Difference Between Cilia and Flagella
Cilia and flagella are fine, hair-like structures made of microtubules that project from the surface of cells. They are involved in locomotion, movement of fluids across cell surfaces, and sensory functions. Cilia are usually short and numerous, whereas flagella are longer and fewer in number. Both exhibit the characteristic “9+2” arrangement of microtubules and are important topics in Cell: The Unit of Life, frequently asked in NEET and board exams.
This Story also Contains
- What are Cilia and Flagella?
- Structure of Cilia and Flagella
- Types of Cilia and Flagella
- Function of Cilia and Flagella
- Key Differences Between Cilia and Flagella
- Similarities Between Cilia and Flagella
- Diseases and Disorders Related to Cilia and Flagella
- Cilia vs Flagella NEET MCQs (With Answers & Explanations)
- Recommended video for Cilia and Flagella
What are Cilia and Flagella?
Cilia and flagella are slender structures, made of microtubules but they possess different functions and properties. Ependymal cilia are shorter and present in large numbers, involved in mechanisms such as the clearance of mucus in the respiratory system and signal elimination in sensory organs. Flagella are longer, though fewer in number. In many microorganisms, cilia and flagella help the cell move. They beat in rotational or wave-like patterns, which help the cell to move forward and allow it to change direction.
Structure of Cilia and Flagella
The structure of cilia and flagella is given below-
Structure of Cilia
Cilia are slender, tubular extensions from the cell membrane or surface of the cell. They are usually abundant on the cell membrane and have been noted to be essential components of the cell membrane. Cilia have a basic structural component called the axoneme.
Structure of Flagella
Flagella are longer, thinner, and fewer than cilia. It has the movement of a whip. These come out of the cell surface and are concerned with cell movement.
9+2 Arrangement of Microtubules
The 9+2 arrangement is the characteristic structure of motile cilia and eukaryotic flagella. It consists of nine peripheral doublets of microtubules arranged in a circle around two central single microtubules. This organization provides stability and allows the sliding of microtubules that generates the bending and beating motion of cilia and flagella.
Types of Cilia and Flagella
Types of cilia and flagella are discussed below:
Motile and Non-motile Cilia
Cilia are classified into two types:
Motile Cilia | Non-motile Cilia | |
Function | Involved in the movement of fluids and therefore have crucial functions like mucus removal from the respiratory system and movement of the eggs in the fallopian tubes. | Mainly function as tabs that help in perceiving signals in the environment and transmitting them into the cell. |
Examples | Identified in the respiratory tract’s epithelial cells and the epithelium of the female reproductive system. | Located on olfactory neurons located in the nose and photoreceptor cells of the retina. |
Prokaryotic and Eukaryotic Flagella
Flagella are classified into two types:
Prokaryotic Flagella | Eukaryotic Flagella | |
Structure | Small structures made up of flagellin and are mainly involved in movement. | Elaborate structures that are made up of microtubules in the “9+2” formation. |
Movement | Rotational movement occurs with bacteria as they propel themselves through the water as they search for nutrients. | Come in a sinusoidal pattern that they help in the propulsion and the movement of the cell. |
Examples | Usually found in bacteria like E. coli and Salmonella | Present in sperms for movement, and some of the protozoa for movement. |
Function of Cilia and Flagella
Following describe the function and mechanism of cilia and flagella-
Locomotion
Cilia enable the movement of several organisms ranging from single-celled such as Paramecium to complex organisms including humans. In Paramecium, the coordinated coordination of cilia is vital for the movement through water, in the respiratory tract the ciliary movement is important in the removal of mucus and other materials.
While flagella are mostly involved in cell movement and navigation, the primary purpose of flagella is to allow an organism to move within its environment. In bacteria, moving by swimming and orienting in the space is facilitated by the flagella while in sperm cells, it moves the cell towards the egg during reproduction
Sensory perception
Cilia are involved in sensory functions, receive signals from the environment and translate these signals to the cell. In the human body, primary cilia take part in the transduction of various signals which includes the sensory processes of kidneys and eyes.
Like cilia, flagella occasionally have some sort of sensation function to feel changes in the surroundings and affect corresponding behavioural reactions. For instance, the bacterial flagella have chemotactic properties. This means that bacteria can feel chemical differences and can move in the direction of such differences to locate the best conditions.
