Which cytoskeletal components are primarily responsible for moving substances and organelles within the cytoplasm?

• A. Endoplasmic reticulum and Golgi apparatus
• B. Centrioles and cilia
• C. Microvilli and ribosomes
• D. Microfilaments and microtubules

Answer: (D)

Intracellular transport relies on the cytoskeletal filaments that form tracks for motor proteins to move cargo. Microtubules act as long, sturdy tracks along which motor proteins like kinesin and dynein carry vesicles, organelles, and other cargo through the cytoplasm. Microfilaments, made of actin, support shorter-range movements and work with myosin to shuttle smaller cargo and help with changes in cell shape and cytoplasmic streaming. Together, these two filament systems provide the dynamic network that moves substances and organelles where they’re needed.

Other structures listed serve different roles: the endoplasmic reticulum and Golgi apparatus are involved in protein and lipid processing and trafficking rather than forming transport tracks; centrioles organize microtubules and cilia move substances across a cell surface; microvilli increase surface area and ribosomes synthesize proteins.