2. Cytoskeleton
❖ PRESENTATION By:
Group B
❖ Submitted To: Dr. Farooq
Ahmed
❖ Submission Date:
09/12/2020
❖ Group Members:
1. M Ahmed 2. M Shoaib 3. M
Siddique 4. M Shahid 5. Zahid Ali
6. Umema Irfan 7. Ansharah
Shehzadi 8. Tahira Arshad 9.
Zainab Malik 10.Zunaira Salam
11. Tehmina Munir 12. Wajiha Naz
13. Sidra 14. Sana Rasheed
3. ➢ A microscopic network of protein
filaments and tubules in the
cytoplasm of many living cells,
giving them shape and coherence.
❖ Cytoskeleton:
➢ The cytoskeleton is a structure that
helps cells maintain their shape and
internal organization, and it also
provides mechanical support that
enables cells to carry out essential
functions like division and movement.
❑ Graphical Photo of cytoskeleton
4. ❖ Discovery:
➢ Cytoskeleton:
Initially, it was thought that the cytoskeleton was
exclusive to eukaryotes but in 1992 it
was discovered to be present in prokaryotes as well.
➢ Microtubules:
Microtubules were discovered by transmission
electron microscopy in the late 1950s.
➢ Actin/Micro Filaments:
Microfilament/Actin Filaments - Edward David Korn discovered microfilament in 1968 in
Acanthamoeba Castellani.
➢ Intermediate filaments:
Biological specimens enriched in intermediate filament (IF) proteins were among the first to be
placed into an x-ray beam for structural analysis, back in the 1930s by William Astbury.
5. ❖Structure:
5
➢ The cytoskeleton of a cell is made up of
microtubules, actin filaments, and
intermediate filaments.
These structures give the cell its shape and
help organize the cell's parts. In addition,
they provide a basis for movement and cell
division.
➢ Types:
There are three major types of
Cytoskeleton that are given below:
1. Microtubules
2. Microfilaments
3. Intermediate Filaments
6. ~Microtubules are polymers of tubulin that form part
of the cytoskeleton and provide structure and shape to
eukaryotic cells.
~They can grow as long as 50 micrometers and are
highly dynamic.
~The outer diameter of a microtubule is between 23
and 27 nm while the inner diameter is between 11 and
15 nm.
~They are formed by the polymerization of a dimer of
two globular proteins, alpha and beta tubulin into
protofilaments that can then associate laterally to
form a hollow tube, the microtubule.
1. Microtubules:
7. ~The most common form of a microtubule
consists of 13 protofilaments in the tubular
arrangement.
Structure:
~In eukaryotes, microtubules are long, hollow
cylinders made up of polymerized α- and β-
tubulin dimers.
~ The α and β-tubulin subunits are
approximately 50% identical at the amino acid
level, and each have a molecular weight of
approximately 50 kDa.
~Microtubules have a distinct polarity that is
critical for their biological function.
10. Cell migration:
Microtubules are responsible for a variety of cell
movements, including the intracellular transport and
positioning of membrane vesicles and organelles, the
separation of chromosomes at mitosis.
Cilia and flagella:
Microtubules have a major structural role in eukaryotic
cilia and flagella.
Development:
The cytoskeleton formed by microtubules is essential to
the morphogenetic process of an organism's development.
Gene regulation:
They help in gene regulation by helping in cell
division.
❖ Functions Of Microtubules:
11. ~Microfilaments, also called actin filaments, are
polymers of the protein actin that are part of a
cell’s cytoskeleton.
~They are long chains of g-actin formed into two
parallel polymers twisted around each other into a
helical orientation with a diameter between 6 and 8nm.
~Common to all eukaryotic cells, these filaments are
primarily structural in function and are an important
component of the cytoskeleton, along with
microtubules and often the intermediate filaments.
~They are the smallest filaments of the cytoskeleton.
~Their functions include cytokinesis, amoeboid
movement and cell motility in general, changes in cell
shape, endocytosis and exocytosis, cell contractility
and mechanical stability.
