1.What is Metabolism?

Material metabolism and energy metabolism are both parts of metabolism. Energy metabolism is the interconnected and coupled exchange of energy between the organism and the external environment as well as the transformation of energy within the organism, whereas material metabolism refers to the exchange of substances between the organism and the external environment and the transformation of substances within the organism. For instance, when there is an excessive energy intake after eating, fat synthesis increases, and during hunger, fat mobilization occurs, freeing energy for utilization by the organism.


1) Metabolism of substances

The metabolic changes of all substances in living beings are collectively known as substance metabolism, which encompasses anabolism and catabolism. In living organisms, the synthesis of new chemicals and the breakdown of old substances occur simultaneously. Catabolism refers to the breakdown of all substances in an organism, which belongs to the category of dissimilation, such as the complete breakdown of sugars into carbon dioxide and water through the tricarboxylic acid cycle. Anabolism refers to the synthesis of all substances in an organism, which belongs to the category of assimilation, such as the synthesis of proteins from amino acids and nucleotides from nucleic acids.


2) Metabolism of energy

①Changes in energy metabolism

Energy metabolism is the process of exchanging chemicals for energy. The external environment provides the body with nutrition for anabolic processes as well as energy, primarily from the chemical energy found in the nutrients. The organism releases the chemical energy needed for living activities when these nutrients are catabolized. Aside from the synthesis of other parts of the body, the chemical energy is employed for a range of living processes. But not all chemical energy can be transformed into usable energy; part of it must unavoidably be released as heat, or heat of emission (q).Free energy (F) and heat of reaction (H) are two terms used to describe the total amount of energy converted. The law of conservation of energy states that the heat of reaction equals the free energy of transformation plus the heat of emission, or H = F + q.

②Basal metabolism

The smallest quantity of energy needed by all body organs to maintain life is known as basal metabolism. When the body is awake and extremely quiet, unaffected by muscle activity, the environment's temperature, food, or mental stress, it is the minimal energy metabolism necessary to maintain essential critical functions like breathing and heartbeat. The amount of heat [kJ/(h-m)] per square meter of body surface area per hour, also known as the basal metabolic rate, can be stated to compare the energy metabolism rates of various persons. The basal metabolic rate varies according to gender and age, and is higher on average in men than in women; it is higher on average in young children than in adults; and it decreases with age.

The basal metabolism of a normal person is about 5900~7500kJ per day.

③Respiratory quotient and caloric value of foods

a. Respiratory quotient

The respiratory quotient, which measures the amount of oxygen consumed and carbon dioxide exhaled, is necessary for the organism to oxidize nutrition. An essential metabolic idea is the respiratory quotient. Depending on the structure and chemistry of the material, as well as the proportion of carbon to hydrogen and oxygen, each nutrient has a unique respiratory quotient. While the average respiratory quotient of a typical person's varied diet is 0.85, the respiratory quotients of sugar, protein, and fat are each 1.0, 0.8, and 0.7, respectively. It is possible to quantify the respiratory quotient to forecast energy expenditure in various physiological and pathological conditions.

b. Caloric value of foods

The three energy-producing substances carbohydrates, lipids, and proteins—found in both animal and plant foods—provide the body with the energy it needs to function. The "calorific value of food" or "caloric value of food," also known as the "energy factor," is the amount of energy created per gram of an energy-producing ingredient oxidized in the body. The calorific value of food is frequently used in metabolic research to gauge the food's ability to provide energy. The calorific content of sugar, fat, and protein is 4kcal, 9kcal, and 4kcal per gram, respectively. This translates to 17kJ, 38kJ, and 17kJ per gram, respectively, in the current international unit of calorie computation.



An organism can regenerate itself through metabolism, which is the continuous exchange of matter and energy between the organism and the outside environment as well as the continuous transformation of matter and energy within the organism. Life expires if metabolism stops.

Matter metabolism and energy metabolism are the two components of metabolism. The exchange of substances between an organism and its external environment as well as the transformation of those substances within the organism are referred to as metabolism of substances.

