Question

The monomeric actin is called as
A. F-actin
B. M-actin
C. G-actin
D. N-actin

Answer 1

Hint: In muscles we get a thin filament known as Actin.
It is a type of polymer made of many monomers.
The monomers of actin are globular in shape and hence called Globular-actin or G-actin.
It plays a major role in contraction and relaxation of muscles.

Complete answer:
Muscle tissue contains something called muscle fibers.
Muscle fibers are composed of a single muscle cell.
A characteristic feature of muscle fibre is the presence of a large number of parallel arranged filaments in sarcoplasm called myofibrils.
A complete study of myofibrils has accepted that the striated appearance is due to the distribution pattern of two important proteins:
1. Actin
2. Myosin.
Each actin filament or thin filament is made up of two filamentous actins that are helically wound to each other.
Each ‘F’ actin is a polymer of monomeric globular or G ACTINS.
Two filaments of tropomyosin also run close to the F- actins throughout its length.
A troponin is distributed at regular intervals on the tropomyosin.
In resting state a subunit of troponin masks the active binding sites for myosin on actin filament.
F- Actin is known as filamentous actin whereas G- actin is known as globular actin.
So, according to the question, monomeric action is called F- actin.

So, the correct option is option C. G- actin or globular actin. 

Note: Myosin filament or a thick filament is also a polymerized protein.
Many monomeric proteins known as meromyosins constitute one thick filament.
Each meromyosin has two important parts, a globular head with short arms and a tail.
The former being called heavy meromyosin and latter is called light meromyosin.