cell motility: cell movement through cilia and flagella.

1. CELL MOTILITY
CILIAAND FLAGELLA

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.
 Cilia may be 5µm to 10µm in length, while flagella are up to
150µm in length.
 Cilia – numerous (300 - 14000 or more)

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.

7. 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.
 Flagella are microscopic, hair-like structures that help cells
move. The word "flagellum" means "whip".
 Flagella have several functions, including: Facilitating
movement and locomotion, Detecting changes in pH and
temperature, Enhancing reproductive rates in eukaryotes, and
Identifying certain types of organisms.

8. • Monotrichous: A single flagellum, usually at one pole
• Amphitrichous: A single flagellum at both ends of the
organism
• Lophotrichous: Two or more flagella at one or both
poles
• Peritrichous: flagella over the entire surface

9. STRUCTURE
 These projections are covered by a membrane, continuous
with plasma membrane of cell.
 The three main parts of a cilium are the basal body, basal
plate, and shaft (microtubule structure).
 The three main parts of a flagellum are the basal body, hook,
and filament/ shaft.

10.  Basic structure of axoneme discovered in 1952 by Irene
Manton (plants) & Don Fawcett and Keith Porter (animals).
 Central tubules enclosed by central sheath, that is connected
to A tubule by radial spokes.
 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. • Core of cilium is called axoneme, contains an array of
microtubules.
• The basal body is attached to cytoplasm by rootlets.
• All microtubules have same polarity (+ ends at tip of
projection & - end at base).

12. AXONEME
 Length of axoneme vary from a few microns
to2mm.
 Diameter is about 0.2µ to 2000Aº at base,
reaches upto 10µ above cell surface.
 Axoneme is surrounded by an outer
ciliary membrane of 90 Aº thick.
 It is continuous with PM and composed
of lipo-protein.
 Axonemes are a major component of
the root system that anchors a flagellum
within the cell. They also form the
central core of a cilium.
 Axoneme of motile cilium or flagella
consist of nine peripheral doublet
microtubules surrounding central pair of
singe microtubules, known as 9+2
array.
 Each peripheral doublet consist of one
complete tubule, A tubule and one
incomplete, B tubule.

13. Basal body
 Also known as kinetosome, basal granule, proximal
centriole.
 The basal body is a barrel-like microtubular structure that
provides a template for the nine-fold symmetry of the
cilium.
 The core of the basal body in human cells is a ninefold
microtubule-triplet cylindrical structure.
 The distal and subdistal appendages at the distal end of
the basal body play important roles in cilium formation
and function.
 It is hollow cylindrical body and in protoplasm there are
9 groups of tubules. Arrangement of microtubules in
basal body is 9 + 0 arrangement.
 Each tubule is formed of 3 units: 2 units extend into
flagellum and third one ends between basal body and
flagellum. The microtubules are arranged in triplet
manner.

15. EUKARYOTIC CILIUM

16. 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.

17. 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.
 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
neighboring doublet.

18. DYNEIN ARMS
 It was isolated in 1960s by Ian Gibbons. Also known as
ciliary or axonemal dynein.
 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.
 Gibbons said that arms were equivalent to dynein ATPase
molecule, thus it was arms release energy for locomotion.

19. • Doublets are connected to each
other by interdoublet bridge,
composed of nexin.
• Dynein arms are complex
structures that power the beating of
cilia and flagella.
• They are large enzymes that form
inner and outer arms that are
associated with doublet
microtubules within cilia and flagella.
• The inner dynein arms are
responsible for creating the discrete
ciliary wave pattern by controlling
the size and shape of the ciliary
bend.
• The outer dynein arm (ODA) is a
molecular complex that drives the
beating motion of cilia/flagella.

20.  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.

21. 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.

22.  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.

23. 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.

25. 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.
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.

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

27. 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.
• 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.

30. 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.

31. 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.

32. 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)