Cilia and Flagella are the cell organelles meant for the movement of the cells or substances.
Cilia are short, slender, hair-like structures present on the cell surface of protozoan and mammalian cells.
Flagella are long, thread-like structures protruding out of the cell wall from the cytoplasm.
Cilia are also found in unicellular organisms like bacteria and protozoa.
In higher animals, they are found in the respiratory system, digestive system, reproductive system, and urinary system.
Cilia and Flagella are cell organelles that look similar, but they have a wide range of differences
| Sl. No | Characteristics | Cilia | Flagella |
|---|---|---|---|
| 1 | Appearance | They are short, slender, and hair-like structures. | They are long, filamentous, and thread-like structures. |
| 2 | Occurrence | Present all over the cell surface | Seen at one or two ends and rarely all over the cell. |
| 3 | Dimensions | Ranges from 1-10µm in length and less than 1µm in width. | Between 5-20 µm in length and 10-30nm in width. |
| 4 | Density | Numerous | Very few or sometimes only one is present. |
| 5 | Found in | Only in Eukaryotes and are absent in bacteria. | Seen in both Eukaryotes and Prokaryotes. |
| 6 | Distribution | Present in protozoa. Larvae of Annelids, Molluscs, Echinodermates, and Platyhelminthes. And also in the epithelium of mammals. | Present in choanocyte of sponges, Algae, Spermatozoa and gamete cells. |
| 7 | Function | Locomotion, circulation, aeration, signal transformation, excretion. | Locomotion and also for adhesion in the host. |
| 8 | Types | 1. Primary, non- motile cilia (seen in almost all the cells). 2. Motile cilia are seen in paramecium, Respiratory passages, the middle ear, etc. | 1. Bacterial flagella. 2. Archaeal flagella 3. Eukaryotic flagella. |
| 9 | Types of motion | 1. Fast-moving, rotational, show back and forth beating. 2. Show rhythmic, coordinated movement. 3. Ciliary movement sweeps materials across tissues. | 1. Slow-moving, propeller-like motion, undulating, sinusoidal movement. 2. Show independent movement. 3. Flagellar movement propels cells forward |
| 10 | Energy source | Uses ‘kinesin’, which has ATPase activity | Obtain energy from the Proton motive force of the plasma membrane. |
| 11 | Presence of Nexin | Nexin protein is absent | Nexin protein is present between the tubules to hold them together. |
| 12 | Examples | Cilia is present in paramecium. | Flagells is present in euglena. In bacteria like Escherichia coli, Pseudomonas aeruginosa |
Ciliary functions vary in different organisms.
- Besides locomotion, they are used for the movement of substances like expelling particulate matter in the respiratory tract and propulsion of food in the gut.
- Further, they are involved in signal transformation in sensory cells like in the tongue.
Variations in the internal structure of Cilia and flagella.
The design of cilia is different in Motile and not motile cilia.
Motile cilia contain an outer membrane that encloses cilia and
fuses with the cell wall at the base.
The inner space contains a fluid matrix and has microtubules. There are 9 fused microtubule doublets that surround 2 single central microtubules (9+2).
This arrangement is collectively known as an axoneme.
Microtubule doublet contains ‘A’ tubule and ‘B’ tubule. ‘A’ tubule is a complete tubule with 13 protofilaments. The ‘B’ tubule is complete with 10 protofilaments.
However, primary or non-motile cilia have a matrix that contains 9 fused microtubules only (9+0). There is no central tubule.
On the other hand, the eukaryotic flagella show similar internal morphology to the motile cilia of eukaryotes.
It contains an ‘axoneme,’ which has a 9+2 microtubule arrangement.
Whereas the prokaryotic flagella do not have a 9+2 arrangement of microtubules.
Prokaryotic flagella are made of a protein called Flagellin and are thinner compared to eukaryotic flagella.