Begin is the common term: to begin knitting a sweater. Commence is a more formal word, often suggesting a more prolonged or elaborate beginning: to commence proceedings in court. Initiate implies an active and often ingenious first act in a new field: to initiate a new procedure.
Structure of the trp operon. The trp operon is an operon â a group of genes that are used, or transcribed, together â that codes for the components for production of tryptophan. The trp operon is present in many bacteria, but was first characterized in Escherichia coli.The operon is regulated so that when tryptophan is present in the environment, the genes for tryptophan synthesis are not expressed.It was an important experimental system for learning about gene regulation, and is commonly used to teach gene regulation.he trp operon is present in many bacteria, but was first characterized in Escherichia coli. The operon is regulated so that when tryptophan is present in the environment, the genes for tryptophan synthesis are not expressed.
As you might expect, secretion from the exocrine pancreas is regulated by both neural and endocrine controls. During interdigestive periods, very little secretion takes place, but as food enters the stomach and, a little later, chyme flows into the small intestine, pancreatic secretion is strongly stimulated. As soon as this occurs, the enyzmes secreted by the acinar cells are flushed out of the pancreas, through the pancreatic duct into the duodenum. 2  Gastrin: This hormone, which is very similar to cholecystokinin, is secreted in large amounts by the stomach in response to gastric distention and irritation.