A centrosome comprises two centrioles that serve as microtubule organizing center (MTOC). Its function is to attach to the centromeres of sister chromatids, and separate them eqully into new cells during cell division.
The cytoskeleton is a network of filament proteins that extends throughout a cell. It gives cell shape, organizes organelles, involves molecule transport, cell division, cell signaling, and cell movement.
Endoplasmic reticulum (ER) is an internal membrane that forms branching networks of many interconnected sacs and tubes inside cells. Rough ER stays closer to the nucleus and coordinates protein synthesis. Smooth ER lacks ribosomes but specializes in lipid synthesis.
All living organisms fall into one of two categories: Eukaryotes (plants, animals, and fungi) or Prokaryotes (bacteria and archaea). Prokaryotes are unicellular organisms that don’t have a membrane-bound nucleus and other organelles.
Animal and plant cells are eukaryotic cells. They all have nuclei, cell membranes, and organelles (ER, Golgi, ribosomes, and mitochondria). The structures only in plant cells are the cell wall, chloroplast, and vacuole.