Carbohydrates are sugars and sugar derivatives whose formulas can be written in the general form: Cx(H2O)y. (The subscripts x and y are whole numbers.) Some typical carbohydrates are sucrose (ordinary cane sugar), C12H22O11; glucose (dextrose), C6H12O6; fructose (fruit sugar), C6H12O6; and ribose, C5H10O5.Since the atomThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume. ratio H/O is 2/1 in each formula, these compounds were originally thought to be hydrates of carbon, hence their general name.
Glucose, by far the most-common simple sugar, is a primary source of energyA system's capacity to do work. for both animals and plants. Because they contain free glucose molecules, dextrose tablets or foods such as grapes and honey can provide a noticeable “lift” for persons tired by physical exertion. The individual glucose molecules pass rapidly into the bloodstream when such foods are eaten. Glucose is also the monomerOne of the units that joins with other units to form a polymer. from which the polymers cellulose and starch are built up. The structural material of plants, from the woody parts of trees to the cell walls of most algae, is cellulose. Plants store energy in starch, providing a source of glucose for all but the simplest organisms. The energy in starchy foods is not as rapidly available, however, since the polymeric structure must be broken down before glucose is released. As a consequence of the ubiquity of starch and especially cellulose, carbohydrates are by far the most plentiful organicRefers to the branch of chemistry that studies compounds containing carbon, usually in combination with hydrogen and other elements such as O, N, S, and P. Certain small ions and compounds containing carbon (such as carbonate ions and carbon dioxide) are not considered to be organic, but rather are classed as inorganic. compounds in the biosphere.