cell motility is facilitated either by cilia or flagella

1. CELL MOTILITY-
CILIA AND
FLAGELLA
Allie N U,
MSc biotechnology

2. INTRODUCTION
 Microscopic contractile and filamentous
structure of cytoplasm.
 It create food currents, act as sensory
organs and perform many mechanical
functions of the cell.
 Cilia and flagella are identical structures but
both can be distinguished by their number
and function.

3. CILIA AND FLAGELLA
 Hair like motile organelles project from surface of
variety of eukaryotes.
 Cilium likened to an oar, it moves the cell in
direction perpendicular to cilium itself.
 It become flexible and occur in large numbers on
the cell surface. And their beating activity is
coordinated.
 Flagella occur singly or in pair, exhibit a variety of
different beating pattern depending on cell type.

4. CILIA
 Cilia and flagella are more likely similar in structure.
 In power stroke, cilium maintained in a rigid state as
it pushes against the surrounding medium.
 In recovery stroke, cilium become flexible offering
little resistance to the medium.

5.  In multicellular organisms, cilia move fluid and
particulate material through various tracts.
 In humans, ciliated epithelium lining the respiratory
tract propel mucus and trapped debris away from
lungs.
 Many cells of the body contain a single non motile
cilium called primary cilium.
 It have a sensory function, monitoring mechanical
and chemical properties of extracellular fluids.

6. FLAGELLA
 Occurs in single or pairs and
exhibit a variety of beating patterns
or waveforms.
 Eg : single celled algae pulls itself
forward in asymmetric manner.
 This algal cell can also push itself
using a symmetric beat in medium.
 Degree of asymmetry in pattern of
beat is regulated by internal
calcium ion concentration.

7.  Cilia may be 5µm to 10µm in length, while flagella
are upto 150µm in length.
 Flagella – less number(1,2,4)
 Cilia – numerous(300- 14000 or more)

8. STRUCTURE
 Entire ciliary or flagellar projection is covered by a
membrane , continuous with plasma membrane of cell.
 Core of cilium is called axoneme, contains an array of
microtubules.

9.  Axoneme of motile cilium or flagella consist of nine
peripheral doublet microtubules surrounding central
pair of singe microtubules, known as 9+2 array.
 All microtubules have same polarity ( +ends at tip of
projection & -end at base).
 Each peripheral doublet consist of one complete
tubule, A tubule and one incomplete, B tubule.
 Basic structure of axoneme discovered in 1952 by
Irene Manton (plants) & Don Fawcett and Keith
Porter (animals).

10.  Central tubules enclosed by central sheath, that is
connected to A tubule by radial spokes.
 Doublets are connected to each other by
interdoublet bridge, composed of nexin.
 A pair of arms ( an inner arm & outer arm) project
from A tubule.
 Cilium or flagellum emerges from a basal body.
 If a cilium is sheared , a new organelle is
regenerated as outgrowth of basal body.

11. CROSS SECTION OF CILIUM FLAGELLA

12. AXONEME
 Length of axoneme vary from a few microns to
2mm. Diameter about 0.2µ to 2000Aº at base,
reaches upto 10µ above cell surface.
 Axoneme is surrounded by an outer ciliary
membrane of 90Aº thick.
 It is continuous with PM and composed of
lipoprotein.

13. EUKARYOTIC CILIUM

14. CHEMISTRY OF AXONEME
 Microtubules and arms contains chemicals like;
 TUBULINS: these proteins have mol wght 55000 to
60000. they are tubulin A and tubulin B. also
contains about ten soluble secondary proteins.
 DYENIN: myosin like protein, occur in arms, radial
linkages and their attachment to core surface.
Dimeric protein and has ATPase activity.

15. BASAL BODIES
 Flagellum or cilium arises from spherical or granular
or short rod shaped body – basal body.
 Also known as kinetosome, basal granule, proximal
centriole.
 They are structurally similar to centrioles.
 It is hollow cylindrical body and in protoplasm there
are 9 groups of tubules.
 Each tubule is formed of 3 units:- 2 units extend
into flagellum and third one ends between basal
body and flagellum.

17. CILIARY ROOTLETS
 Additional hair like structure arise from basal body and
extend to cytoplasm – ciliary rootlets.
 Characteristics of ciliated epithelial cells of mammals.
 Also help to anchor basal body with cilium.

18. INTRAFLAGELLAR TRANSPORT
 Movement of particles in space between peripheral
doublets and surrounding plasma membrane is
called intraflegellar transport (IFT).
 It is responsible for assembling and maintaining
these organelles.
 IFT depend on activity of both plus and minus end.
 Kinesin 2 moves complex arrays of IFT particles
together with associated building materials along
protofilaments of peripheral doublets to assembly
site at tip of growing axoneme.

