Final answer:
Actin is a globular protein that polymerizes to form the filamentous F-actin, critical for microfilament structure and cellular functions including muscle contraction. The correct answer option 1 and 2.
Step-by-step explanation:
The question relates to the properties of actin and its polymerized form, F-actin, which are crucial for the structure and function of microfilaments in cells. Actin is a globular protein that can polymerize into filamentous form, known as F-actin, which is composed of two intertwined strands of actin monomers and is essential for muscle contraction and a variety of cellular movements.
Contrary to one of the options provided, actin is not only found in muscle cells but is present in many other cell types, where it performs a range of essential functions. F-actin is the filamentous form of actin, and while they are related, they are not the same thing; actin refers to the monomeric unit, while F-actin refers to the filamentous polymer.
Therefore, the correct statement about actin and F-actin is: 1) Actin is a globular protein that forms microfilaments. 2) F-actin is the filamentous form of actin. The incorrect statements are that actin and F-actin are the same thing and that actin is only found in muscle cells.