INTRODUCTION
Historically, people secured food through two methods hunting and gathering, and agriculture. Today, most of the food energy consumed by the world population is supplied by the food industry. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells in an effort to produce energy, maintain life, or stimulate growth.
NUTRITIONAL PROCESSES
Food: Is any substance consumed to provide nutritional support for the body.
Nutrition: Is the intake of food, considered in relation to the body’s dietary needs. It can be also defined as the science of food and its relation to health. It includes good diet, digestion and metabolism. It is also expressed as the sum of the processes involved in taking in nutrients and assimilating and utilizing them. Nutrients are highly essential and necessary for growth, maintenance, repair of the human body
Good nutrition : Is an adequate, well balanced diet combined with regular physical activity : Is a cornerstone of good health. Poor nutrition can lead to reduced immunity, increased susceptibility to disease, impaired physical and mental development, and reduced productivity.
DEFINITIONS OF TERMS
Ingestion: Is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms, ingestion can take place through taking the substance through the cell membrane Ingestion is the taking in of food or other substances.
Digestion: Refers to the breakdown of food into smaller particles, capable of later absorption.
In humans, the mouth is the portal of "ingestion", whereas most" digestion" occurs in the stomach and bowel. These are the processes that happen in the digestive system:
Ingestion (Eating) → Digestion (Breaking Down) → Absorption → Egestion
Absorption: Digested food molecules are absorbed in the small intestine. This means that they pass through the wall of the small intestine and into our bloodstream. Once in the bloodstream, the digested food molecules are carried around the body to where they are needed. The inside wall of the small intestine needs to be thin, with a really big surface area. This allows absorption to happen quickly and efficiently. If the small intestine had a thick wall and a small surface area, a lot of digested food might pass out of the body before it had a chance to be absorbed. To get a big surface area, the inside wall of the small intestine is lined with tiny villi (one of them is called a villus). These stick out and give a big surface area. They also contain blood capillaries to carry away the absorbed food molecules. Digested food molecules are absorbed in the small intestine. This means that they pass through the wall of the small intestine and into our bloodstream. Once in the bloodstream, the digested food molecules are carried around the body to where they are needed.
Egestion
Excess water is absorbed back into the body in the large intestine. What is left then is undigested food. This is stored in the rectum, the lower part of the large intestine, until we are ready to go to the toilet. It then comes out of the rectum through the anus as faeces. This process is called egestion
It is the discharge or expulsion of undigested material (food) from a cell in case of unicellular organisms, and from the digestive tract via the anus in case of multicellular organisms.It should not be confused with excretion, which is getting rid of waste formed from the chemical reaction of the body, such as in urine, sweat. It is the removal of undigested food or faeces from the gut. In most animals egestion takes place via the anus, although the invertebrate flatworms must use the mouth because their gut has no exit. Egestion refers solely to indigestible matter which is never absorbed into the cells – it should not be confused with excretion of the waste products of metabolism.
Excretion : Is the transfer of substances out of a living organism into its environment. At its simplest, for single-cell forms of life, this involves extrusion across the cell membrane of the unwanted or potentially toxic by-products of respiration and metabolism.
Assimilation: Is the combination of two processes to supply animal cells with nutrients. It can also be defined as the conversion of nutrients into fluid or solid substance of the body by the process of either absorption or digestion.
- The conversion of nutriment into a useable form (e.g. liquid or solid) that is incorporated into the tissues and organs following the processes of digestion.
- The chemical alteration of substances in the bloodstream by the liver or cellular secretions.
Metabolism (from Greek: μεταβολή metabolē, "change" or Greek: μεταβολισμός metabolisms, "out throw") is the set of life-sustaining chemical transformations within the cells of living organisms. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments.
The word metabolism can also refer to all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which case the set of reactions within the cells is called intermediary metabolism or intermediate metabolism.
CATEGORY OF METABOLISM
Metabolism is usually divided into two categories:
[1] Catabolism: Breaks down organic matter, for example to harvest energy in cellular respiration. Is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions.
[2] Anabolism: Is the set of constructive metabolic processes where the energy released by catabolism is used to synthesize complex molecules. Absorption and egestion. Anabolism uses energy to construct components of cells such as proteins and nucleic acids.
