What is flagella: its types and function

 Flagella (singular: flagellum) are hair-like protrusions made of microtubules that stick out from the plasma membrane. They can be found on almost all types of cells. The name Flagellum means "Whip," and they look like whips. Most of the time, they are used to move a cell through a liquid. Their length is between 5 and 20 micrometers, and their width is between 10 and 30 nm.

How flagella came to be

People have looked at them for a long time. The first observations were made in the 1600s. But it wasn't until the 1800s that scientists figured out how flagella are made and what they do.

Theodor Schwann, a German biologist, said that all living things are made up of cells in 1837. This idea, which is still used today, became known as the "cell theory." Scientists like Matthias Schleiden and Rudolf Virchow also started to study the structures of cells around the same time.

Antonie van Leeuwenhoek, a German biologist, used one of his own microscopes to look at flagella on microorganisms in 1855. He saw that they moved like whips and thought that they were used to moving. This was the first time flagella were seen in living things.

At the end of the 1800s, scientists began to learn more about flagella. In 1887, a British biologist named Edwin Ray Lankester suggested that flagella are made of microtubules, which are a type of protein that make up the cell's skeleton. Later, other scientists, like the American biologist Albert Claude, who used electron microscopy in 1940 to show that flagella are made of microtubules arranged in a "9+2" pattern, confirmed this.

In the 1950s, American biologist George Palade used electron microscopy to figure out that the protein dynein is the molecular motor that moves flagella. This discovery was a big step forward in figuring out how flagella move because it showed that the movement is caused by dynein molecules moving together along the microtubules of the flagellum.

The endosymbiotic theory was made by the American biologist Lynn Margulis in the 1970s. This theory says that symbiotic relationships between prokaryotic cells and eukaryotic cells in the past led to the development of mitochondria and chloroplasts in eukaryotic cells, such as flagella. This theory is getting more and more evidence to back it up, and most scientists agree with it.

Changes in Flagella

A motor protein in the cell membrane gives flagella the power to move. This protein gets the energy it needs to move the flagella from the cell's metabolism. This rotation lets the cell move forward or make a spiral or circle. Some bacteria can also change how their flagella spin, which helps them move in a coordinated and effective way.

Algae, which are eukaryotes, use flagella to move and move their cells into the right place for photosynthesis. During fertilization, sperm cells use their flagella to move around and move toward an egg cell. Some protozoa move with flagella, and others move with cilia, which are like flagella but shorter and more numerous. Both flagella and cilia move in waves that are controlled by a process called "power stroke." This makes it possible for the cell or organism to keep going. Microtubules are the building blocks of both flagella and cilia.

Both bacterial and animal cells have flagella.

Both prokaryotic and eukaryotic cells have flagella. The diameter of flagella is the same as that of cilia, but eukaryotic flagella can be anywhere from one micrometer to several millimeters long. The flagella of prokaryotes spin, and with the help of a corkscrew-shaped filament, they move the cell forward. For example, bacterial flagella. Flagella of different types of bacteria are made of different sets of proteins and move in different ways. Bacteria can have one flagellum or many. They can also be Peritrichous, which means that they have more than one flagellum, or Polar, which means that they only have one flagellum (At a spot one or several flagella are present). The flagellum of a bacterium is made up of three parts: the filament, the base, and the hook.

References 

flagella flagellum an overview