Once formed proteins only exist for a certain period of time and are then degraded and recycled by the cell’s machinery through the process of protein turnover. A protein’s lifespan is measured in terms of its half-life and covers a wide range. They can exist for minutes or years with an average lifespan of 1-2 days in mammalian cells. Abnormal and or misfolded proteins are degraded more rapidly either due to being targeted for destruction or due to being unstable.
Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in virtually every process within cells. Many proteins are enzymes that catalyze biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. Proteins are also necessary in animals’ diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids from food. Through the process of digestion, animals break down ingested protein into free amino acids that are then used in metabolism.
Morphine (INN) (/Л€mЙ”rfiЛђn/) (sold under nearly a hundred trade names) is an opioid analgesic drug, a recreational drug, and the main psychoactive chemical in opium. In clinical medicine, morphine is regarded as the gold standard, or benchmark, of analgesics used to relieve intense pain and suffering. Like other opioids, such as oxycodone, hydromorphone, and diacetylmorphine (heroin), morphine acts directly on the central nervous system (CNS) to relieve pain.
In controlled studies comparing the physiological and subjective effects of heroin and morphine in individuals formerly addicted to opiates, subjects showed no preference for one drug over the other. Equipotent, injected doses had comparable action courses, with no difference in subjects’ self-rated feelings of euphoria, ambition, nervousness, relaxation, drowsiness, or sleepiness. Short-term addiction studies by the same researchers demonstrated that tolerance developed at a similar rate to both heroin and morphine. When compared to the opioids hydromorphone, fentanyl, oxycodone, and pethidine/meperidine, former addicts showed a strong preference for heroin and morphine, suggesting that heroin and morphine are particularly susceptible to abuse and addiction. Morphine and heroin were also much more likely to produce euphoria and other positive subjective effects when compared to these other opioids. The choice of heroin and morphine over other opioids by former-drug addicts may also be the result of the fact that heroin (also known as morphine diacetate, diamorphine or di-acetyl-morphine) is an ester of morphine and a morphine prodrug, essentially meaning that they are identical drugs in vivo. Heroin is converted to morphine before binding to the opioid receptors in the brain and spinal cord, where morphine then causes the subjective effects, which is what the addicted individuals are ultimately looking for.
Most of the licit morphine produced is used to make codeine by methylation. It is also a precursor for many drugs including heroin (3,6-diacetylmorphine), hydromorphone (dihydromorphinone), and oxymorphone (14-hydroxydihydromorphinone); many morphine derivatives can also be manufactured using thebaine and/or codeine as a starting material. Replacement of the N-methyl group of morphine with an N-phenylethyl group results in a product that is 18 times more powerful than morphine in its opiate agonist potency. Combining this modification with the replacement of the 6-hydroxyl with a 6-methylene group produces a compound some 1,443 times more potent than morphine, stronger than the Bentley compounds such as etorphine (M99, the Immobilon® tranquilliser dart) by some measures.