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The main difference between cilia and flagella is that cilia are a short hair-like structure that is present large in number in a cell whereas flagella are a long hair-like structure that is few in a cell.
Cilia vs. Flagella
Cilia and flagella are the organelles of the cell that are structurally similar but vary in their function and size etc. They both are the appendages of the plasma membrane of the cell and arise from the basal body. They are locomotory in structure. Cilia also play an important role in many other processes like excretion, respiration, circulation and in capturing food, etc. Cilia is short in structure and present in a eukaryotic cell only while flagella are long in structure and present in both prokaryotic and eukaryotic cell. There beating pattern is also different, cilia beat in coordination with each other while flagella beat independently to each other.
What is Cilia?
Cilia is derived from a Latin word which means “eyelash.” It is a short, slender and hair-like appendage found throughout the surface of the cell. Its width is less than 1 µm and is around 5 to 10 micrometer in length.
- Motile Cilia: They are moving cilia that are mainly found in the lungs, middle ear, and respiratory tract. They beat rhythmically and keep the airways clear of mucus and dust to make it easy to breathe freely and without any irritation. They also help in the movement of the sperm. Motile cilia have 9+2 arrangement of the ciliary axoneme that is the microtubular backbone of the cilia and is surrounded by the plasma membrane. There are nine fused pairs of microtubules arranged in a circle, and the two unfused microtubules are present in the center of the circle. The arms “dynein” are also attached to the microtubules that act as the molecular motors. Any defect in the dynein arms may cause male infertility and problems in the respiratory tract.
- Nonmotile Cilia: It is also known as primary cilia. It acts as the antennae of the cell and plays its role in receiving signals from other cells or nearby fluids. For example in the kidney, they send signals about the flow of the urine. These cilia have 9+0 microtubular arrangement.
What is Flagella?
The word flagella are derived from the Latin word which means “whip.” They are lash-like, complex organelles extending through the cell surface. They are composed of flagellin protein, embedded in the cell envelope. They are also locomotory in structure. They can be about 150 µm in length and 12-30 nm in diameter. A cell may have a single flagellum on its pole or less than 10 per cell. Flagella also consist of Hook, Filament and Basal body in their body parts that help in adhesion, signal transduction, sensation, and movements, etc.
- Bacterial Flagella: According to the presence of flagella, the pattern of attachment and number of flagella present, bacteria are divided into different types. Atrichous is the bacteria without flagella; Monotrichous is a single polar flagellum, Lophotrichous is a tuft of flagella at a single-pole, Amphitrichous is a tuft of flagella at both ends and Peritrichous is a form in which flagella surrounds the whole surface. They have a helical filamentous like structure that rotates like screws. It is found in E.coli.
- Archaeal Flagella: It is similar to bacterial flagella but lacks a central channel.
- Eukaryotic Flagella: These are complex projections that beat back and forth. Its example is a sperm cell.
- A large number of microscopic, short and slender hair-like structures that cover the whole surface of the cell are called cilia whereas the long thread-like structure that is present few on the surface of the cell are called flagella.
- Cilia is present in a eukaryotic cell only; on the other hand, flagella are found in both prokaryotic cell and eukaryotic cells.
- Cilia are short in size there width is less than 1 µm, and is around 5 to 10 micrometer in length while flagella are long in size about 150 µm in length and 12-30 nm in diameter.
- Cilia are found numerous per cell. Conversely, there are few numbers of flagella, i.e., less than 10 per cell.
- Cilia beat in coordination to each other on the flip side; flagella beat independently to each other.
- Nexim (a protein) is present in cilia while it is absent in flagella.
- Cilia is present all over the surface of the cell whereas flagella are present on the poles and sometimes surrounds the whole surface.
- Cilia show rotational movement like a motor, i.e., they are very fast-moving while flagella show slow, sinusoidal, wave-like, and undulating movement.
- Cilia play an important role in locomotion and aeration (respiration), etc. but flagella are helpful in locomotion only.
- Cilia is present in Paramecium whereas flagella are present in Salmonella.
According to above discussion, it is concluded that cilia are a short locomotory appendage of the cell surface that also helps in aeration (respiration), etc. and found numerous per cell while flagella are a long locomotory structure that is found few per cell.