Question

Actin binding sites are located over
a. Troponin
b. Tropomyosin
c. Meromyosin
d. Creatinine
e. Both A and B

Answer 1

Hint: Muscle cells contain protein filaments of actin and myosin that slide past each other, causing a contraction that changes the length and shape of the cell. Thick and thin filaments cause contraction, namely myosin, actin, troponin, and tropomyosin. Actin may be a cellular protein found in microfilaments.

Complete answer:
Actin belongs to the family of globular multifunctional protein that is responsible for forming microfilaments in muscle fibers. The associated proteins alongside actin found in thin filaments are troponin and tropomyosin.
The myofibril consists of two sorts of filaments. they're thick filament(Myosin) and Thin filament(Actin).

An increase in Ca++ level results in the binding of calcium with a subunit of troponin i.e Troponin-C on actin filaments and thereby removes the masking of active sites for myosin. Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to make a cross bridge.

Each myosin (thick) filament is additionally a polymerized protein. Many monomeric proteins which are called Meromyosins constitute one thick filament. Each meromyosin has the globular head is a lively ATPase enzyme and has binding sites for ATP and active sites for actin.

Hence, the correct answer is option (C).

Additional information:
Troponin attaches to the protein tropomyosin and lies between actin filaments. Tropomyosin blocks the attachment site for the myosin head and prevents contraction during a relaxed muscle.

Creatinine may be a waste produced by muscles from the breakdown of a compound called creatine.

Meromyosin may be a part of myosin. With regards to human anatomy myosin and actin constitute the essential functional unit of a muscle cell, called sarcomere, playing a task in contraction.

Note: There are various applications of actin apart from helping in muscle contraction. In nanotechnology, Actin-myosin systems act as molecular motors that permit the transport of vesicles and organelles throughout the cytoplasm. Because of the dynamic ability of actin, it has been harnessed in several experiments including those carried out in acellular systems.
It is possible to determine the quality of certain processed foods such as meat, by quantifying the amount of actin present in the constituent meat. Actin is used as an internal control in western blots.