cellkärna

Cellkärna, often referred to as the nucleus, is a membrane-bound organelle found in eukaryotic cells. It is the central control center of the cell, housing the genetic material in the form of DNA. This DNA is organized into chromosomes, which contain the instructions for all cellular activities and the inheritance of traits. The nucleus is enclosed by a double membrane called the nuclear envelope, which separates its contents from the cytoplasm. This envelope is perforated by nuclear pores that regulate the passage of molecules between the nucleus and the cytoplasm, such as messenger RNA and proteins.

Within the nucleus, the nucleolus is a distinct structure responsible for ribosome synthesis. Ribosomes are essential for protein production in the cell. The liquid substance filling the nucleus is called the nucleoplasm, which contains chromatin (the complex of DNA and proteins) and other nuclear components. The cellkärna plays a critical role in cell division, growth, and differentiation by controlling gene expression and DNA replication. Its presence is a defining characteristic of eukaryotic organisms, distinguishing them from prokaryotic cells which lack a nucleus.