Carbon dioxide is a product of respiration resulting from the breaking of carbon-carbon bonds.
Explanation:
In respiration, which is mainly a catabolic process, there is a breakdown of carbon substrates( glucose, starch, etc) to release energy. The released energy is used to synthesise ATP, which is the energy currency of the cell with the release of carbon dioxide. Carbon dioxide which is released is obtained from the breakage of the carbon-carbon bonds between the substrates.