What are microfilaments primarily responsible for?

Microfilaments, which are composed of actin filaments, play a crucial role in maintaining the cell's shape, facilitating cellular movement, and supporting various cellular structures. They are a key component of the cytoskeleton, providing mechanical support to the cell and enabling processes such as muscle contraction, amoeboid movement, and the formation of cell extensions like microvilli.

In addition to providing structural integrity, microfilaments are involved in various cellular activities, including the propulsion of organelles and vesicles within the cell. Their dynamic nature allows for rapid assembly and disassembly, which is essential for processes that require changes in cell shape and motility.

The other options relate to functions that are not primarily associated with microfilaments. Transporting nutrients across membranes involves processes that rely more on proteins and channels in the membrane rather than the cytoskeletal elements. The storage of genetic information is the role of DNA within the cell’s nucleus, and manufacturing fuel for cellular respiration is conducted by organelles such as mitochondria rather than by microfilaments. Thus, the primary responsibility of microfilaments is indeed the movement and support of the cell.