Some organisms consist of single cells, whereas other organisms, like humans, contain trillions of cells. The study of cells, i.e, the structure and functions of cells, is called cell biology. Cells are the building blocks of living organisms. All cells have organelles, cell membrane, cytoplasm, and genetic material. Most cells are too small and cannot be seen without a microscope. There are two kinds of cells, eukaryotic and prokaryotic cells. Cells consisting of a nucleus are called prokaryotic cells, while cells that do not have a nucleus are called eukaryotic cells. There are many characteristics of cells, but some of the characteristics are most common for all cells. 

The common characteristics of cells can be observed based on the structure and function of cells.     

Structural characteristics of cell

 All the cells of living beings have the following common structural features:

Cytoplasm

The cytoplasm is a thick coagulated fluid covering each cell and enveloping the cell membrane. It contains water, salts, and various organic molecules. The cytoplasm is the place where metabolic processes can happen. For example, the splitting of glucose into energy takes place within the cytoplasm. 

Genetic material

Genetic material is the hereditary material in the cell; it brings all specific information to an organism. The genetic materials are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). 

• The genetic material deoxyribonucleic acid (DNA) exists within the nucleus of eukaryotic cells, and in prokaryotic cells, it exists in the nucleoid region. 
• The structure of DNA is composed of sugar chains (deoxyribose) that construct its backbone. Each sugar molecule is linked to a base molecule and phosphoric acid. The bases in DNA are Adenine (‘A’), Thymine (‘T’), Guanine (‘G’), and Cytosine (‘C’). The bases in RNA Adenine (‘A’), Uracil (‘U’), Guanine (‘G’), and Cytosine (‘C’).  
• The stored genetic code depends on the arrangement of bases within DNA, which represents a particular protein.

Ribosomes

 Ribosomes are composed of a protein complex and chains of ribonucleic acid (RNA). 

• In prokaryotic cells, ribosomes are independent structures . 70S ribosomes present in prokaryotics.In Eukaryotic organisms, most ribosomes have adhered to structures called the rough endoplasmic reticulum, which is linked with the nucleus. 80S ribosome present in cell except some organelle(Mitochondria, chloroplast)
• The ribosomes scan the messenger RNA and transfer RNA to carry out the synthesis of proteins.
• Ribosomes act similar to factories as this organelle carries out protein synthesis.

Functional characteristics of cells

All the cells of living things share the following common functions:

Nutrient uptake

A cell must uptake nutrients from the external environment through the cell membrane for cellular activities. 

Several different transport mechanisms take place in bacteria and archaea. Nutrition is the process of consuming nutrients from food and absorbing them for various functions of the cells. 

• To fight against diseases.
• For the growth and development of the body.
• For supplying the energy required for doing work.
• To restore the damaged cells and repair tissues.

Reproduction

Cellular reproduction involves cell growth and cell regeneration. It is also necessary for the growth and maintenance of the body. For example, cells are continuously growing to develop nails and hairs in humans. Cell reproduction is based on two processes. 

• Mitosis is the process of cell division generating genetically identical two daughter cells. 
• Meiosis is the process of producing four sex cells by cell division. 

Energy production

All living cells require energy to perform necessary activities for growth. This confirms that energy generation is the most significant and fundamental process of all cellular functions. Human cells can generate energy by using chemicals obtained from food as the source. 

General characteristics of plasma cells:

• Plasma cells are short-span, the activated forms of B-cells. 
• These cells can produce immunoglobulin or antibodies. 
• These cells play a major role in adaptive immunity and mainly in humoral immunity. 
• Usually, plasma cells are larger and contain more cytoplasm. 
• The cells also contain organelles such as mitochondria, lysosomes, and ribosomes. The cells are primarily involved in the generation of antibody molecules that bind to specific antigens so that they can be demolished.

Conclusion

Plasma cells are differentiated forms of B-lymphocytes that can produce immunoglobulin or antibodies. Generally, cells are the building blocks of all living organisms. They are mostly tiny and can only look through a microscope. The general characteristics of cells involve intake of nutrients, removal of waste materials, energy production, and reproduction. Plasma cells play a vital role in producing antibodies that adhere to the antigen to fight against diseases. The common characteristics of cells depend on their structure and functions. It is concluded that cells are a major important structural and functional unit of living things.