Final answer:
Nucleotides such as ATP and GTP are vital for the assembly and dynamic instability of actin filaments and microtubules, affecting cellular movement and stability. ATP is needed for actin filament assembly and myosin-driven muscle contraction, while GTP is involved in microtubule polymerization vital for cellular transport and division.
Step-by-step explanation:
The role of nucleotides such as ATP/GTP in actin filaments and microtubules is critical for various cellular processes. In actin filaments, ATP is required for the assembly of G-actin monomers into the F-actin polymer. The microfilament, composed of actin, uses ATP to enable cell movement through motor proteins like myosin. This is particularly evident in muscle cells where actin and myosin interact to cause muscle contraction. As for microtubules, GTP-bound tubulin monomers polymerize to form the microtubules, which serve as tracks for vesicles and organelles within the cell and are essential during cell division to ensure proper chromosome segregation.
ATP and GTP binding to the monomers also imparts polarity to the polymers, with a '+' end where subunits are added more rapidly and a '-' end where depolymerization predominates. In actin filaments, ATP hydrolysis to ADP reduces the binding affinity between the monomers, leading to a dynamic instability essential for functions like cellular movement. Therefore, nucleotides not only initiate filament assembly but also maintain the dynamic nature of these cytoskeletal elements essential for many cellular functions.