Final answer:
Flagella are long, whip-like structures used for cell movement, and are more common in bacteria, where they act like propellers. Eukaryotic flagella are rare and have a complex 9+2 microtubule structure. Cilia are shorter, more numerous, and serve different functions such as moving mucus in the respiratory tract or ova in the fallopian tubes.
Step-by-step explanation:
Flagella are crucial cellular structures used by some single-celled and multi-celled organisms for movement. In bacteria, flagella function like propellers; they are composed of flagellin protein subunits and extend outward from the cell, spinning to propel the bacteria forward. The structure is often described as whip-like due to its appearance and motion. In eukaryotic cells, flagella are less common, but when present, they typically consist of one or a few long, hair-like structures that extend from the plasma membrane, aiding in locomotion. For instance, sperm and the protozoan Euglena use flagella for movement. The composition of a eukaryotic flagellum includes microtubules in a 9+2 arrangement, which is different from the simpler structure found in bacteria.
Cilia are shorter, hair-like structures that can be found on cells, serving different purposes compared to flagella. For example, cells lining the fallopian tubes have cilia that move the ovum toward the uterus, while the cilia lining the respiratory tract serve to move mucus and trapped particulate matter toward the nostrils. Unlike flagella, when cilia are present, they are numerous and extend along the entire surface of the plasma membrane.
Specialized techniques such as flagella staining are required to visualize flagella under a light microscope due to their thin structure. This involves the application of mordant and dyes, such as tannic acid and pararosaniline, to thicken and stain the flagella, making them observable.