Nucleoplazma

Nucleoplazma, or nucleoplasm (also called karyoplasm), is the semi-fluid substance inside the cell nucleus, excluding the nucleolus. It fills the nuclear compartment and surrounds the chromatin and nuclear bodies. The nucleoplasm is bounded by the nuclear envelope and communicates with the cytoplasm through nuclear pore complexes, allowing selective transport of ions, nucleotides, and macromolecules.

The nucleoplasm contains water, dissolved ions, nucleotides, and a mixture of proteins including histones, polymerases, nucleases, and components of the nuclear matrix. Chromatin fibers are suspended within it and organized into euchromatin and heterochromatin, which regulate gene accessibility. The nucleolus resides within the nucleoplasm as a distinct substructure and is not part of the general nucleoplasmic milieu.

The nucleoplasm provides the medium for genetic processes such as transcription, DNA replication, RNA processing, and DNA repair. It hosts enzymes and ribonucleoprotein complexes required for these tasks and helps maintain nuclear architecture through the nuclear matrix. Molecules move between the nucleoplasm and cytoplasm via nuclear pores, a process that is regulated during the cell cycle and in response to cellular signals. During mitosis, the nucleus reorganizes and the nucleoplasm becomes partitioned with the disassembly and reassembly of the nuclear envelope.