function of these molecules
working together
Diameter is important, not length
Actin Filaments:
Smallest diameter
2
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