METABOLISM

Metabolic reactions are organized in a series of pathways. for each pathway, there is a starting molecule which is modified in a series of biochemical reactions, which then produce intermediates that can produce a final product or products metabolic reactions require an adequate amount of oxygen and nutrients in order to be maintained. The 

Oxygen can be obtained from both, the air we breathe in, and in small amount from ingested raw fruit and vegetables. Nutrients, including carbohydrates, lipids, proteins, and water, are obtained from our consumed food and drink. In conclusion, the diet has an essential role in metabolism.

Water is the nutrient we need most, and we can find it in our both consumed food and drinks.it does many functions in the body, but being the medium in which many metabolic reactions happen is its most important one.

Once the nutrients are digested by enzymes and absorbed in the gastrointestinal tract, the products can then be used to produce energy, which is either used to create more complex structural and functional molecules or can be saved as an energy source for further usage. Metabolic processes have a lot of functions in the body, including:

1. Growth and cell division: the many processes that are necessary for growth, such as DNA replication and mitosis, are fueled by the energy produced during cellular metabolism.

2. Cellular and organismal processes: many cellular functions depend on the energy generated by metabolic processes, such as secretion, contraction, the formation and propagation of action potentials, and the build of complex molecules. Moreover, the energy generated by metabolic processes motive the maintenance and repair of the body.

Nutrition is the process of providing or obtaining the food required to preserve health and growth of the body. This process happens by the existence of nutrients, which are chemical substances that we get from the digestion and absorption of the food.

Nutrients have three main functions: first, providing energy for boosting the reactions in our bodies, second, they have a role in adjusting body processes, finally, they aid in the maintenance of cells and tissues.
the source of the nutrients used in these functions can either be generated in the body itself, or it can be extracted from the food in the diet we eat, these types of nutrients are therefor called essential nutrients as the body is unable to make it itself.
 

There are six main groups of nutrients: water, carbohydrates, lipids, proteins, minerals, and vitamins.

Water, carbohydrates, lipids, and proteins are known as macronutrients because the body requires them in large quantities. 

Minerals and vitamins are known as micronutrients because the body needs them in smaller amount. 

Insufficient and excess intakes of nutrients can both lead to a number of health issues.
 

ِAll the six groups play a role in the regulation of body processes, maintenance, and repair of the cells and tissues. However, out of these six groups, only carbohydrates, lipids, and proteins do provide the body with energy, with Carbohydrates having the maximum proportion of an average diet, and that is because of two reasons, first is due to the glucose being the number one source of energy in the body, and second the tendency that some cells have towards Glucose as it is their only source of energy.

Nutrition is the process of providing or obtaining the food required to preserve health and growth of the body. This process happens by the existence of nutrients, which are chemical substances that we get from the digestion and absorption of the food.

Nutrients have three main functions: first, providing energy for boosting the reactions in our bodies, second, they have a role in adjusting body processes, finally, they aid in the maintenance of cells and tissues.
the source of the nutrients used in these functions can either be generated in the body itself, or it can be extracted from the food in the diet we eat, these types of nutrients are therefor called essential nutrients as the body is unable to make it itself.
 

There are six main groups of nutrients: water, carbohydrates, lipids, proteins, minerals, and vitamins.

Water, carbohydrates, lipids, and proteins are known as macronutrients because the body requires them in large quantities. 

Minerals and vitamins are known as micronutrients because the body needs them in smaller amount. 

Insufficient and excess intakes of nutrients can both lead to a number of health issues.
 

ِAll the six groups play a role in the regulation of body processes, maintenance, and repair of the cells and tissues. However, out of these six groups, only carbohydrates, lipids, and proteins do provide the body with energy, with Carbohydrates having the maximum proportion of an average diet, and that is because of two reasons, first is due to the glucose being the number one source of energy in the body, and second the tendency that some cells have towards Glucose as it is their only source of energy.

Food calories or also known as kilocalories, or Calories (capital C) are the typical measurements for the nutrients contained in the daily food, The amount of nutrients obtained from food on a daily basis can be measured in food Calories, it differs depending on the type of the nutrients, for example, both carbohydrates and lipids produce four Calories per one gram, on the other hand, lipids can produce nine Calories per 1 gram.

Guidelines recommendations for the medium intake of Calories per day are nearly 2000 Calories for adult women and 2500 for adult men. However, these numbers can vary depending on the sex, age, weight, and activity levels.

When the diet contains more Calories than the body needs, the extra nutrients can be stored and used later when needed, on the other hand, when the diet contains less Calories than the body needs, the nutrients are not enough to fulfil the energy required, so that the body has to use the stored nutrients as an energy source.

The diet should not only contain the adequate range of Calories number, but it also must have a wide variety of nutrients, which is not always reachable even if the diet contains the right amount of Calories, for that to be achieved, the diet must be varied, and balanced, with a sufficient, not excessive, number of Calories, and it had better include all six groups of nutrients, a sufficient and varied diet would include food from all the major food groups, from grains, vegetables, and fruits to meat, fish and dairy products.

As Water being the essential component of the body, it has a major role in delivering necessary nutrients in the body, transporting metabolic waste, assisting many reactions in the body, and aiding in maintenance of the temperature of the body.

About 60% of the body is made up of water. As a result, water is needed more than any other nutrient to keep this aqueous environment.

Water is obtained mainly from fluids and eating moist food, it can also be a product of certain metabolic reactions, as in aerobic cellular respiration where it is produced in the electron transport chain. 

As for extraction, the kidney is responsible for the largest amount through filtration and then urine formation. There are also other ways, as through perspiration through the skin, and exhalation of air through the lungs.

There must be a balanced intake and output of water, in order to maintain hemostasis, which is preserved by many mechanisms as the perception of thirst for example.

There are two types of reactions in the metabolic pathways, catabolic reactions which involve the breakdown of large complex organic molecules into smaller subunits, which can produce energy, and Anabolic reactions, which in contrary, involve using the energy in order to create new large molecules from previous smaller subunits.

In the catabolic reaction, chemical energy is produced at the shape of ATP (adenosine triphosphate) which is used to boost most of the chemical reactions in the body. In contrary, energy is required in anabolic reactions .and as the two catabolic and anabolic reactions tend to happen at the same time in cells, Anabolic reactions use the ATP released in the catabolic reactions immediately.

The process which produces ATP is called cellular respiration, and it either occurs aerobically, which means it needs oxygen to happen, or anaerobically, which means it doesn't need oxygen to occur.

Both catabolic and anabolic reactions are catalysed by Enzymes which determine the type and speed of the reaction 

Catabolism is the breakdown of complex organic molecules into simpler subunits.

During a catabolic reaction, large molecules carbohydrates, lipids, and proteins are broken down into their simpler subunits, for instance, simple sugars, fatty acids, and amino acids. The chemical energy that is stored up in the covalent bonds in these large molecules is released as these reactions occur, which can be ss this breakdown used to boost other reactions.

Therefore, Catabolic reactions are considered exergonic, meaning that they release or generate more energy than they use.

As for the simpler molecules that are produced at the end of catabolic reactions, they are either got rid of as waste, such as lactic acid, or considered new subunits which can be used to build larger polymers.