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Zymogens
In biochemistry, a zymogen (), also called a proenzyme (), is an inactive precursor of an enzyme. A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme. The biochemical change usually occurs in Golgi bodies, where a specific part of the precursor enzyme is cleaved in order to activate it. The inactivating piece which is cleaved off can be a peptide unit, or can be independently-folding domains comprising more than 100 residues. Although they limit the enzyme's ability, these N-terminal extensions of the enzyme or a “prosegment” often aid in the stabilization and folding of the enzyme they inhibit. The pancreas secretes zymogens partly to prevent the enzymes from digesting proteins in the cells in which they are synthesised. Enzymes like pepsin are created in the form of pepsinogen, an inactive zymogen. Pepsinogen is activated when chief cel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digestive Enzyme
Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of animals (including humans) and in the tracts of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular survival. Digestive enzymes of diverse specificities are found in the saliva secreted by the salivary glands, in the secretions of cells lining the stomach, in the pancreatic juice secreted by pancreatic exocrine cells, and in the secretions of cells lining the small and large intestines. Digestive enzymes are classified based on their target substrates: * Lipases split fatty acids into fats and oils. *Proteases and peptidases split proteins into small peptides and amino acids. *Amylases split carbohydrates such as starch and sugars into s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coagulation
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. Coagulation begins almost instantly after an injury to the endothelium lining a blood vessel. Exposure of blood to the subendothelial space initiates two processes: changes in platelets, and the exposure of subendothelial tissue factor to plasma factor VII, which ultimately leads to cross-linked fibrin formation. Platelets immediately form a plug at the site of injury; this is called ''primary hemostasis. Secondary hemostasis'' occurs simultaneously: additional coagulation (clotting) factors beyond factor VII ( listed below) respond in a cascade to form fibrin strands, which strengthen the platelet plug. Disorders of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pancreas
The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an endocrine and a digestive exocrine function. 99% of the pancreas is exocrine and 1% is endocrine. As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin, and pancreatic polypeptide. As a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum through the pancreatic duct. This juice contains bicarbonate, which neutralizes acid entering the duodenum from the stomach; and digestive enzymes, which break down carbohydrates, proteins, and fats in food entering the duodenum from the stomach. Inflammation of the pancreas is known as pancreatitis, with common causes including chronic alcohol use and gallstones. Becaus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
