Question

Number of dynein arms is:
(a) Four attached to subfiber B
(b) Two attached to subfiber B
(c) Two attached to subfiber A
(d) Four attached to subfiber A

Answer 1

Hint: Dynein moves along the microtubules in the cells and is a family of cytoskeletal motor proteins. It can convert the chemical energy that was stored in ATP into mechanical work, provides forces, transports various cellular cargos, and plays a role in mitosis.

Complete answer:
All eukaryotic cilia and flagella are similar in their organization possessing a central bundle of microtubules known as the axoneme. The central pair of singlet microtubules is surrounded by the nine outer doublet microtubules. When the axoneme is viewed from the cross- section under the electron microscope a characteristic nine plus two arrangement of microtubules is seen. Each of the doublet microtubules consists of subfibers or ‘A and B’ tubules. The A with 13 protofilaments is the total number of microtubules and the B tubule has 10 protofilaments. The plasma membrane surrounds the axoneme which comprises the bundle of microtubules. The axoneme of the organism or cell type is always 0.25 micrometers in diameter but the length may vary from a few micrometers to 3 mm.

So, the correct answer is 'Two attached to subfiber A'.

Note:
- The protein in charge of the movement was first discovered in 1963 and named dynein. 20 years down the line, cytoplasmic dynein was isolated and identified, this had been taught to exist since the identification of flagellar dynein.
- The movement of organisms from one place to another place is known as locomotion. Locomotory organelles found in protozoa are mainly of five types and they are Pseudopodia Locomotion, Flagellar Locomotion, Ciliary Locomotion, Wriggling Locomotion, and Locomotion by Mucilage Propulsion. So cilia and flagella are used in locomotion.