Question

Which of the following is not a part of bacteria flagellum? (a) Filament (b) Hook (c) Basal body (d) None

Short answer

The correct answer is (d) None. All the other options – Filament, Hook, Basal body – are all parts of a bacterial flagellum.

Step-by-step solution

Identifying Known Components

The known components of a bacterial flagellum are the filament, hook, and basal body. These three components play an essential role in the function of flagella, the locomotive component of certain cells.

Matching Known Components to Options

The options provided in the exercise are: (a) Filament, (b) Hook, (c) Basal body, and (d) None. All three known components are included in the options. Therefore, there doesn't seem to be an unknown component listed.

Reaching Conclusion

Since the components mentioned in options (a), (b), and (c) are all known parts of a bacterial flagellum and no other options are given, the only possible answer is option (d): None.

Key concepts

Filament

The filament is one of the essential parts of the bacterial flagellum. It is the long, whip-like structure that extends outward from the cell body. The primary role of the filament is to function as a propeller, allowing the bacterium to move through its environment. This structure is crucial for the motility of bacteria, enabling them to swim toward nutrients or away from harmful substances.

The filament is primarily composed of a protein called flagellin, which assembles into a helical shape. This helical structure enables the filament to spin and propel the bacterium forward. Imagine a tiny propeller that continuously rotates to push the bacterium through liquid.

The filament is impressively strong and flexible, capable of rotating very fast, sometimes at several hundred revolutions per second. Despite its simplicity, the filament plays an indispensable part in bacterial locomotion and survival.

Hook

The hook is a crucial connector in the bacterial flagellum. It acts as a coupling junction that links the filament with the motor components of the flagellum situated at the base. This hook structure is slightly bent, which gives it the ability to transmit torque generated by the motor to the filament.

Located at the proximal end of the filament, the hook allows for a smooth transition between the rotating base and the propelling filament. This ensures that the rotational energy is efficiently converted into movement, allowing the bacterium to navigate its environment effectively.

Much like a universal joint, the hook maintains the alignment of the rotating sections, enabling the filament to maintain its structure during high-speed rotation. Though less conspicuous than the filament itself, the hook is vital in ensuring the efficiency and directionality of bacterial movement.

Basal Body

The basal body serves as the anchoring structure of the bacterial flagellum, ensuring it is firmly attached to the bacterial cell membrane. It can be likened to the motor of the flagellum, facilitating the rotational movement of the filament.

The basal body penetrates the cell membrane and extends into the cell wall, securing the flagellum's stability. It consists of several rings that work together to generate and transmit rotational motion to the hook and filament. These rings are not only supportive but are also part of the flagellum's power source.

The energy required to drive the flagellar motor comes from a proton gradient. Movement is powered by the flow of protons across the cell membrane, making the basal body an essential hub for both mechanical support and energy conversion. Without this intricate and efficient system, the bacterial flagellum would be unable to function correctly. The basal body is thus critical for the bacterium's ability to move and adapt to its environment.