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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.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Essential fatty acids have been shown to be effective against ulcers, asthma, dental cavities, and skin disorders such as acne.
Adult head lice are gray, about ? inch long, and often have a tiny dot on their backs. A female can lay between 50 and 150 eggs within the several weeks that she is alive. They feed on human blood.
Asthma occurs in one in 11 children and in one in 12 adults. African Americans and Latinos have a higher risk for developing asthma than other groups.