Biology of Animals

Biology of Animals - 1402 Chapter 2 Nitrogen, Carbon,...

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1402 Chapter 2 Nitrogen, Carbon, Hydrogen and Oxygen make up 96% of the human body. Compounds consists of two or more elements in a fixed ratio. Sugar contains carbon, hydrogen, and oxygen in a fixed ratio. Elements such as iodine, iron, and copper are needed in amounts less than 0.01%. Despite the small amounts, these elements are required for vital functions. Deficiency in iodine, for example, can produce a goiter, a large swelling in the neck. Electrons are negatively charged particles. In a neutral atom, the number of electrons is equal to the number of protons. When an atom loses or gains electrons, its charge becomes positive or negative, respectively. Covalent bonds, which involve sharing electrons, are the strongest bonds. All the other bond types are a form of ionic interaction. Ionic bonds are the second strongest and hydrogen bonds are the weakest. As heat is absorbed by the water molecules, the hydrogen bonds break. These molecules that have the greatest energy leave as sweat evaporates from your skin. The surface of the liquid
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