It is a scientific fact that all living things, from the largest mammal, the blue whale, to the microscopic Paramecium, are made up of cells. These cells are, in turn, made up of different chemical compounds that fulfill a myriad of purposes in a living organism. Scientists have grouped these organic compounds into four different kinds: carbohydrates, lipids, proteins and nucleic acids. They are called organic compounds because they were first taken from living organisms, and they are readily identifiable by the general presence of carbon molecules within their structure. Each kind of compound is once again sub divisible into different types, to further increase the specificity of their functions.
The first type, carbohydrates, is composed of compounds that are either sugars or starches, and are made up of the elements carbon, hydrogen and oxygen. Sugars are made up of simpler single rings of Carbon. These single rings are called monomers, and the addition of another monomer elevates the physical status of the sugar to a dimer, followed by a polymer. The number of rings that are observable in a sugar also determines the type of sugar it is; sugars can be typed as monosaccharides, disaccharides and polysaccharides, and these divisions are based on the number of sugar monomers that are present in a carbohydrate compound. Polysaccharides, such as glycogen and starch, are used as excess sugar-storing compounds in animals and plants respectively. These methods of storing sugars are very important to living systems because carbohydrates are used as readily available energy sources by animals and plants in times of necessity. Carbohydrates are also very important for their structural properties, such as in the cellulose of plants, and the chitinous coverings of arthropods.
The organic compound group known as lipids are made up of those substances such as fats, waxes and oils, as well as steroids. The elements, which they are made of, also include carbon, hydrogen and oxygen, and some examples of lipids contain phosphorous. Unlike carbohydrates, lipids are usually insoluble in water. Lipid fats are used as insulation and energy storage by living organisms. Steroids are multi-ringed lipids, and examples of these perform very specialized functions, such as hormones and their ability to perform as chemical messengers throughout an organism. Phospholipids and waxes are both important structural lipids; the former is integral in the formation of cellular membranes, while the latter is a type of organic waterproofing employed by animals and plants.
Proteins, like carbohydrates and lipids, are also made up of carbon, hydrogen and oxygen. However, there are other elements, such as nitrogen and sulfur, which are integrated into proteins. Nitrogen is found in all amino acids, the basic unit of a protein, while sulfur is only found in some of them such as methionine and cysteine, and there are around twenty amino acids in the alphabet that makes up whole proteins. Amino acids are linked together by peptide bonds, and a long series of such bonded amino acids are called polypeptide chains. The sequence of amino acids is a polypeptide chain, as well as the way a finished protein is folded, is crucial to the ability of this compound to fulfill its functions in a living organism. These functions are manifold and occur in every level of an organisms’ structure: from the facilitation of transport across cellular membranes to the interaction of actin and myosin proteins in muscles that allows for movement.
The third type, nucleic acids, is the organic compound responsible for the passing on of hereditary information. They are composed of a five-carbon sugar known as ribose, a nitrogenous base and a phosphate group. There are two types of nucleic acid: deoxyribonucleic acid, more commonly known as DNA, and ribonucleic acid, or RNA. There are two main differences between them, the first being the sugar ring can either be ribose or deoxyribose, and the second the composition of their nitrogenous bases; DNA has the paired bases guanine and cytosine, and thymine and adenine, while in RNA, uracil is the nitrogenous base paired with adenine.
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