Carbon is an element and the definition of an element is that it cannot be broken down into any other element using chemical means.
through fusion and fission it could be broken down or built up into oxygen or nitrogen or any number of other elements. But not without unearthly large amounts of energy (usually from a supercollider)
When citric acid breaks down, it releases carbon dioxide gas, water, and energy.
A complex substance breaking down into two or more simpler substances is typically a decomposition reaction. In these reactions, one reactant breaks apart into multiple products through various processes, such as heat, light, or the presence of a catalyst.
carbon
One substance that the body stores energy as is glycogen, which is a complex carbohydrate stored in the liver and muscles. When needed, glycogen can be broken down into glucose for energy.
An element is a substance that chemical reactions cannot break down into simpler substances. Elements are made up of only one type of atom and cannot be further broken down by chemical means. Examples of elements include gold, oxygen, and carbon.
an electron
An element.
Some reactions are possible:2 CO2 = 2 CO + O2CO2 + 2 Mg = 2MgO + C
Carbon into carbon monoxide and carbon dioxide
This is the atom of a chemical element (of course by chemical methods).
decomposition
Biccarbonate is a oure substance because it is not part of a mixture, it is an ion. If you cannot break down a solution without the help of a chemical reaction (ex. Chromate CrO4 cannot be broken down further without a chemical reaction) then it is a pure substance.
Carbon is an example of an element, which is a pure substance that cannot be broken down into simpler substances by chemical means.
Carbon monoxide is considered a pure substance because it is a compound composed of two elements, carbon and oxygen, in a fixed ratio (1:1). It cannot be separated into simpler substances by physical methods.
Ordinary table sugar is a complex hydrocarbon molecule: C12,H22,O11. Notice that it's 11 water molecules and 12 carbon atoms. When Sugar is heated, some of the water is driven off leaving extra carbon atoms laying around. And what color is carbon? Making sugar is a relatively complex process, breaking it down just takes heat.
Some are broken down into less complex carbon chains eventually turned into glucose or another energy source. Some contain glycerol which is also broken down by the body.
The substance that returns to the air through the process of cellular respiration is carbon dioxide. In cellular respiration, glucose is broken down to produce energy, carbon dioxide, and water. The carbon dioxide produced is released into the air when we exhale.