What is Nucleoplasm ,chromosomes Nuclear Membrane

Nuclear Membrane

The nuclear membrane is a double-layered structure that encloses the contents of the nucleus. The outer layer of the membrane is connected to the endoplasmic reticulum.Like the cell membrane, the nuclear envelope consists of phospholipids that form a lipid bilayer.The envelope helps to maintain the shape of the nucleus and assists in regulating the flow of molecules into and out of the nucleus through nuclear pores. The nucleus communicates with the remaining of the cell or the cytoplasm through several openings called nuclear pores.Such nuclear pores are the sites for the exchange of large molecules (proteins and RNA) between the nucleus and cytoplasm.A fluid-filled space or perinuclear space is present between the two layers of a nuclear membrane.

Nucleoplasm

Nucleoplasm is the gelatinous substance within the nuclear envelope.Also called karyoplasm, this semi-aqueous material is similar to the cytoplasm and is composed mainly of water with dissolved salts, enzymes, and organic molecules suspended within.The nucleolus and chromosomes are surrounded by nucleoplasm, which functions to cushion and protect the contents of the nucleus.

Nucleoplasm also supports the nucleus by helping to maintain its shape. Additionally, nucleoplasm provides a medium by which materials, such as enzymes and nucleotides (DNA and RNA subunits), can be transported throughout the nucleus. Substances are exchanged between the cytoplasm and nucleoplasm through nuclear pores.

Nucleolus

Contained within the nucleus is a dense, membrane-less structure composed of RNA and proteins called the nucleolus.

Some of the eukaryotic organisms have a nucleus that contains up to four nucleoli.The nucleolus contains nucleolar organizers, which are parts of chromosomes with the genes for ribosome synthesis on them. The nucleolus helps to synthesize ribosomes by transcribing and assembling ribosomal RNA subunits. These subunits join together to form a ribosome during protein synthesis.The nucleolus disappears when a cell undergoes division and is reformed after the completion of cell division.

Chromosomes

The nucleus is the organelle that houses chromosomes.Chromosomes consist of DNA, which contains heredity information and instructions for cell growth, development, and reproduction.Chromosomes are present in the form of strings of DNA and histones (protein molecules) called chromatin.

 When a cell is “resting” i.e. not dividing, the chromosomes are organized into long entangled structures called chromatin.The chromatin is further classified into heterochromatin and euchromatin based on the functions. The former type is a highly condensed, transcriptionally inactive form, mostly present adjacent to the nuclear membrane.

 On the other hand, euchromatin is a delicate, less condensed organization of chromatin, which is found abundantly in a transcribing cell.

Besides the nucleolus, the nucleus contains a number of other non-membrane-delineated bodies. These include Cajal bodies, Gemini of coiled bodies, polymorphic interphase karyosome association (PIKA), promyelocytic leukemia (PML) bodies, paraspeckles, and splicing speckles.