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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.
Calcitonin is a naturally occurring hormone. In women who are at least 5 years beyond menopause, it slows bone loss and increases spinal bone density.
Certain rare plants containing cyanide include apricot pits and a type of potato called cassava. Fortunately, only chronic or massive ingestion of any of these plants can lead to serious poisoning.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
Fungal nail infections account for up to 30% of all skin infections. They affect 5% of the general population—mostly people over the age of 70.