Cilia and FlagellaCilia and Flagella
Structure and Function inStructure and Function in
By Justin Robbins and KatrinaBy Justin Robbins and Katrina
Cilia and Flagella areCilia and Flagella are
organelles that areorganelles that are
primarily used for theprimarily used for the
transportation of the cell.transportation of the cell.
They propel the cell byThey propel the cell by
flicking back and forth.flicking back and forth.
Cilia are short andCilia are short and
reminiscent of hairs.reminiscent of hairs.
There are many per cell.There are many per cell.
Flagella are longer andFlagella are longer and
there are far fewer perthere are far fewer per
cell. They are reminiscentcell. They are reminiscent
of a tail.of a tail.
Real-life Examples:Real-life Examples:
Most common in single-celled organismsMost common in single-celled organisms
However, some multi-cellular organisms haveHowever, some multi-cellular organisms have
cilia and flagella.cilia and flagella.
Human windpipe cells and some lung cells have ciliaHuman windpipe cells and some lung cells have cilia
to clean the respiratory system of breathing hazards.to clean the respiratory system of breathing hazards.
Fish have cilia to help bring water through the gills.Fish have cilia to help bring water through the gills.
Many types of sperm have flagella to help them move.Many types of sperm have flagella to help them move.
Structure: 9+2 PatternStructure: 9+2 Pattern
Cilia or flagella is composed ofCilia or flagella is composed of
microtubules that are encased in amicrotubules that are encased in a
plasma membrane. This bundle ofplasma membrane. This bundle of
microtubules is called the axoneme.microtubules is called the axoneme.
A plasma membrane is made of lipidsA plasma membrane is made of lipids
and proteins and is essentially the sameand proteins and is essentially the same
as a normal cell membrane.as a normal cell membrane.
There are 9 pairs of connectedThere are 9 pairs of connected
microtubules in a circle towards themicrotubules in a circle towards the
outside edge of the cilia/flagella. Theseoutside edge of the cilia/flagella. These
are called the outer microtubuleare called the outer microtubule
The outer microtubules are connectedThe outer microtubules are connected
to each other in a ring with cross-linksto each other in a ring with cross-links
(not pictured).(not pictured).
The outer microtubules also connect toThe outer microtubules also connect to
the center structure with radial spokes.the center structure with radial spokes.
These outer microtubules surroundThese outer microtubules surround
another pair of central microtubules,another pair of central microtubules,
which are not connected.which are not connected.
Structure: Basal BodyStructure: Basal Body
The 9+2 patternThe 9+2 pattern
continues throughout thecontinues throughout the
entire organelle until theentire organelle until the
The base is called theThe base is called the
Basal Body. It is theBasal Body. It is the
foundation of the cilia orfoundation of the cilia or
flagella and is embeddedflagella and is embedded
in the cell membrane.in the cell membrane.
It does not have a pair ofIt does not have a pair of
central microtubules.central microtubules.
Instead, it has nineInstead, it has nine
triplets of microtubules.triplets of microtubules.
How They Work: Dynein ArmsHow They Work: Dynein Arms
Each of the outer microtubule pairsEach of the outer microtubule pairs
have a set of dynein, a functionalhave a set of dynein, a functional
protein, arms.protein, arms.
These arms change shape andThese arms change shape and
subsequently create a sliding force,subsequently create a sliding force,
therefore moving the tubule pairs.therefore moving the tubule pairs.
Since the pairs are held togetherSince the pairs are held together
with cross-links and are anchored inwith cross-links and are anchored in
the cell membrane, thethe cell membrane, the
microtubules bend as a result of thismicrotubules bend as a result of this
If they were not held together, theIf they were not held together, the
force exerted would cause the twoforce exerted would cause the two
doublets to slip past each other.doublets to slip past each other.
This bending motion makes the ciliaThis bending motion makes the cilia
or flagella to flick back and forth,or flagella to flick back and forth,
therefore propelling the celltherefore propelling the cell
How They Work: ATPHow They Work: ATP
The change of shapeThe change of shape
of the dynein arms isof the dynein arms is
powered by ATP.powered by ATP.
ATP, or Adenine-Tri-ATP, or Adenine-Tri-
Phosphate, isPhosphate, is
molecule that mostmolecule that most
cells use as theircells use as their
main energy source.main energy source.
Differences in Motion:Differences in Motion:
single-celled organismssingle-celled organisms
Cilia movement is well timed with eachCilia movement is well timed with each
other and propel the organism in a wave-other and propel the organism in a wave-
like motion.like motion.
Flagella in eukaryotes give the organismFlagella in eukaryotes give the organism
smoother movement.smoother movement.
Flagella in prokaryotes rotate, like a motor.Flagella in prokaryotes rotate, like a motor.
Primary CiliaPrimary Cilia
Primary Cilium are an alternate type of cilia.Primary Cilium are an alternate type of cilia.
They do not aid in motion and are thereforeThey do not aid in motion and are therefore
referred to as immotile cilia.referred to as immotile cilia.
Primary cilia do not have central microtubules.Primary cilia do not have central microtubules.
They have a 9+0 structure.They have a 9+0 structure.
They have sensory functions.They have sensory functions.
Examples: monitoring flow in the kidneys andExamples: monitoring flow in the kidneys and
detecting smells.detecting smells.
Defects in kidney primary cilia can lead toDefects in kidney primary cilia can lead to
kidney disease.kidney disease.
Campbell, Mitchell, and Reece. "Cilia and Flagella Move When Microtubules Bend."Campbell, Mitchell, and Reece. "Cilia and Flagella Move When Microtubules Bend."
Biology: Concepts and ConnectionsBiology: Concepts and Connections. 3rd ed. Reading, Massachusetts:. 3rd ed. Reading, Massachusetts:
Benjamin/Cummings, 2000. 65. Print.Benjamin/Cummings, 2000. 65. Print.
Campbell, Mitchell, and Reece. "Glossary." Campbell, Mitchell, and Reece. "Glossary." Biology: Concepts and ConnectionsBiology: Concepts and Connections. 3rd. 3rd
ed. Reading, Massachusetts: Benjamin/Cummings, 2000. G-18. Print.ed. Reading, Massachusetts: Benjamin/Cummings, 2000. G-18. Print.
Cilia and FlagellaCilia and Flagella. Photograph. University of Illinois. Web. 21 Nov. 2010.. Photograph. University of Illinois. Web. 21 Nov. 2010.
Davidson, Michael W. "Cilia and Flagella."Davidson, Michael W. "Cilia and Flagella." Molecular ExpressionsMolecular Expressions. Florida State. Florida State
University, 13 Dec. 2004. Web. 21 Nov. 2010.University, 13 Dec. 2004. Web. 21 Nov. 2010.
Diagrams of Cilia and Flagella. Digital image.Diagrams of Cilia and Flagella. Digital image. Both Brains and BeautyBoth Brains and Beauty. Web.. Web.
Diagrams of Dynein Arms. Digital image. University of Illinois. Web. 21 Nov. 2010.Diagrams of Dynein Arms. Digital image. University of Illinois. Web. 21 Nov. 2010.
Kimball, John W. "Cilia and Flagella."Kimball, John W. "Cilia and Flagella." Kimball's Biology PagesKimball's Biology Pages. 28 July 2007. Web. 21. 28 July 2007. Web. 21
Jan. 2010.Jan. 2010.