The cytoskeleton consists of three main types of protein filaments - microtubules, microfilaments, and intermediate filaments. Microtubules provide structure to cells and are involved in cell motility and intracellular transport. Microfilaments are the thinnest filaments and are involved in cell movement and cytoplasmic streaming. Intermediate filaments provide structural support and help maintain cell shape.

3.  The cytoskeleton extends throughout the cytoplasm and
is a complex network of protein filaments.
 Providing structural support to the cell, the cytoskeleton
also functions in cell motility and regulation.
 The existence of an organized fibrous array or
cytoskeleton in the structure of the protoplasm was
postulated in 1928 by Koltzoff.
What is Cytoskeleton?

4. Types of protein filaments
There are three main types of Protein fibers in
the cytoskeleton:
A. MICROTUBULES
B. MICROFILAMENTS
C. INTERMEDIATE FILAMENTS

5.  A microtubule consists of a long, unbranched, hollow
tubules 24–25 nm in diameter and with 6 nm thick wall
having 13 subunits or protofilaments.
 A protofilament of microtubule is made of a protein called
tubulin. It occurs in two different forms, called α-tubulin and
β-tubulin.

6. Functions of Microtubules
 Microtubules are the central structural supports in cilia
and flagella.
 During cell differentiation, the mechanical function of
microtubules is used to determine the shape of the
developing cells.
 Microtubules play a role in the contraction of the spindle
and movement of chromosomes and centrioles as well
as in ciliary and flagellar motion.

7.  Microfilaments are the thinnest class of the cytoskeletal
fibers, approximately 8 nm in diameter.
 Thicker filaments, composed of a motor protein, myosin,
interdigitate with the thinner actin fibers.
 An actin microfilament consists of a twisted double
chain of actin subunits.

8. Function of microfilaments
 Microfilaments are found to be involved in movement
associated with furrow formation in cell division.
 In plant cells(and others), actin-myosin interactions and
sol-gel transformations drive cytoplasmic streaming.
 This creates a circular flow of cytoplasm in the cell.

9.  This speeds the distribution of materials within the cell.

10.  Constructed like woven ropes, they are typically
between 8 nm to 12 nm in diameter, which is
“intermediate” between the thin and thick filaments.
 Intermediate filaments are built from a diverse class of
subunits from a family of proteins called keratins.

11. Function of Intermediate filaments
 They are very stable structures provide
reinforce cell shape and fix organelle
location.
 Intermediate filaments can be anchored
between the membrane to provide extra
support