CILLIA AND FLAGGELA, CELL ORGANELLE

1. CELL BIOLOGY
BTH 2ND SEM

2.  It may involve movement of the entire cell or
a portion of it, to advantage of the organism
 Eg feeding, protection, digestion,
reproduction , circulation
 Flagella, cilia microvilli in the digestive
system
 Muscle system for motion of cell or an
organism

3. Locomotion helps to
 Find food
 Avoid unfavourable conditions
 Escape from predator
 Find out mate
 Takes place in respose to the stimuli

4.  Cilia(Latin for eyelash);
Flagellum(Latin means whip)
 Are the organelles that are primarily used for
the transportation/ locomotion of cell
 are fine vibratile cytoplasmic processes arising
from basal bodies.
 They are similar in their structure, chemical
composition and function.
 Both serve to propel the organism or move a
medium past a fixed cell.
 BUT differ in their size, number and mode of
beating.

5.  Are characteristic of cells that live in fluid or aquatic
media
 Are the organelles that are primarily used for the
transportation/ locomotion of cell
 are fine vibratile cytoplasmic processes arising from
basal bodies.
 They are similar in their structure, chemical
composition and function.
 Both serve to propel the organism or move a
medium past a fixed cell.
 BUT differ in their size, number and mode of
beating.

6.  Flagellum(Latin means whip)
 long, slender,
 thread like projections from the surface
 fine vibratile cytoplasmic processes arising from
basal bodies
 The base of flagellum is anchored in the cytoplasm
on a motion controlling kinetosome region or
granule
 Flagella ( Algae, protozoans like Euglena and in
several examples of algae. They also occur in
choanocytes of sponges.
 Number- Only 1 ,
 sometime more and anchored in the kinetochore granules

7.  Cilia(Latin for eyelash)
 short, slender,
 thread like projections from the surface
 fine vibratile cytoplasmic processes arising
from basal bodies
 Each cillium has its own kinetosome at its
base
 Flagella ( occur in protozoans like Euglena
and in several

9.  Primary Cilium are an alternate type of cilia.
They do not aid in motion and are therefore
referred to as immotile cilia.
 Primary cilia do not have central
microtubules. They have a 9+0 structure.
 They have sensory functions.
 Examples: monitoring flow in the kidneys and
detecting smells.
 Defects in kidney primary cilia can lead to
kidney disease.

10.  Cilia occur in protozoans like Paramecium and in flame cells of
flatworms. They also occur in epithelial cells lining moist regions of the
body.
 The cilia normally exhibit a metachronous or isochronous rhythmic beat.
a) metachronous beat, cilia of a row beat one after the other
b) isochronous rhythm all the cilia of a row beat simultaneously.
 The beating of cilia occurs in two phases
 Power or effective phase
 Recovery phase.
 During power phase cilia become straight and stiff and move against the
medium such as water. This movement pushes water backwards and
propels the organism forwards.
 In the recovery phase, cilia become limp and return to their original
position in a curved state, offering minimum resistance to water. The
whole movement can be compared to the rowing of a boat. ATP is
utilized during both the phases.

13. 1.Regulation of ciliary movement.
Ciliary movement is independent of the nervous system. This is evidenced by the fact
that
If ciliated epithelium is removed from the organism, the cilia continue to move
rhythmically.
Cystoplasmic continuity is, however, essential for coordinated movement of cilia. If a piece
of ciliated epithelium is cut into two, three is no coordination of ciliary movement in the
two pieces.
It has been proposed that rhythmic movement of cilia takes place in two steps,intraciliary
excitation and interciliary conduction.
2. Contractile units of the flagellum are distributed throughout its lengths. Flagella
were broken into pieces by irradiation with a laser microbeam. It was found that the pieces
were able to initiate and propagate contraction for up to ten cycles. This demonstrates that
the contractile units of the flagellum are distributed throughout the length of the flagellum.
This fact is borne out by the observation that the amplitude of the wave of contraction does
not decrease as it approaches the tip of the flagellum.
3. Plane of ciliary movement.
In Opalina the bending movements of the cilia occur perpendicularly to the central tubule
plane.

15. Movements of cilia and flagella are of four types:
pendulous,unciform, infundibuliform and undulant.
(i) Pendulous movement. The cilium moves in one plane. It is
flexed at its base and remains rigid during motion. This type
of movements is found in the ciliate Protozoa, e.g.
Paramecium.
(ii) Unciform movement also takes place in one plane. The
cilium bends into the shape of a hook during contraction.
(iii) Infundibuliform movement. The cilium or flagellum rotates
at its base and moves in different planes, describing a funnel,
shaped figure.
(iv) Undulant movement. The waves of contraction start from the
base and move to the tip.

