Cell Biology and Structure

The cortex is the outermost layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. In plants, it is composed mostly of differentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells often acquire irregularly thickened cell walls, and are called as collenchyma cells. Some of the outer cortical cells may contain chloroplasts but usually these cells lacks chloroplast. It is responsible for the transportation of materials into the central cylinder of the root through diffusion and may also be used for food storage in the form of starch. cortex, in plants, tissue of unspecialized cells lying between the epidermis and the vascular or conducting, tissues of stems and roots.
Cortical cells may contain stored carbohydrates or other substances such as resins, latex, essential oils, and tannins. Cells of cortex are living and contains nucleus and nucleolus.
Thus, the correct answer is option A.

• Minerals crystals are found in plant cell walls in the form of calcium oxalate, carbonate or silica.
  
• Cystoliths refers to the deposition of calcium carbonate in the epidermal cells of leaves of the plants belonging to the genus Acanthaceae and Urticaceae (stinging nettles).
• So, the correct answer is 'Cystoliths'.

In the eukaryotic cell, the nucleus is separated from the cytoplasm by a double lipid bilayer membrane known as a nuclear membrane. It encloses the genetic material of a cell. It is also known as karyotheca.

A eukaryotic cell has a nucleus bounded by a double wall membrane structure known as a nuclear membrane. The nuclear membrane has nuclear pore that regulates the exchange of materials between cytoplasm and nucleoplasm. The nucleus contains the chromatin threads and the nucleolus. The gel-like texture of the nucleoplasm embedded with chromatin threads gives it a dense appearance.

The DNA is the genetic material of the organism which is present in the nucleus. The DNA is bound to the histone proteins and packaged in the nucleus. The DNA contains the segments of genes which encode for the proteins. This genetic information is present in the nucleus of the living cells. 

DNA is stored in the nucleus, while proteins are assembled from free amino acids in the cytoplasm in structures called ribosomes.

Nucleus and mitochondria are double membrane-bound organelles while ribosome is not membrane bound. Prokaryotes are the organisms that lack any membrane-bound organelles which means that out of given options, only ribosomes are present in them. 

The nucleus is the largest and most significant living organelle of the cell. All the cellular activities of the cell are regulated by the nucleus. Hence it is called brain or control centre of the cell. The nucleus is surrounded by a double unit membrane from all sites. The chromosomes and genes which have genetical characters and transmit from one generation to another are found in the nucleus. Thus option D is the correct answer. 

The nucleus is an important cell organelle. It is the repository of genetic material. Inside nucleus, there is a synthesis of mRNA which is subsequently transported to the cytoplasm for protein synthesis. Thus, nucleus controls proteins synthesized in a cell and also is a repository of genetic material. Hence, the nucleus is controlling centre of the cell.

Nucleo-lemma is a term used in parallel with plasma-lemma. The nucleo-lemma is a part of the nuclear membrane. The outer membrane may have ribosomes and interconnections with ER. Nuclear membrane has a large number of pores for the nucleo-cytoplasmic exchange of materials.

Prokaryotic cells like bacteria have a single circular DNA molecule as their genetic material which is also called as a bacterial chromosome. The eukaryotic cells have a prominent nucleus with species-specific number of linear chromosomes having well-defined centromere and telomeres.

• The nucleus controls protein synthesis and is the genetic repository of a cell. 
• Hence, the nucleus can be called as the mastermind of cell.
• Thus, option C is correct.

The nucleus is a membrane-bound structure which is separated from the cytoplasm. This membrane is a nuclear membrane which has small pores which allow diffusion. The nucleolus is the centre dark part of the nucleus which is not surrounded by any kind of membrane. It is distinguished from nuclear material by its colour only.