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The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
According to animal studies, the typical American diet is damaging to the liver and may result in allergies, low energy, digestive problems, and a lack of ability to detoxify harmful substances.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
There are major differences in the metabolism of morphine and the illegal drug heroin. Morphine mostly produces its CNS effects through m-receptors, and at k- and d-receptors. Heroin has a slight affinity for opiate receptors. Most of its actions are due to metabolism to active metabolites (6-acetylmorphine, morphine, and morphine-6-glucuronide).
Many of the drugs used by neuroscientists are derived from toxic plants and venomous animals (such as snakes, spiders, snails, and puffer fish).