19.  Kinesin 2 molecules transported back towards
basal body by cytoplasmic dynein powered
mechanism

20. DYNEIN ARMS
 In an experiment, a sperm tail axoneme devoid of
its overlying membrane is still capable of normal,
sustained beating in presence of Mg²+ and ATP.
 Protein responsible for conversion of chemical
energy of ATP into mechanical energy of ciliary
locomotion called dynein.
 It was isolated in 1960s by Ian Gibbons.
 Also known as ciliary or axonemal dynein.
 Gibbons said that arms were equivalent to dynein
ATPase molecule, thus it was arms release energy
for locomotion

21.  Dynein molecule consists of three heavy chains
and a number of intermediate and light chains.
 Each dynein heavy chain is composed of a long
stem, a wheel shaped head and a stalk.

22. MECHANISM OF CILIARY AND FLAGELLAR
LOCOMOTION
 Contraction of muscle results from sliding of actin
filaments over adjacent myosin filaments.
 As muscle system as a model, ciliary motion was
explained by sliding of adjacent microtubular
doublets relative to one another.
 Dynein arms act as swinging cross bridges.
 It generate forces required for ciliary or flagellar
movement.

23.  In intact axoneme, stem of each dynein molecule is
tightly anchored to outer surface of A tubule.
 With globular head and stalks projecting towards B
tubule of neighbouring doublet.

24.  Dynein arms anchored along A tubule
of lower doublet attach to binding
sites on B tubule of upper doublet.
 Dynein molecules undergo
conformational change, or power
stroke causes lower doublet to slide
towards basal end of upper doublet.
 Dynein arms have detached from B
tubule of upper doublet.
 Arms have reattached to upper
doublet so another cycle get started.

25. NEXIN
 Nexin is an elastic protein that connects adjacent
doublets.
 Play important role in ciliary or flagellar movement
by limiting the extent that adjacent doublets can
slide over one another.
 Resistance to sliding provided by nexin bridges
cause axoneme to bend in response to sliding
force.

27. BACTERIAL FLAGELLA
 Simpler in structure.
 Consists of three portions: terminal hook, main
shaft and a basal region.
 Consists of single fibres.
 They are not made of 9+2 filaments but are simply
cylinders.
 Composed of globular molecules of 40Aº in
diameter, arranged in hexagonal packing with
helical twist.

28.  Flagella are composed of flagellin.
 It is similar to actin and does not contain ATPase.

29. A bacterial flagellum has 3 basic parts: a filament, a hook, and
a basal body.
1) The filament is the rigid, helical structure that extends from
the cell surface. It is
composed of the protein flagellin arranged in helical chains so
as to form a hollow core.
During synthesis of the flagellar filament, flagellin molecules
coming off of the ribosomes
are transported through the hollow core of the filament where
they attach to the growing tip
of the filament causing it to lengthen.
2) The hook is a flexible coupling between the filament and the
basal body
.

30. 3) The basal body consists of a rod and a series of rings that
anchor the flagellum to the
cell wall and the cytoplasmic membrane (see Fig. 1). Unlike
eukaryotic flagella, the
bacterial flagellum has no internal fibrils and does not flex.
Instead, the basal body acts as
a rotary molecular motor, enabling the flagellum to rotate and
propel the bacterium
through the surrounding fluid

33. FUNCTIONS OF CILIA AND FLAGELLA
Cells in motion:
 Cellular appendages capable of specific types of
movement.
 Flagella are capable of undulating or rotational
movement.
 With a whip like motion, cilia can move from one place
to another.
Cells that swim:
 Eukaryotic flagella exhibit wiggling or undulating
movement to propel an entire cell.
 Eg ; single celled protozoa use flagella to swim through
aquatic environment for food.
 Reproductive cells use flagella for locomotion.

34. A bacterial motor:
 Tail like extension or filament of bacterial flagellum is
connected through a hooked segment to proteins that
generate torque.
 This motor rotates the entire filament which moves the
bacterium.
Cellular dusting:
 Group of cilia work together for steady movement of
water, mucous, and other extra cellular substances.
 Eg :human respiratory tract contain special cells called
ciliated epithelial cells.
 They work together with goblet cells to keep lungs
clean.

35. Taxis
Around half of all known bacteria are motile. Motility serves to
keep bacteria in an optimum
environment via taxis (def).
Taxis is a motile response to an environmental stimulus.
Bacteria can respond to chemicals (chemotaxis), light
(phototaxis), osmotic pressure (osmotaxis), oxygen
(aerotaxis), and temperature (thermotaxis)