The key difference between flagella and cilia is that the flagella are long and present in one to eight per cell while the cilia are short and present in hundreds per cell.
Cilia and Flagella are tiny structures attached to eukaryotic and prokaryotic cells. They protrude from the surface of their cells. These structures help in locomotion of unicellular organisms. Accordingly, they mainly contain proteins called microtubules or basal bodies. In the case of single-celled eukaryotic organisms, both cilia and flagella are vital for the locomotion. On the other hand, in multicellular organisms, cilia and flagella help in the movement of fluids and other materials along the body tubes while performing the function of moving a cell or a group of cells. However, there is some difference between flagella and cilia; especially, they differ from each other by the length, size, appearance and type of cells to which they are attached.
CONTENTS
1. Overview and Key Difference
2. What are Flagella
3. What are Cilia
4. Similarities Between Flagella and Cilia
5. Side by Side Comparison – Flagella vs Cilia in Tabular Form
6. Summary
What are Flagella?
Flagella are whip-like unbranched extensions that grow out from the cell body. Structurally, there are three main parts of a flagellum namely filament, hook and basal body. Furthermore, they are longer than cilia, and one cell contains a few flagella. However, the number of flagella varies from one to eight among the cells. Also, they are predominantly present in prokaryotic cells such as bacteria. In humans, they are abundant in gametes.
Figure 01: Flagella
Usually, flagella come out of the cell from one point and show wave-like or undulating movements. But, in bacteria, the number and their arrangements are different. Based on the number and the arrangement, some bacteria are monotrichous while some are amphitrichous, lophotrichous and peritrichous as visible in figure 01.
What are Cilia?
Cilia are tiny hair-like extensions that protrude from the cell body. They are shorter than flagella. Also, they are present in large numbers per one cell. Furthermore, they can be seen mainly in eukaryotic cells such as protozoa, fungi, macrophages, yeasts, sperm cells, white blood cells and in the respiratory tract of humans, etc. In human beings, the respiratory tract contains many of these that prevent the entrance of dust, smog and other harmful materials to lungs.
Figure 02: Cilia
Besides, there are two types of cilia; they are the motile or nonmotile (primary) cilia. Nonmotile cilia provide a sensory function while the motile cilia help in locomotion.
What are the Similarities Between Flagella and Cilia?
- The flagella and cilia are tiny structures which are microscopic.
- They are cell appendages and consist of microtubules.
- Primarily, they are made up of proteins.
- Furthermore, they are thread-like structures that protrude from the surface of the cells.
- Besides, the main function of both is in helping the locomotion.
- Meantime, flagella and cilia are also considered as organelles.
- Also, they have very similar structures that arrange in 9+2.
What is the Difference Between Flagella and Cilia?
Cilia and flagella help microorganisms; especially, prokaryotic and unicellular eukaryotic organisms, in their locomotion. However, the key difference between flagella and cilia is that the cilia are short while the flagella are long. Appearance wise, one other difference between flagella and cilia is that the cilia are hair-like while the flagella are whip-like protrusions. Furthermore, many cilia (hundreds of) are present in one cell while few flagella (one to eight) are present in one cell. Hence, this is another difference between flagella and cilia.
Functionally, there are some more differences between flagella and cilia. The below infographic on the difference between flagella and cilia provides more details about these differences.
Summary – Flagella vs Cilia
Flagella and cilia are two similar types of thread-like structures found on cells. However, we can identify some difference between flagella and cilia based on their length, size, appearance, and the associated cells. Among all, the key difference between flagella and cilia is that the flagella are longer than cilia and present in one to eight per cell but, cilia are shorter than flagella and present in hundreds in one cell.
Furthermore, flagella are whip-like structures while cilia are tiny hair-like structures. Also, flagella are predominantly found in prokaryotes while cilia are predominantly visible in eukaryotic cells. Thus, this summarizes the difference between flagella and cilia.
Reference:
1.“Cilium.” Wikipedia, Wikimedia Foundation, 27 Nov. 2018. Available here
2.“Flagellum.” NeuroImage, Academic Press. Available here
Image Courtesy:
1.”Flagella”By Adenosine – Own work, (CC BY 3.0) via Commons Wikimedia
2.”Blausen 0766 RespiratoryEpithelium”By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work, (CC BY 3.0) via Commons Wikimedia