HORMONE secreted by beta cells of the pancreatic islets.It is considered to be the PRIMARY anabolic hormone present inside our body.It maintains the metabolism of carbohydrates, fats and protein by promoting the absorption of glucose from the blood into the liver, fat and skeletal muscle cells.In these tissues, the absorbed glucose is changed into either glycogen via glycogenesis or fats (triglycerides) via lipogenesis, or, in the case of the liver, into both.Protein:Protein, a highly complex substance that is present in all living organisms.Proteins are of great nutritional value and are directly involved in the chemical processes essential for life.The importance of proteins was recognized by chemists in the early 19th century, including Swedish chemist Jöns Jacob Berzelius, who in 1838 coined the term protein, a word derived from the Greek prōteios, meaning “holding first place.”Proteins are species-specific; that is, the proteins of one species differ from those of another species.They are also organ-specific; for instance, within a single organism, muscle proteins differ from those of the brain and liver.Fat:Fat, any substance of plant or animal origin that is nonvolatile, insoluble in WATER, and oily or greasy to the touch.Fats are usually solid at ordinary temperatures, such as 25 °C (77 °F), but they begin to liquefy at somewhat higher temperatures.Chemically, fats are identical to animal and vegetable oils, consisting primarily of glycerides, which are esters formed by the reaction of three molecules of FATTY acids with one molecule of glycerol.Vitamin:Vitamin, any of several organic substances that are necessary for small quantities for normal health and growth in higher forms of animal life.Vitamins are distinct in several ways from other biologically important compounds such as proteins, carbohydrates, and lipids.Although these latter substances also are indispensable for proper bodily functions, almost all of them can be synthesized by animals in adequate quantities.Vitamins, on the other hand, generally cannot be synthesized in amounts sufficient to meet bodily needs and therefore must be obtained from the diet or from some synthetic source.If a vitamin is absent from the diet or is not properly absorbed by the body, a specific deficiency disease may develop.Carbohydrate:Carbohydrate, class of naturally occurring compounds and derivatives formed from them. In the early part of the 19th century, substances such as wood, starch, and linen were found to be composed mainly of molecules containing atoms of carbon (C), hydrogen (H), and oxygen (O).Carbohydrates are probably the most abundant and widespread organic substances in nature.They are essential constituents of all living things.Carbohydrates are formed by green plants from carbon dioxide and water during the process of photosynthesis.Carbohydrates serve as ENERGY sources and as essential structural components in organisms.In addition, part of the structure of nucleic acids, which contain genetic information, consists of carbohydrate.