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Chemical Messenger Research Paper

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A hormone is a type of chemical messenger that allows communication between cells. Hormones are concealed by the glands of the endocrine system and they help to maintain homeostasis and to regulate reproduction and development. Glands of the endocrine system secrete hormones right into the extracellular environment. The hormones then diffuse to the bloodstream by capillaries and are transported to the target cells. Hormones are molecules that generally apply effects at sites other than that from which they were produced and secreted.
Hormone cells are typically of a particular cell type, residing within a certain endocrine gland, such as thyroid gland, ovaries, and testes. Hormones exit their cell of origin through the process of exocytosis
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Changes in the concentration of small molecules, called second messengers, constitute the next step in the molecular information circuit. Particularly important second messengers include cyclic AMP and cyclic GMP, calcium ion, inositol 1,4,5-trisphosphate, (IP3), and diacylglycerol. The use of second messengers has several consequences. First, second messengers are often free to diffuse to other compartments of the cell, such as the nucleus, where they can influence gene expression and other processes. Second, the signal may be amplified significantly in the generation of second messengers. Enzymes or membrane channels are almost always activated in second-messenger generation; each activated macromolecule can lead to the generation of many second messengers within the cell. Thus, a low concentration of the signal in the environment, even as little as a single molecule, can yield a large intracellular signal and response. Third, the use of common second messengers in multiple signaling pathways creates both opportunities and possible problems. Input from several signaling pathways, often called cross talk, may affect the concentrations of common second messengers. Cross talk permits more finely tuned regulation of cell activity than would the action of individual independent pathways. However, unsuitable cross talk can cause second messengers to be
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