Question 1

What is a sarcomere?

Accepted Answer

A sarcomere is the contractile region of a myofibril between two successive Z lines. It contains thin actin filaments, thick myosin filaments, and associated proteins that produce contraction during muscle movement.

Question 2

What changes when a skeletal muscle contracts?

Accepted Answer

Thin actin filaments slide over thick myosin filaments toward the centre of each sarcomere. The I bands and H zone shorten, while the A band remains essentially unchanged because the length of the thick filaments does not change.

Question 3

What starts the actin-myosin interaction in skeletal muscle?

Accepted Answer

Release of calcium ions from the sarcoplasmic reticulum initiates the interaction. Calcium allows the actin-myosin contraction machinery to become active within the sarcomere.

Question 4

How do a cilium and a flagellum differ?

Accepted Answer

Cilia are generally short, numerous and work like oars. Flagella are comparatively longer, fewer and produce a whip-like movement, such as the movement of a sperm tail.

Question 5

What does the 9+2 arrangement indicate?

Accepted Answer

It indicates nine peripheral microtubule doublets surrounding two central microtubules in a typical eukaryotic cilium or flagellum. The organized axoneme generates bending when its dynein components use ATP to produce relative sliding.

Sarcomere to Movement 3D Lab — Muscle Fibre, Cilia and Flagella

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Practice