Tag: biology

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.

Vaucheria is commonly known as “water felt”; the sparsely branched or unbranched coenocytic filaments often form feltlike mats. The often macroscopic cells contain a large number of discoid plastids, with or without pyrenoids. Reproduction occurs by zoospores, aplanospores, and akinetes.

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.

Nuclear membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus.

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 nucleus is the important structure of the cell and fully enclosed in a nuclear membrane. It contains the cells' genetic material organized as DNA and variety of proteins to form chromosomes. This is major site for cell reproduction. The genes are first transcribed, where DNA is read by RNA polymerase to produce messenger RNA (mRNA). The nucleus is therefore the site of RNA and DNA synthesis. Whereas protein is synthesized from the mRNA in the cytoplasm. Thus, the correct answer is option D.

Acetabularia consists of a rootlike holdfast, a long, cylindrical stalk; and a cuplike cap. The nucleus is present in the holdfast. Acetabularia exhibits regeneration of the cap after any injury. A. mediterranea has a smooth cap and A. crenulata, has a cap with fingerlike projections. Danish biologist J. Hämmerling and Belgian biologist J. Brachet performed grafting experiment on above mentioned species and showed that type of caps that regenerated were determined by the type of the donor species of the holdfasts, not by those donating the stalks. It was concluded, that nucleus in the holdfast of Acetabularia controls the shape of the caps. The correct answer is E.

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.