Question:
In the resting muscle fibre, tropomyosin partially covers
In the resting muscle fibre, tropomyosin partially covers
Updated On: Jun 14, 2022
- calcium binding sites on troponin
- actin binding sites on myosin
- Myosin binding sites on actin
- calcium binding sites on actin
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The Correct Option is C
Solution and Explanation
Tropomyosin is an actin-binding protein that regulates actin mechanics. It is important, among other things, for muscle contraction. Tropomyosin, along with the troponin complex, associate with actin in muscle fibres and regulate muscle contraction by regulating the binding of myosin. In resting muscle, tropomyosin overlays the myosin binding sites on actin, with a single tropomyosin molecule spanning seven actin subunits and is "locked" down in this position by troponin-T (tropomyosin binding troponin) and troponin-I (inhibitory troponin). Upon release of calcium from the sarcoplasmic reticulum, calcium binds to troponin-C (calcium binding troponin). This "unlocks" tropomyosin from actin, allowing it to move away from the binding groove. Myosin heads can now access the binding sites on actin. Once one myosin head binds, this fully displaces tropomyosin and allows additional myosin heads to bind, initiating muscle shortening and contraction. Once calcium is pumped out of the cytoplasm and calcium levels return to normal, tropomyosin again binds to actin, preventing myosin from binding.
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Concepts Used:
Locomotion and Movement
Locomotion
The movement of a creature from one place to another is known as locomotion. During the process, there is the action of appendages such as wings, limbs, and flagella. In some animals, like fish, whales, and sharks, locomotion upshots from a wave-like series of muscle contractions. Locomotion helps an organism in finding their food, avoid harsh weather conditions, escape from their predators, etc.
Some examples of locomotion are walking, running, swimming, etc. Movement, on the other hand, refers to any type of motion that need not be localized.
Read More: Locomotion and Movement
Movement
Movement is generally described as a state of changing the position from rest to motion or vice-versa. Movement can be both voluntary movement and involuntary movement. Movement helps an organism perform essential functions, such as pumping blood to the different parts of the body, etc.
Read More: Difference between Locomotion and Movement