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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.
Elderly adults are living longer, and causes of death are shifting. At the same time, autopsy rates are at or near their lowest in history.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
In the United States, an estimated 50 million unnecessary antibiotics are prescribed for viral respiratory infections.
Adolescents often feel clumsy during puberty because during this time of development, their hands and feet grow faster than their arms and legs do. The body is therefore out of proportion. One out of five adolescents actually experiences growing pains during this period.