Describe the role of energy in the body and the physiology of three named body systems in relation to energy metabolism.

Energy has many roles within the body, although many people think it is only used for muscular activity and movement. Energy is used to circulate blood, lymph and tissue fluid; breathing; taking in oxygen; making new cells; growth; repair; transmit nerve impulses; build enzymes and hormones from simple molecules. The building of complex molecules such from simple molecules is known as anabolic reactions. These reactions are all about building and storing; they help with growth and repair and store energy for future needs. The large complex molecules made during anabolic reactions are carbohydrates, proteins and lipids. The opposite of anabolic reactions is catabolic reactions these are reactions that involve breaking down complex molecules to release energy. The energy catabolic reactions make help anabolic reactions happen. As the complex molecules are broken down the waste products of the process are removed from the body through the skin, kidneys, lungs and intestines.

There are three systems which are involved in energy supply to the cells around the body; these are the cardiovascular, digestive and respiratory. Both the digestive and respiratory systems are important in the production of energy’s main ingredients, glucose and oxygen; they make energy by cellular respiration. This is the process in which the chemical bonds of energy-rich molecules are converted into energy that can be used for life processes. The digestive system is responsible for consuming food and water, using enzymes, breaking up complex molecules into simple soluble materials that are capable of passing into the neighboring capillaries of the cardiovascular system. The cardiovascular system then transports all these resources to the liver and body cells through the bloodstream, which happens because of the pumping action of the heart. As this is happening the respiratory system is persistently refreshing and reloading oxygen into the lungs, and disposing of carbon dioxide and water via the process of breathing. Dissolved oxygen passes through the lean alveolar walls in the lungs into the bloodstream and is transported to all the other cells in the body. This means that all body cells have a constant relief of glucose, oxygen and other raw materials so that the breakdown process of glucose oxidation (C6H12O6 + 6O2 → 6CO2 + 6H2O) can occur and release energy. This takes place in the cytoplasm and is completed in the mitochondria. The released energy is trapped as chemical energy in Adenosine triphosphate (ATP).