Cell Biology and Structure

Within the nucleus is a small subspace known as the nucleolus. It is not bound by a membrane, so it is not an organelle. This space forms near the part of DNA with instructions for making ribosomes, the molecules responsible for making proteins.

The nucleolus is a non-membrane-bound structure within the nucleus, whereas mitochondria, plastids, and the endoplasmic reticulum are membrane-bound organelles found in the cytoplasm.

The nucleus is the most important and the largest component of the cell. Nucleus regulates the four main functions of the cell which are protein synthesis, cell division, growth and differentiation are carried out by the nucleus. Nucleus regulates all these cellular activities by controlling the enzymes required for cellular processes. Enzymes are proteins and protein synthesis is controlled by nucleus as mRNA required for protein synthesis is made from DNA which is situated in the nucleus.

Deoxyribonucleic acid (DNA) encodes the genetic instructions which are used in development and functioning of all living organisms. Ribonucleic acid (RNA) is one of the types of nucleic acid. Both, DNA and RNA are found in the nucleus. DNA is involved in coding the genetic information. It is present in the nucleoplasm of the nucleus in the tightly coiled form called as chromosomes. RNA is present in the nucleolus of the nucleus and involved in protein synthesis.
So, the correct answer is option A.

Nucleus is the membrane bound structure of the cell. It contains the majority of the cell's genetic material, i.e., DNA in the form of DNA-protein complex called as chromatin. DNA is present in the nucleoplasm of the nucleus in the tightly coiled form called as chromosomes. 
So, the correct answer is option A.

The nucleus is the largest and important part of the cell. It surrounded by the two layers of membrane. These membranes separates the nuclear content to get mixed with cytoplasm. Cytoplasm is the proteinaceous fluid in the cell which holds organelles like ribosomes, mitochondria, ER etc. Thus, the correct answer is option B.

A nuclear membrane, also known as the nuclear envelope, is a double lipid bilayer membrane, which surrounds the nucleus containing genetic material and nucleolus in eukaryotic cells. The nuclear membrane consists of two lipid bilayers- the inner nuclear membrane and the outer nuclear membrane and consists pores called as nuclear pores for the transportation of DNA, RNA and proteins. Thus, the correct answer is option B.

The nucleus controls the functioning of a cell. It is generally located in the center of the cell and is spherical in shape. It has a double-walled membrane which separates it from the cytoplasm. It contains the genetic material DNA and RNA in it. This porous membrane allows the transfer of material in the nucleus and cytoplasm. The nucleus contains a dense body called as nucleolus, which actually contains chromosomes, the genetic material. 

The nucleus is the membrane bound important structure of the cell. Nucleus regulates all the cellular activities by controlling the enzymes required for cellular processes. Enzymes are proteins and protein synthesis is controlled by nucleus as mRNA required for protein synthesis is made from DNA which is situated in the nucleus. It controls all the cellular activities and thus, called as brain of the cell.

Golgi apparatus is an organelle present in the cell and structurally possess series of compartments. Golgi apparatus has the main function of modifying, sorting and packaging the proteins which are synthesized by cells. Golgi bodies are also involved in the transport of lipid molecules across the cell. Golgi bodies also create lysosomes.  
Mitochondria produce the energy in the form of ATP of the cell. It consists its own DNA and called as mitochondrial DNA and not the DNA of the cell.
The nucleolus is the largest structure present in the nucleus. Ribosome synthesis and assemblage occurs in nucleolus region. The nucleus is bound with the double membrane in a eukaryotic cell in which most of the genetic material is present. The genetic material contains DNA and RNA. Thus, the correct answer is option D.

A eukaryotic cell has a nucleus bounded by a double wall membrane structure known as a nuclear membrane. The nuclear membrane is a discontinuous membrane having nuclear pores, which act as a protein channel for regulating the exchange of materials between cytoplasm and nucleoplasm. The gap between the inner and outer membrane is known as perinuclear space.

Chromatin is a complex of DNA and proteins that form chromosomes within the nucleus of eukaryotic cells. Nuclear DNA does not appear in free linear strands. 

A- As nucleus contains the genetic material responsible for hereditery. 

The eukaryotic endomembrane system has a nuclear membrane, endoplasmic reticulum, Golgi apparatus, plasma membrane and various small vesicles which are constantly reorganized and serve to segregate specific metabolic processes and to provide surfaces for enzyme-catalyzed reactions.
So, the correct answer is option A.

• Nucleus is a membrane-bound organelle containing the genetic material in the form of DNA molecule coiled to form the chromosomes.
  
• It is also known as the control centre of the cell.
• The DNA molecule gets transcribed into an mRNA template which is translated into a variety of proteins. 
  
• These translated proteins help in performing all the important functions within the cell.
• So, the answer is 'Nucleus'.