Problem 68 - Objective Biology for NEET

Question

Of all the parts of flagellum, which one is the longest? (a) Filament (b) Hook (c) Basal body (b) Fimbriae

Step-by-Step Solution

Answer

The longest part of a flagellum is the Filament (a)

Step 1: Understand the structure of a Flagellum

A flagellum consists of several parts, namely the filament, hook and basal body. The filament is an outermost, long, thin, helical structure. The hook is a short, curved segment that connects the filament to the basal body. The basal body is embedded in the cell envelope and forms the rotor of the flagellar motor. Fimbriae are not part of the flagellum but are other surface appendages found in bacteria.

Step 2: Identify the longest part

The filament is the longest part of the flagellum. It's what forms the whip-like structure that we can see. The hook and the basal body are much shorter than the filament, and fimbriae is not a part of the flagellum.

Key Concepts

Cell Biology

Cell biology is a branch of biology that studies the structure and function of cells, which are the basic units of life. Nearly every process that sustains life is carried out by intricate systems within cells. From replicating genetic material to responding to external stimuli, cells perform a vast array of tasks. Understanding cell biology is crucial for grasping how organisms grow, reproduce, and function on a fundamental level.

In the context of the flagellum structure, cell biology examines how different components of the cell, including flagellum, contribute to cell motility. This knowledge not only helps us understand how bacteria and similar organisms move but also how cells in multicellular organisms function in development and disease. For example, while human cells do not have flagella, the structure and function of cilia (which are similar to flagella) are pertinent to cell biology, affecting respiratory health and other bodily systems.

Bacterial Flagellum

The bacterial flagellum is a remarkable cellular appendage that provides motility to bacteria. Its structure is relatively simple yet highly specialized. It is usually divided into three main parts: the filament, the hook, and the basal body.

The filament is the longest part of the flagellum and is largely responsible for propelling the bacterium forward. It is a helical structure made up of a protein called flagellin and can measure up to ten times the length of the bacterial cell itself. The hook, a short and flexible region, connects the filament to the basal body, which acts as a rotary engine embedded within the cell membrane and cell wall. The energy to turn the basal body comes from a flow of ions across the bacterial cell membrane, highlighting the intricacy of these biological machines.

It is important to recognize the efficiency of the bacterial flagellum, which makes it a subject of interest not only in microbiology but also in bioengineering and nanotechnology. This remarkable structure demonstrates the symbiosis of biology and physics, as well as the evolutionary adaptations that enable organisms to thrive in diverse environments.

Microbiology

Microbiology is the scientific study of microorganisms, those being unicellular, multicellular, or acellular. This field involves investigating the biology of bacteria, viruses, fungi, and protozoa, many of which play critical roles in ecosystems, human health, and disease.

In microbiology, the study of the bacterial flagellum contributes to an understanding of bacterial motility, which has implications for both the progression of infectious diseases and the development of antibacterial treatments. Scientists study how the structural differences in flagella can affect the way bacteria navigate through various environments, including the human body. This knowledge can be particularly valuable in understanding how bacteria move to colonize surfaces, how they reach their sites of infection, and how they evade immune responses.

Given the role of the bacterial flagellum in motility, it is often a target for antibiotics and other antibacterial strategies. By obstructing flagellar assembly or function, it may be possible to hinder a bacterium's ability to cause infection. Moreover, microbiology also explores the role of flagella in biofilm formation, a common bacterial survival strategy that makes treating infections more complicated.