Difference Between 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:

Prokaryotic and Eukaryotic Flagella

Flagella are classified into two types:

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:

Similarities Between Cilia and Flagella

The following table summarises the similarities between cilia and flagella:

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

1. 9 + 2 pattern

2. 9 + 0 pattern

3. Both A and B

4. 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

1. Cilia

2. Microcilia

3. Flagella

4. 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:

1. Fimbriae

2. Flagella

3. Cilia

4. 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:

• MCQs on Flagella and Cilia

• Endomembrane System

• Golgi apparatus

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