Saturday, December 7, 2013

Functions & Components of Nucleus

Functions of Nucleus
• Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm
• Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells

Components of Nucleus
– Nuclear envelope
– Nucleoplasm
– Nucleolus
– Chromosome
– Chromatin

Nucleus:
The nucleus is the defining organelle of eukaryotic cells. The nucleus is separated from the cytoplasm by a double membrane (two phospholipid bilayers); known as the nuclear envelope. The nuclear envelope controls the passage of molecules between the nucleus and cytoplasm. The nucleus contains the DNA, the stored genetic instructions of each cell. In addition, important reactions for interpreting the genetic instructions occur in the nucleus.
  • In the nucleus, DNA is organized into discrete units called chromosomes
  • Each chromosome is composed of a single DNA molecule associated with proteins
  • The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis
Nucleolus
  •  Dense mass of material in nucleus
  •  May be one or more
  •  Cluster of DNA and proteins
  •  Materials (mostly rRNA) from which ribosomal subunits are built
  • Subunits must pass through nuclear pores to reach cytoplasm