How would you explain the connection between glucose entering the body and energy created by the body to a friend, using your new biochemistry knowledge?

Glucose is a food source of energy for the body.  It is a simple sugar and once ingested, it enters the bloodstream through the digestive system and is distributed to the cells of the body.  These cells need to take in the glucose and access the energy of the molecule and use it to create the form of energy that is usable by the body- a molecule called ATP.  This molecule “traps” energy to be tapped in 3 high-energy bonds.  The “TP” stands for triphosphate:  Each phosphate bond contains a large amount of energy that can be accessed and utilized by the cell when broken and each ATP molecule contains three of these high energy bonds.

Here is a brief glimpse of the path that glucose takes in the creation of this energy housing molecule:  Once within a cell’s cytoplasm, a glucose molecule is broken down into two smaller molecules through a series of chemical reactions that yield 2 high energy ATP.  These reactions take place without molecular oxygen and, thus, are labeled as anaerobic.  This pathway, called glycolysis, is an important pathway for the body for two major reasons: First, it produces the form of molecule necessary to continue on with other energy producing pathways, and secondly, it can produce energy for the body when oxygen levels are low.  The molecules produced in glycolysis are now in a form that can enter into the mitochondria: the major site of energy production in the cell.  Within the mitochondria, the molecules enter the Citric Acid Cycle: a cyclic path of reactions that produces more ATP energy molecules as well as electron carriers.  Electron carriers are molecules that carry electrons transferred from intermediate molecules of the pathway to a final pathway called the electron transport chain.  This final pathway uses the shuffling of these electrons to the ultimate electron acceptor; oxygen; in a series of chemical reactions to pump protons across a membrane and harness the energy in many more high energy ATP bonds that can be utilized by the body. 

Important to note is that this journey that glucose takes through these energy-producing pathways is not a one-way street.  Many times the body calls for energy to be stored and this flow will stop and energy storage pathways will be utilized.  These are pathways that bind glucose molecules together and store them for times when there is a high-energy demand, like when you go for a run or engage in some other kind of exercise or hard work that calls for large amounts energy quickly.  Also important to remember is that ATP is used by the body to drive anabolic processes as well: the building up of molecules needed by the body.  Many of the chemical intermediates within the energy-producing pathways are also used in molecule building pathways.  In short, our body’s energy production, energy usage and energy storage pathways are complex and interwoven and quickly reactive to the immediate needs of the body as they change from one moment to the next.  Glucose gets pulled apart, put back together and transformed in many complex chemical reactions to meet the energy producing and energy storage demands of the body from one moment to the next.