AP BIOLOGY

Detailed explanation-1: -Microfilaments are thin (7 nm) molecules composed principally of actin protein subunits, which polymerize to form elongated actin filaments (F-actin). Individual actin molecules, called G-actin, carry ATP to provide energy for the polymerization process.

Detailed explanation-2: -Final answer: Microfilaments are composed mainly of a protein called actin.

Detailed explanation-3: -The actin filaments in networks are held together by large actin-binding proteins, such as filamin (Figure 11.8). Filamin (also called actin-binding protein or ABP-280) binds actin as a dimer of two 280-kd subunits.