Occasional connections occur between the outer and inner membranes forming the nuclear pores. The nuclear pores help regulate flow of materials between the nucleus and the cytoplasm and serve as attachment points for chromatin fibers. Ribosomes These are organelles on which protein synthesis occurs. Also, small numbers of ribosomes resembling those of prokaryotes occur in mitochondria and chloroplasts. The cytoskeleton is a network of filaments developed in eukaryotes to move components within the cell as well as the cell as a whole.
Microtubules form part of the mitotic spindle that moves the chromosomes during cell division.
Microtubules also form the core of motile appendages known as cilia and flagella. Actin filaments also generate movement within the cytosol of eukaryotes. Actin filaments generate bulk movement of the cytoplasm know as cytoplasmic streaming, as well as a crawling type of locomotion of the cell as a whole. They also move plasma membrane during cell division. Intermediate filaments provide important structural support and anchoring in the cytoskeleton.