Cilia and flagella are hair-like appendages arising through the surface of the living cell and differ from each other in size, number and beating. Cilia are short hair like locomotory organelle present in large numbers in a cell, whereas flagella are long hair like complex structure, which are few per cell.
Both locomotory organelle are an extension of the plasma membrane of the cell. Besides locomotion, they also help in some other processes such as circulation, respiration and excretion. They also help in capturing food. Both cilia and flagella are found in eukaryotic cells, but flagella are also present in prokaryotic cells. These appendages are not found in the prokaryotic cells.
Contents
Comparison Chart
| Basis for Comparison | Cilia | Flagella |
| Definition | Cilia are hair-like appendages that line the surfaces of certain cells and beat in a wave-like motion and act as locomotory organs. | Flagella are a threadlike structure that lines the surface of organisms and enables them to move. |
| Etymology | A Latin word which means “eyelash.” | A Latin word which means” whip.” |
| Found in | Eukaryotic cells | Both prokaryotic and eukaryotic cells |
| Occurrence in the cell | Occurs throughout the cell surface | Present at one end or two ends or all over the surface |
| Density | Numerous (hundreds) per cell | A few (less than 10) per cell |
| Length | Short and hair-like organelle (5 to 10µm) | Long wipe like organelle (150µm) |
| Type of locomotion | Rotational motion like a motor | Wave like sinusoidal and undulating movement |
| Beating | In coordination | Independently |
| Protein | Present | Absent |
| Energy Production | Cilia use “kinesin” which has an ATPase activity that produces energy to perform the movement | Flagella are powered by the proton-motive force by the plasma membrane |
| Types | Two types: motile and non-motile cilia | Three types: bacterial flagella, archaeal flagella and eukaryotic flagella |
| Function | Locomotion, respiration, excretion and circulation | Locomotion, respiration, excretion and circulation |
| Example | Cilia present in Paramecium | Flagella present in Salmonella |
What are Cilia?
This word is derived from Latin and pronounced as “silly-ah” which is the plural form of the cilium. It means “eyelash.” Cilia are short, slender, hair-like appendages arising from the surface of the cell. The width of the cilia is less than 1µm and the length varies from 1 to 10µm. These are part of almost all eukaryotic cells and play a significant role in cell development. They are most active during the cell cycle progression and proliferation. Organisms having cilia move very fast and more efficiently. Researchers have discovered that WBCs move similarly. When any injury appears in the body, WBCs traverse the blood vessels with the help of cilia.
Types
Cilia can be divided into two types; motile and non-motile. Motile or moving cilia are present in the lungs, middle ear and respiratory tract. These cilia can be found in both single-celled eukaryotes and higher humans. These types of cilia beat rhythmically. Their role is to keep the airways clear of mucus and dust because of which it is calm to breathe freely and without any irritation. They also help in the locomotion of sperm. In the fallopian tube, cilia serve to move the ovum to the uterus.
Nonmotile cilia also known as primary cilia, play a role in receiving messages from other cells or nearby fluids by acting as the antenna for the cells. In the kidney, the cilia send messages to the cells about the flow of the urine. In the eyes, non-motile cilia support the transportation of vital molecules from one end of the photoreceptor of the retina to the other.
What are Flagella?
It is pronounced as “fla-gel-ah,” and it is the plural of the flagellum. Flagella is derived from the Latin word, which means “whip.” Flagella are hair-like complex filamentous structure extending through the cell surface. Their main functions are adhesion, signal transduction, sensation and movements.
Flagella are made up of a specific protein called flagellin, which is embedded in the cell envelope. Flagella’s body consists of Hook, filament and the basal body. The hook is the cell envelop, the filament is the outer part of the cell and the basal body is attached to the cytoplasmic membrane through the ring-like structure. Flagella’s body movement is powered by the proton motive force of the plasma membrane.
Types
Flagella are broadly categorized into three types; bacterial flagella, archaeal flagella and eukaryotic flagella. Bacterial flagella are present in Salmonella typhi and E-coli. These can be one, two or many flagella per cell. These have the helical filamentous structure, which rotates like a screw and provides motility to the bacteria. Archaeal flagella are the same as bacterial flagella in structure but lack a central channel. Eukaryotic flagella are the complex projections that move back and forth. An example of this type of flagella is the sperm cell, which propels itself through the female reproductive tract by using its flagellum.
Key Differences
- Cilia are microscopic, slender, short hair-like structures whereas flagella are long and few in number, complex, filamentous structure.
- Cilia are present overall on the surface, whereas flagella are extended through the cell surface.
- Cilia are present only in the eukaryotic cell, whereas flagella are found in both prokaryotic and eukaryotic cell.
- Cilia beat very fast in coordinately and rotational motion, whereas flagella beat slow in the whip-like sinusoidal, undulating and independent movement.
- Cilia are helpful in locomotion, aeration, excretion, circulation, whereas flagella are helpful in locomotion only.
Key Similarities
- Both cilia and flagella arise from the small granular structure called the basal body.
- Both are an outgrowth of the plasma membrane of the cell.
- Both consist of the central filament called an axoneme.
- Both cilia and flagella serve as locomotory organs.
- Both help in capturing food in protozoans and metazoans.
- Both also help in respiration, circulation and excretion.
Conclusion
In conclusion, cilia and flagella are two different types of locomotory organelles of prokaryotic and eukaryotic cells. Besides this, they also perform certain other physiological processes such as circulation, respiration, excretion and locomotion. Both are the same structure but differ from each other in their number, size and beating mode.