2. Microfilaments:
12. ~Microfilaments are primarily composed of polymers of actin, but in
cells are modified by and interact with numerous other proteins.
~They are usually about 7 nm in diameter making them the thinnest
filaments of the cytoskeleton.
~The polymers of these linear filaments are flexible but still strong,
resisting crushing and buckling while providing support to the cell.
~Like microtubules, microfilaments are polar. Their positively
charged, or plus end, is barbed and their negatively charged minus end
is pointed.
❖ Structure of Microfilaments:
~Overall, they have a
tough, flexible framework
that helps the cell in
movement.
13. ~In association with myosin, microfilaments help to
generate the forces used in cellular contraction and
basic cell movements.
~Eukaryotic cells heavily depend upon the integrity of
their actin filaments in order to be able to survive the
many stresses they are faced with within their
environment.
❖ Functions:
~Microfilaments play a key role in the development of various cell surface projections
including filopodia, lamellipodia, and stereocilia. The filaments are also hence involved in
amoeboid movements of certain types of cells.
~They can depolymerize (disassemble) and reform quickly, thus enabling a cell to change its
shape and move.
~Microfilaments as a part of the cytoskeleton keep organelles in place within the cell. They
provide cell rigidity and shape.
~Microfilaments as a part of the cytoskeleton keep organelles in place within the cell. They
provide cell rigidity and shape.
14. ~Intermediate filaments are important
components of the cell's cytoskeletal system.
~They may stabilize organelles, like the nucleus,
or they may be involved in specialized junctions.
~They are distinguished from "thin filaments" by
their size (8-10 nm) and the fact that thin
filaments are obviously motile.
~They range in diameter from 8-10 nm
(intermediate in size compared with thin filaments
and microtubules).
~They are prominent in cells that withstand
mechanical stress and are the most insoluble part
of the cell. The intermediate filaments can be
dissociated by urea.
3. Intermediate Filaments:
15. ~The intermediate filaments are
diverse; some 65 separate genes in
humans have been identified.
~They all consist of three parts: a
“head,” a long rod-like central part,
and a “tail.”
~Examples of intermediate
filaments include vimentin, desman,
glial fibrillary acid protein (GFAP),
neurofilaments, and nuclear
laminins.
❖Structure:
16. ~Intermediate filaments (IFs) are a type of cytoskeletal fiber found in many
eukaryotic cells; they're also believed to be found in fungi and other single-celled
eukaryotes, but that has not been fully accepted by scientists.
~In some cells, there are as many as ten times the number of intermediate filaments
as there are other microfilaments or microtubules.
~This abundance of ifs means they serve several important roles in the cell.
~Intermediate filaments are usually strong and ropelike.
~Their job is mainly structural, providing strength and support for the more fragile
tubulin structures.
~All cells have intermediate filaments, and some cells have several different types.
~Some intermediate filaments are closely linked to specific cell types.
~Neurofilaments, as the name suggest, are found exclusively in neurons.
~The function of intermediate filaments is largely mechanical, meaning they provide
support for the cell so that other microfilaments can more readily do their transport
jobs.
❖Function:
17. ~First, it gives the cell shape.
~This is especially important in cells without cell walls, such as animal cells, that do
not get their shape from a thick outer layer.
~It can also give the cell movement.
~The microfilaments and microtubules can disassemble, reassemble, and contract,
allowing cells to crawl and migrate, and microtubules help form structures like cilia
and flagella that allow for cell movement.
~The cytoskeleton organizes the cell and keeps the cell’s organelles in place, but it
also aids in the movement of organelles throughout the cell.
~For example, during endocytosis when a cell engulfs a molecule, microfilaments pull
the vesicle containing the engulfed particles into the cell.
~Similarly, the cytoskeleton helps move chromosomes during cell division.
~One analogy for the cytoskeleton is the frame of a building. Like a building’s frame,
the cytoskeleton is the “frame” of the cell, keeping structures in place, providing
support, and giving the cell a definite shape.
❑ Overall Functions Of Cytoskeleton:
