The sugar is chemically broken down in a process called glycolisis, that is one of the of process in the metabolic pathway.
Glycolisis: Is the metabolic pathway that converts glucose in pyruvic acid that is used by the cellular respiration to the beginning of Krebs Cycle. The free energy released in this process is used to form ATP molecules and NADH. The glycolisis have ten reaction catalyzed by enxymes and does not require oxygen.
The brake occurs in this sequence:
Glucose ---> Glucose-6-phosphate -----> Fructose-6-phosphate ------> Fructose 1,6-bisphosphate -----> Duhydroxyacetone phosphate -----> Glyceraldehyde 3-phosphate -----> 2x Glyceraldehyde 3-phosphate ------> 2x Bisphosphateglycerate -----> 2x 3-phosphoglycerate -------> 2x Phosphoglycerate ------> 2x Phosphopyruvate -------> 2x Pyruvate
Being that process the beginning of cellular respiration, that includes Glycolisis, Krebs Cycle and oxidative phosphorylation.
The general equation for the cellular respiration is:
Glucose + 6O2 ----> 6CO2 + 6H2O
The thansfer of energy occurs when carbohydrates ingested in food have they energy converted to be used by the body's cells. The carbohydrates are cleaved and the break of the molecular bonds release energy to more biochemical reactions that can produce ATP, the main energy molecule of the living organisms. The brake of ATP molecules is the main fuel for cell functioning.