Your body gets energy from food through metabolism. The process of metabolism involves a chain of biochemical reactions that occur in all organs and cells. These reactions convert nutrients from food into energy needed to maintain life.
Function
Metabolism in the body occurs at all levels, ranging from cells and tissues to organs. Metabolism helps your body to obtain energy from food and to store energy for later use. The main organs in the body that regulate metabolism are the digestive system, the liver, the pancreas, the circulatory system and the kidneys. Their roles in metabolism are:
Food first goes through the digestive system, which processes and absorbs the nutrients. The organs in the digestive system are
mouth, esophagus, stomach, large and small intestines, rectum and anus. Absorbed nutrients are sent to the liver, which is one of the body's most active metabolic organs. The liver packages the nutrients, and transports them to other organs. The liver also stores vitamins and minerals, and is responsible for detoxifying alcohol and drugs. The pancreas produces insulin and other hormones to regulate the body's use of glucose, an important source of energy. The heart and blood vessels deliver blood, oxygen and nutrients to all cells and carry wastes and carbon dioxide away from the cells. The kidney maintains the blood's delicate chemical balances by processing waste products from the blood and reabsorbing nutrients.
Types
Metabolism is often classified into anabolism and catabolism. Anabolism is reactions in which small molecules are put together to build large ones, for instance glucose units are strung together to make glycogen chains, glycerol and fatty acids are assembled into triglycerides, and amino acids are linked together to make proteins. Anabolic reactions consume energy.
While anabolism involves building up, catabolism involves decomposition. During catabolism, large molecules are broken down to smaller ones. Catabolic reactions usually release energy.
Considerations
The energy demand of an individual depends on his metabolism, characterized by his basal metabolic rate, and how active he is. Basal metabolic rate is the energy consumption rate of the body at rest. Basal metabolic rate is different for each person and depends strongly on his or her physiology, age, gender and genetics. Even for an individual, the basal metabolic rate may vary under different circumstances. For instance, your basal metabolic rate tends to be higher if you are under stress. Basal metabolic rates are higher in physically active people, children and pregnant women. As people get older, their basal metabolic rate decreases.
Knowing one's rate of metabolism is important in figuring out the right energy balance.
Significance
If we understand how metabolism works, we can learn to manage our energy balance better. This includes managing the energy intake from food and the energy expenditure from exercise or physical work. If we eat more than our bodies need, extra nutrients are building up and stored in fat cells. The fat cells will stay expanded and eventually lead to obesity, which is a major risk factor for cardiovascular diseases, cancers and diabetes.
History
The word "metabolism" means "change" in Greek. Studies of metabolism can be traced back to the 13th century. One of the earliest studies on metabolism was published in the 16th century by Santorio, in which he examined how his body weight changed with different activities including sleep, sex, eating and exercise. In the early 19th century, Louis Pasteur and Friedrich Wöhler showed that chemical reactions in cells are similar to reactions in chemistry. One century later, Eduard Buchner was able to separate enzymes for the first time. This marked the birth of modern biochemistry. Modern technologies, like chromatography, and X-ray diffraction, lead to new discoveries in metabolic pathways. Now, we have a fairly complete picture of how different components of the metabolic pathways in different organs of the body interact with each other. This lays the foundations for a large number of drugs that target metabolic diseases.
Tags: metabolic rate, from food, basal metabolic rate, digestive system, Basal metabolic, basal metabolic, Basal metabolic rate