 Similarly, the exchange of energy between an organism and its external environment as well as the transformation of that energy within the organism are referred to as metabolism of energy.The process by which an organism converts the nutrients it absorbs from the outside world into its own constituent substances and stores energy is known as assimilation, sometimes known as anabolism. The process by which an organism breaks down a portion of its own components, releasing the energy contained therein and eliminating the byproducts of decomposition from the body, is known as anabolism, sometimes known as catabolism.





1 Taking in nutrients from the environment.

2: Changing the externally supplied nutrients into the structural building blocks that the body needs on its own, i.e. the macromolecules' individual precursors.

3 Creating their own macromolecules, like as proteins, nucleic acids, lipids, etc., by putting structural components together.

4. The breakdown of organic nutrients.

5 – Supply all the energy required for daily tasks


4.Fat in metabolism

Fats are concentrated energy sources. They provide twice as much energy per unit of weight as either protein or carbs.

Assisting in the creation of cellular structure, forming an insulating and cushioning layer around vital organs, facilitating the absorption of fat-soluble vitamins, and serving as an energy reserve are just a few of the many functions that fats do.

Essential fatty acids include unsaturated fatty acids like linoleic, linolenic, and arachidonic acids. You must incorporate these into your diet. Saturated fats and cholesterol have been linked to both arteriosclerosis and heart disease.

5.Metabolism factors

 Although the condition of the metabolic process is dependent on a number of important aspects, it is nevertheless quite complex. The metabolic process may be slightly impacted by certain meals you consume. Your present weight and body size also have an impact. Your metabolic rate might be impacted by a few, uncommon health issues and illnesses.

A decrease in metabolic rate has been associated with polycystic ovarian syndrome in females. Endocrine conditions including hypothyroidism and problems of the pituitary gland, which can all slow the metabolism and make it more difficult to lose weight, can also affect both men and women.

Your body's size and composition have a significant impact on your metabolism. Even when at rest, a person with more muscular mass or a larger body will burn more calories just by existing. Because the body tends to lose some muscle mass as we age, your age is also a very important aspect.

Your metabolic rate decreases as a result of some of that muscle being replaced by fat in your overall body weight. Men typically burn more calories than women because they are biologically more muscular and have less body fat. Lack of sleep, rapid weight loss, and failing to consume enough calories to maintain bodily functioning can all affect your metabolism and energy levels.

Your resting metabolic rate is largely out of your control, but you can burn more calories by engaging in frequent physical exercise. Since muscle tissue consumes more energy than fat tissue, those with larger muscle mass can also burn calories more quickly.


6.How to increase metabolism

1. Take more exercise. Your cardio workout will burn more calories in less time if you use interval training. Take a minute to sprint, followed by two minutes of walking. For 20 or 30 minutes, repeat this procedure.

2. Do weightlifting. You can burn more calories when at rest if you increase your body's muscular mass. Choose a strength-training program that targets your entire body.

3. Never miss a meal, especially breakfast. As you digest meals, calories are really burned, therefore it's important to keep the furnace going.

4. Consume food that burns fat. Protein, hot peppers, and green tea are among the foods that have been shown to increase metabolism. At every meal, include some of these foods, particularly protein. Protein is particularly crucial since it requires more energy to digest than other diets and aids in the development of lean muscular tissue that burns fat.

5. Get a good night’s sleep every night. Studies have shown that lack of sleep affects activity in the brain’s frontal lobe, which may decrease your impulse control and decision-making ability.


7.Metabolic pathways

Metabolic pathways are hierarchical groups of the chemical reactions that make up metabolism. These enable a set of enzymes to convert the fundamental chemicals from nutrition through a series of stages into a different chemical.

Because they enable organisms to drive energy-intensive desired reactions, enzymes are essential to metabolism. Along with those that release energy, these reactions also occur together. Enzymes facilitate these reactions by acting as catalysts, allowing them to happen fast and effectively. In reaction to alterations in the cell's environment or signals from other cells, enzymes also enable the regulation of metabolic pathways.

Previous: Cytobiology