Metabolism or, simply speaking, the process of breaking down ingested substances and assimilating them into the body, involves a group of chemical reactions that takes place in living organisms with a view to sustain life. The procedures enable the organisms to grow as well as reproduce, preserve their respective formation or structure and also react to the environments they survive in.
Precisely speaking, metabolism is segregated into two broad groups - anabolism and catabolism. Anabolism involves utilization of the stored up energy to create different constituents of cells, for instance, nucleic acid and proteins. On the other hand, catabolism disintegrates organic substances to garner energy in the respiration of cells.
Chemical effects involved in the metabolic procedure are categorized into several metabolic routes wherein any chemical is converted by means of a succession of phases into a different chemical by a series of enzymes. In fact, enzymes are very important in the metabolic process since they enable organisms to steer the appropriate reactions that need energy and cannot take place on their own. Thus, enzymes help in linking them to natural or instinctive reactions that emancipate energy. Since the enzymes also function as catalysts, they enable the reactions to progress rapidly as well as competently. In addition, enzymes also enable controlling the metabolic routes vis-à-vis the alterations in the environment of the cells or in receiving signals from another cell.
The metabolic process of any particular organism actually settles on the precise substances that will be nutritious or poisonous for it. For instance, a number of prokaryotes (cellular organisms without any nuclear membrane or organelles in the cytoplasm - usually bacteria and cyanobacteria) utilize hydrogen sulfide as nourishment although this gaseous substance is toxic for animals. It may be mentioned here that the metabolic rate or the pace of metabolism too has a bearing on the amount of food required by an organism for survival or to carry out its functions.
Here is an interesting thing to note. One of the remarkable aspects of the metabolic process is the close likeness of the fundamental metabolic pathways and constituents even between immensely dissimilar species of organisms. For instance, a group of carboxylic acids, which are better known as the intermediaries in the citric acid cycle that are usually found in all organisms. In fact, they are present in species as different as the single-celled bacteria Escherichia coli as well as the mammoth multi-cellular creatures, such as the elephant. Such prominent resemblances in metabolism are possibly owing to the extreme effectiveness of the pathways as well as their manifestation early on in the history of evolution.
It is a well-known fact that our bodies obtain the requisite energy from the ingested foodstuff by means of metabolism. Once we consume the food, the chemical effects in the cells of the body transform the fuel from the ingested foodstuff into energy that is required for all our actions - including physical movements, thinking as well as growth. In fact, specific proteins found naturally in the body regulate the metabolic chemical reactions and every chemical reaction is synchronized with all the activities of our body. The fact is that several thousand metabolic reactions take place in our body simultaneously. And all these metabolic reactions are controlled by our body with a view to maintain the health of the cells and keep them functional.
In effect, metabolism is a continuous process that commences when a life is conceived and it stops when the organism expires. Metabolism is imperative for all forms of life and not only for humans. The ultimate fact is that an organism dies when the metabolic process stops!
To be able to comprehend the metabolic process better, here is a simple illustration regarding the manner in which metabolism functions in humans and how it commences with plants. To begin with, the green plants absorb energy from sunlight. In the next phase, the plants utilize this energy along with the chlorophyll molecules that are responsible for the green color of the plants to create sugars from water and carbon dioxide through a process called photosynthesis (synthesizing elements with the help of light energy). Thus, when people as well as animals consume plants or plant produces they absorb this energy as different varieties of sugar together with different crucial chemicals that help in the process of cell building. The same thing applies for carnivorous animals - when they consume meat of animals that have thrived on plants, they too take in the energy accumulated by the plants. In the subsequent phase, the body breaks down or disintegrates these sugars with a view to release energy that is dispensed to different cells in the body. In turn, these cells use the energy as fuel for carrying out their normal functions.
Once a food has been consumed, it travels to the digestive system where molecules known as enzymes break down carbohydrates into simple forms of sugar, such as glucose, proteins into amino acids and fats into fatty acids. While sugar remains the most efficient form of energy, the body is also able to use amino acids and fats for supply of energy whenever the need arises. All these compounds that have the potential to generate energy are eventually soaked up into the blood stream and are transported to the different cells in the body for the normal functioning.
