Four Major Organic Polymers
Cells can be considered as the basic unit of an organism composed of carbon-containing molecules, water, and inorganic ions. Fundamentally, the interaction between cell constituents and water plays a central role in biological chemistry. Additionally, interactions of polar and non-polar molecules with each other as well as with water are vital in the establishment of biological structures such as the cell membranes. Water is a polar molecule with both slight positive and negative charges on the hydrogen and oxygen atoms respectively and account for 70% of the total cell mass. Nevertheless, organic molecules constitute the unique elements of cells. The majority of the organic compounds may be classified as carbohydrates, proteins, lipids, and nucleic acids. Carbohydrates, proteins, and nucleic acids are macromolecules formed by the joining of monomers through the process called polymerization. Together with lipids, the four mentioned macromolecules constitute the core chemistry of cells regarding functions and structure, hence, referred to as the four major organic polymers. This essay presents a detailed discussion of these four organic polymers with a focus on nomenclature, chemical makeup, function, and location.
Simple sugars such as glucose and polysaccharides are named carbohydrates. In turn, carbohydrates are scientifically referred to as saccharides, which is a complex nomenclature. Saccharides are primarily located on the surface of the eukaryotic cell membranes. In addition to being the major cells nutrients, carbohydrate breakdown provides energy and basic material for the synthesis of other organic polymers. The polysaccharides then form the building blocks of cells in the form of sugars. Moreover, the sugar polymers act as cell recognition process markers in protein transportation as well as in the adhesion of one cell to another.
Moreover, monosaccharides, which are the representatives of simple sugars, consist of joined carbon, hydrogen, and oxygen atoms. The dehydration reactions bring together several monosaccharides which are linked by glycosidic bonds forming either oligosaccharide or polysaccharide polymers depending on the number of simple sugars involved in the reaction. Glycogen and starch constitute the two common polysaccharides in animals and plants cells respectively. Starch and glycogen primary functions include glucose storage which explains their structural similarities. In addition to cell structure and energy storage roles, carbohydrate polymers help in protein transportation and cell recognition which is critical in the interaction of cells in multicellular organisms.
Lipids, also scientifically known as Fatty acids, are located on the cell membrane, which defines their various functions. Lipids are known to play three major roles in cells: they store energy; take part in the formation of cell membranes, and contribute to cell signaling as both messenger molecules and steroid hormones. Fatty acids consist of long chains of hydrocarbons and are the simplest forms of lipids. They can be either saturated or unsaturated and contain non-polar carbon-hydrogen bonds that are unable to interact with water. These hydrophilic characteristics of fatty acids play a significant role in the behavior of complex lipids that contribute to the formation of biological membranes. Fatty acids become linked to glycerol to form fats and triacylglycerols for the purpose of storage. Fats yield more than twice their energy per weight in comparison to carbohydrates, hence producing a more efficient form of energy storage. In addition to phospholipids, cell membranes also contain cholesterol and glycolipids that function as signaling molecules between and within cells.
Nucleic acids, also scientifically referred to as Deoxyribonucleic acids (DNA) and Ribonucleic acids (RNA), form the principal informational molecules of a cell. DNA contains genetic material primarily located in the nucleus. Conversely, RNA participates in several cellular activities such as relaying information from the DNA to ribosomes through mRNA. There are two types of RNA, namely ribosomal RNA and transfer RNA, which contribute to protein synthesis. In addition to informational and transport functions, RNA act as a catalyst in RNA processing and protein synthesis reactions. Nucleotides are the basic units of RNA and DNA polymers consisting of pyrimidine and purine bases joined to phosphorylated sugars. Phosphodiester bonds are formed in the polymerization of nucleotides to form nucleic acids. Polynucleotides makeup cellular DNA and RNA and contain millions of nucleotides. Besides being nucleic acid building blocks, nucleotides play a critical role in cell processes such as generation of chemical energy and communication within cells.
The primary responsibility of proteins involves execution of genetic information conveyed by nucleic acids. Scientifically known as peptides, proteins are not limited to one location in a cell since they are involved in the formation of every part of the cell structure. Interestingly, proteins are the most diverse polymers, each containing thousands of different polypeptides. These polymers perform several functions: the formation of the structural components of cells and tissues; the transportation and storage of small molecules such as oxygen; the informational transmission between cells through hormones and antibody protection against infection. The proteins’ ability to act as enzymes is one of their most fundamental properties. It enables the proteins to catalyze almost all the chemical reactions in the biological systems. This explains the proteins central importance in organic chemistry considering the fact that they direct virtually all the cellular activities. Moreover, proteins consist of different amino acids whose side chains determine the structure and the function of each polymer. Peptide bonds form chains of amino acids known as polypeptides. The sequence of the amino acids in a polypeptide defines the characteristic of protein with each consisting of unique amino acid sequences. Consequently, the twenty different amino acids lead to the variation in the formation of proteins which explain the complexity and diversity of this group of macromolecules and their suitability to the extensive variety of tasks that they perform in cell biology.
To summarize, biological polymers may be viewed as large molecules formed as a result of many similar monomers linked together. The function, location and characteristics of the four organic polymers mainly depend on the number of molecules joined which also influence their duties in a cell. In addition, monomer arrangement and sequence contribute towards molecular uniqueness and diversity from one species to the next as well as from cell to cell in the same organism.