Key Differences Between Cilia and Flagella
The following table summarises the structural and functional differences between cilia and flagella:
Aspect | Cilia | Flagella |
Structure | Shorter, numerous, "9+2" arrangement of microtubules | Longer, fewer, "9+2" arrangement of microtubules |
Present in large numbers on the cell surface | Typically fewer in number | |
Primarily involved in locomotion and fluid movement | Mostly sensory roles | |
Function | Facilitate movement, fluid flow, and sensory perception | Enable cell propulsion and sensory functions |
Found in the respiratory tract, reproductive system, and sensory organs | Found in bacteria, sperm cells, and certain protists | |
Movement | Coordinated beating pattern | Wave-like undulation or rotational movement |
Generates fluid movement or propels cells | Propels cells through a fluid medium |
Similarities Between Cilia and Flagella
The following table summarises the similarities between cilia and flagella:
Aspect | Cilia | Flagella |
Shared Structural Components | Both are composed of microtubules and associated proteins | Microtubule-based structures with dynein arms |
Common Origin | Evolved from ancestral motility structures | Shared evolutionary pathways |
Functional resemblance | Are used to move liquid across the cells. | They also help to move liquids past the cells. |
Diseases and Disorders Related to Cilia and Flagella
The diseases and disorders are explained below-
Ciliary Disorders (PCD, Kartagener Syndrome)
Primary ciliary dyskinesia: PCD is an inherited disease that is associated with a failure of ciliary motility resulting in repeated respiratory infections, sinus, bronchiectasis, and problems in conception.
Kartagener syndrome: It is also called primary ciliary dyskinesia with situs inversus, and is featured by chronic respiratory infections, sinusitis, bronchiectasis, and inversion of the heart and liver.
Flagellar Disorders (Infertility, Bacterial infections)
Impact on fertility: Mutations in flagella of the sperm can be a cause of male infertility due to the problems associated with the motility of sperm found in semen to subsequently fertilize the egg.
Bacterial infections: Flagella are involved in the pathogenesis and virulence of different bacteria, including Salmonella, and Pseudomonas aeruginosa because they facilitate the organisms’ invasion of host tissues and the development of infections.
Cilia vs Flagella NEET MCQs (With Answers & Explanations)
Important topics for NEET are:
Structure of Flagella
Structure of Cilia
Cilia vs Flagella
Practice Questions for NEET
Q1.Microtubules in cilia and flagella are arranged in
9 + 2 pattern
9 + 0 pattern
Both A and B
None of these
Correct answer: 1) 9 + 2 pattern
Explanation:
Flagella and cilia are cell structures that facilitate movement. Flagella are long, hair-like appendages used for the movement of the entire cell and are usually present as a single or few structures. Cilia, on the other hand, are short, hair-like projections that cover the cell surface. Both flagella and cilia have the same structure in terms of their microtubules arranged in a 9 + 2 pattern, where two central microtubules are surrounded by nine pairs, thus facilitating efficient movement.
Hence, the correct answer is Option (1) 9 + 2 pattern.
Q2. Whipping action is produced by
Cilia
Microcilia
Flagella
All of these
Correct answer: 3) Flagella
Explanation:
Cilia and flagella are critical to cell movement but differ in various key features. Cilia are small, hair-like protrusions that are significantly shorter (5-6 µm), much smaller in number on the surface of the cell and usually found in organisms such as fungi, protozoa, and epithelial cells in the respiratory tract. They manifest a paddle-like motion. On the other hand, flagella are whip-like protrusions that can measure up to 1000 µm, and in fewer numbers; they have the rotary motion of movement.
Hence the correct answer is option 3) Flagella.
Q3. The motile bacteria are able to move by:
Fimbriae
Flagella
Cilia
Pili
Correct answer: 2) Flagella
Explanation:
Cilia and Flagella are hair like outgrowths of the cell membrane, responsible for cell movement.
- wherein
Flagella in prokaryotic cells, if present, are single stranded, and without differentiation of axoneme and sheath. Flagella helps in movement of bacteria.
Hence, the correct answer is option 2) Flagella.
Also Read:
Recommended video for Cilia and Flagella
Frequently Asked Questions (FAQs)
Cilia and flagella are structurally made of microtubules in the pattern of “9+2”, which means nine doublets of microtubules surrounding two microtubules in the center.
Some organisms with cilia are paramecium, a kind of protozoa that uses cilia for movement, and cells in the human respiratory tract for moving the mucus. Some examples of organisms with flagella are sperms who use them in swimming to the egg and Euglena one of the protists that uses flagella in moving.
Genetic disorders that affect cilia structure and their ability to move are primary ciliary dyskinesia or PCD and Kartagener syndrome. Problems with the flagella in sperms can result in male sterility, conversely, the flagellar motility assists pathogenic bacteria to infect their host resulting in diseases such as bacterial gastro-enteritis.
Cilia are present in large numbers but are shorter structures, whereas flagella are fewer and longer, whip-like structures. Cilia typically have a 9+2 microtubular structure, while in flagella they may be 9+2 or 9+0 in some cases. Cilia- are involved in movement and sensory functions whereas flagella- are mainly involved in the propulsion of cells in a fluid environment.
Cilia are involved in moving, fluids, and sensory, and can be seen as important in functions such as mucus removal in humans and the movement of eggs within the female reproductive tract in animals. It mainly plays the role of propelling cells and thus the sperm cells can move towards the egg during the process of fertilization and some of the members of the kingdom Protista.