When these compounds (glucose, amino acid and fat) enter the cells, other enzymes work to accelerate or control the chemical effects concerned with the metabolizing these compounds. Energy is released during the metabolizing of these compounds and this energy may be used up by the body for carrying out some immediate function, or stored up in the body tissues, particularly the muscles, liver and body fat for use when necessary.
In this manner, the metabolic process may certainly be described as a genuinely balancing act concerning two different types of actions that continue simultaneously. While one action - anabolism, helps in reinforcing the body tissues and stores up energy, the other action - catabolism, helps in breaking down the body tissues and storing up energy with a view to produce more energy for the body to carry out all its normal functions. A brief discussion on these two dissimilar, but concurrent processes of metabolism - anabolism and catabolism, are presented below for a better understanding of the subject.
Nevertheless, the above mentioned dissimilar types of metabolism is based on redox (a chemical reaction between two substances in which one substance is oxidized and the other reduced) effects that entail transmission of electron from the reduced contributor molecules like water, organic molecules, hydrogen sulfide, ammonia or ferrous ions to acceptor molecules like nitrate, oxygen or sulfate. In animals, such reactions entail disintegration or breaking down of compound organic molecules into simpler molecules like water and carbon dioxide. However, in organisms that have an aptitude for photosynthesis, for instance, plants and cyanobacteria, the reactions involving transfer of electrons do not discharge any energy. On the contrary, the reactions are utilized as a manner to store up energy taken in from sunlight altering small molecules into bigger ones that are more complex in nature. Examples of such molecules include molecules of carbohydrates, fat and protein.
Metabolism is a complex chemical procedure and, hence, it is hardly amazing that several people consider metabolism of it in its basic sagacity. According to them metabolism is a process that has some bearing on the manner our body adds or loses weight. And when people talk of weight gain or loss, they actually refer to the calories taken in by our body. Precisely speaking, calorie denotes the element that determines the amount of energy provided by any food. For instance, compared to an apple, a chocolate bar provides more calories to the body and this may occasionally be a good thing. Similar to an automobile that stores up fuel in the gas tank till the time it is required to fire the engine, our body also stores up calories, basically in the form of fat for use when necessary. Here is a simple example. In case you fill in excess fuel in the vehicle's tank, it will overflow on the road. Similarly, when an individual consumes calories in excess, they will 'run over' in the form of surplus body fat.
Several aspects influences the number of calories burnt or used up by an individual. These factors include the quantity of fat and muscle the individual has in his or her body, the relative extent of workouts undertaken by the individual as well as his or her basal metabolic rate (BMR). BMR is actually a evaluation of the pace at which an individual's body 'burns' or uses up energy in terms of calories while in a resting position. In fact, the BMR has the aptitude to play a significant part in an individual's inclination to gain weight. For instance, an individual with a low BMR actually burns very little number of calories while he or she is at rest or sleeping. Interestingly, compared to same sized people having an average BMR and eating the same type of food and undertaking similar amount of exercises, persons with low BMR will accumulate more body fat over a period of time.
Broadly speaking, any ailment of the metabolic rate is a disease that originates from any anomalous chemical effect in the cells of an individual's body. In fact, majority of the metabolic disorders entail anomalous intensity of enzymes or hormones or else the working of those enzymes and hormones. If the metabolic rate of the chemicals in the body is flawed or obstructed, it may result in the accumulation of venomous substances in the body. Alternately, such a situation may also lead to a deficit of the substances essential for the regular functioning of the body. What is important is that any of these conditions may result in grave symptoms.
It may be mentioned here that a number of ailments related to metabolism are inheritable. In other words, such conditions are referred to as inherent flaws or inborn errors of metabolism. Therefore, soon after the birth of a baby, he or she is subjected to several examinations called newborn screening test to find out if they are enduring any such metabolic malady. Several such inherent flaws of metabolic rate may possibly result to grave problems. Often they may even be the cause of death of a baby unless these conditions are restricted or regulated by means of proper diet and/ or drugs from a very early stage.
Some instances of metabolic diseases and conditions are briefly discussed below.