Catabolism

Catabolism is the breakdown of biological and chemical polymers and the release of energy within the body. The process explains the production of monomers, or molecules that can chemically connect with other molecules to produce a long-chained complex called a polymer, that helps energize the body from the cellular and muscular levels and the body’s holistic physical activities and movements. Anabolic reactions, or the reactions used to produce polymers and considered the opposite of catabolism, uses the energy gathered in adenosine triphosphate (ATP) as fuel. Anabolic reactions are closely related to catabolic reactions, given that catabolism is required in the production of ATP energy. Anabolic reactions consume this ATP-released energy to manufacture hormones, enzymes, sugars, and other substances required for cell growth, reproduction, and tissue repair. The overproduction of energy through catabolic reactions results in excess energy that the body stores as fat or glycogen. Fat tissue is largely dormant, unlike muscle or organ tissue. The maintenance of fat cells is relatively low compared to other biological and chemical cells in the body, given its comparative sedentariness.

Background

Catabolism allows the breakdown of polymers—polysaccharides, nucleic acids, and proteins—into their respective monomer forms. Polysaccharides, otherwise called complex carbohydrates, disintegrate into monosaccharides, also called simple carbohydrates. Starch, glycogen, and cellulose are considered complex carbohydrates; glucose, ribose, and fructose are considered simple carbohydrates. Nucleotides are the monomers that form nucleic acid polymers. Nucleic acids are biological molecules that carry genetic information that defines the basis of each individual’s hereditary lineage. Ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) are nucleic acids that, when broken down, form purine, pyrimidine, and pentose nucleotides. These nucleotides control and aid in the allocation of the body’s energy. On the other hand, the breakdown of proteins introduces amino acids. Amino acid monomers from the catabolic lysis of proteins can either be directly recycled to produce more amino acids or can be rehabilitated in the production of other compounds. An example of protein catabolism is glucose, an essential amino acid that is present in the blood.

The decomposition of organic nutrients stored within ATP molecules is essential in the release of energy. The breakdown of these organic nutrients produces catabolic hormones, such as cortisol, glucagon, adrenalin, and cytokines. Cortisol, the stress hormone, reacts when the body senses stress and anxiety. Cortisol is generated by a section of the adrenal gland called the adrenal cortex. The adrenal glands are situated in the endocrine system and are responsible for the production of a variety of hormones. On the other hand, glucagon is a catabolic hormone that consists of alpha cells in the pancreas. Glucagon initiates the liver to collapse glycogen to enhance and raise blood sugar levels. Glycogen is a carbohydrate found in the liver and is a primary source of energy. The catabolism of the hormone glucagon signals and instructs the liver to break down glycogen, thus allowing the carbohydrate to enter the blood stream as sugar and serve as fuel for the body’s energy.

Adrenalin, also known as epinephrine, is a hormone constructed by the adrenal medulla oblongata in the adrenal. The medulla is situated in the center of the adrenal gland and aids in alleviating and comprehending a person’s emotional and physical stress. Adrenalin increases the body’s heartbeat, boosts and strengthens the heart’s contractions, and expands the lung’s bronchioles. Adrenalin is one of the primary hormones that affects humans’ and animals’ response to fear; this hormone assists in choosing the proper response: whether to go forth or retreat. The catabolic hormone cytokine is a small protein that affects the cellular interaction, mainly with regard to communication and behavior. Interleukins and lymphokines are examples of cytokines that the body releases as an immune system response.

Topic Today

Metabolism, mainly catabolism and anabolism, are closely related to the maintenance of a body’s weight and physical abilities. Body weight is the difference between catabolism and anabolism, or, in other words, catabolism minus anabolism. Body weight considers the energy the body releases (catabolism) minus the energy the body consumes (anabolism). As was previously stated, excess energy from catabolic and anabolic reactions is stored as fat or glycogen. These fat tissues are stored mainly as carbohydrates in the liver and muscles. One gram of fat produces nine calories (kcal), while a gram of protein or of carbohydrate produces four calories.

It is easy to presume an overweight body has surplus energy as a result of catabolic and anabolic reactions; however, the other hormonal problems may also be present. In addition, excess weight may also be the result of a principal medical condition, such as hypothyroidism, that affects the lack of consumption or overproduction of energy. Common belief is that slimmer people have higher metabolisms, while obese and overweight people have lower metabolisms. Hypothyroidism is a medical condition where the thyroid glands lack the activity required to continuously produce the thyroid hormone thyroxine. Thyroid hormones control and regulate the body’s catabolic and anabolic reactions, and a lack of thyroxine slows the body’s physical abilities to properly catabolize and anabolize energy, thus increasing the fat tissue from excess energy present.

Weight gain and the surplus of fat cells may be correlated to an energy imbalance. A proper medical evaluation is necessary in determining the true cause of weight gain, be it a medical condition or energy imbalance. Although basal metabolism, or the metabolic rate at which we operate while at rest, cannot be changed considerably, other long-term options can significantly affect the body’s metabolic rate, such as accumulating and increasing the body’s muscle mass. It is difficult to generalize the calorie requirements required to maintain a healthy body, given that a person’s specific metabolic rate is based on their body size, body composition, age, and gender. Larger body masses require more calorie consumption compared to those with lower body masses. However, it is important to distinguish that those with more muscle mass than fat do require more calorie intake. Higher muscle-to-fat ratios generally have higher metabolic rates than those who have lower muscle-to-fat ratios, even at the same weight.

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