16. There are two main theories regarding movement of cilia and
flagella.
These are called the localized contraction and the sliding
filamentmodels.
The localized contraction model. Bending takes place by
means of contractile units arranged at regular intervals
along the length of the axoneme. The theory supposes that
there is a change in the length of the subfibres of the
doublets during ciliary movements.
The sliding filament model. According to this theory, bending
of the cilium is initiated by sliding of the tubules of the
peripheral fibrils relative to one another. This theory is
analogous to the mechanism of muscle contraction.

17.  A flagellum is a whip-like organelle that pulls or
pushes the cell through its aqueous environment
 Flagella are usually used for the movement of
single cells.
 Flagella occur in protozoans like Euglena and in
several examples of algae. They also occur in
choancytes of sponges.
 The beating of flagella is independent and
involves an undulating movement. The waves of
undulation pass from the base to the tip of the
flagellum. Power and recovery strokes of the
flagellum move the cell forwards.

20. cilia flagella
 Short
 Usually many present
 Move with stiff power stroke and flexible
recovery stroke
 Found on the surface of multicellular
organisms
 Examples:
 Cilia line the respiratory tract to trap debris
to be removed from the throat
 cilia move a paramecium,
 cilia propel food towards the feeding
groove Paramecium;
 move the egg (or zygote) along the oviduct
 Longer
 Usually one or two present
 Movement is snake-like
 Found on the unicellular organism or
single cell to help in movement through
their environment
 Examples:
 human sperm moves by a flagellum
 flagella in sponges beat to create a water
current for respiration

22.  In eukaryotes, cilia and flagellum are made of
protein and microtubules, which are composed of
linear polymer of globular protein called tubulin.
 The cilia and flagella are surrounded by a
membrane. It encloses a matrix containing a
supporting shaft or axoneme. The axoneme is
composed of eleven microtubules (9+2
arrangement).
 The movement of cilia and flagella is brought
about by sliding of the nine double microtubules
past each other, using energy from ATP.

24.  Flagella and cilia are enclosed by a plasma
membrane :
 made of microtubules in “9 + 2” array
 Membrane of cilia and flagella is an extension
of the plasma membrane
 Axoneme: the central strand of a cilium or
flagellum, composed of an array of
microtubules, typically in 9+2 arrangement
 Basal body / kinetosome: Connects cilium or
flagellum just below the plasma membrane

26.  Axoneme: microtubules in 9+2 arrangement
 Outer nine sets are called doublet microtubules
 Central microtubules and plasma membrane
 Basal body:9+0 array of microtubules
 Nine microtubule triplets (9+0)
 each doublet is accompanied by another
microtubule, making nine sets of three
microtubules
 the central, unfused microtubules do not extend
into the basal body
 is derived from a centriole
 Controls the direction of cilia

32.  Microtubule doublets in cilia & flagella are linked by proteins
 Nexin
 Inner-arm dynein
 Outer-arm dynein
 Role of dynein :
 dynein molecules attached to one microtubule bind to a neighbouring
microtubule
 as the dynein molecules change shape, they move the microtubule past
its neighbour
 Dynein arms: are motor complexes which produce the force needed for
bending.
 Nexin: inter-doublet linkage that prevents microtubules in the outer
layer of axonemes from movement with respect to each other.
 Radial spoke:
 is another protein complex
 spoke projects from each set of outer doublets toward the central
microtubules
 thought to be important in regulating the motion of the axoneme

33.  motion of cilia and flagella results from the
sliding of the microtubules past each other
driven by a motor protein called dynein which
can undergo changes in its shape driven by
energy from ATP.
 Nexin cross-links the doublets preventing
them from sliding: thus cilium bends

35. Role of the central tubules.
It has been shown that the 9 peripheral fibrils are involved
in ciliary movement. In Chlamydomonas the central
tubules are absent in some mutants. Such mutatnts are
non-motile. The suppressed mutants have both functional
and non-functional flagella. This suggests that the central
tubules are essential for flagellar contraction. It has,
however, been suggested that the role of the central
tubules could be the initiation and regulation of flagellar
beat rather than contraction itself.

36.  A eukaryotic flagellum is surrounded by the
plasma membrane and contains a 9+2 array of
microtubules. Nine fused pairs of microtubules,
called doublets, form an outer cylinder and one
pair of unfused microtubules runs up the centre.
A spoke radiates from one microtubule of each
pair and connects the doublet at the centre of the
structure. In the cytoplasm at the base of each
flagellum is an organelle called a basal body. The
nine microtubule doublets extend into the basal
body. The protein called dynein is permanently
attached to one microtubule and moves it with
respect to a neighbouring one.

38. Bacterial flagella Eukaryotic flagella
 Smaller and simple
structure
 Made of protein
flagellin(53 KDa
subunit)
 Rotatory movement
 Protein driven
 Larger and and
complex structure
 Tubulin (9+2
microtuble
arrangement)
 Bending movement
 ATP driven