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The Chemistry of Animal Life

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The Chemistry of Animal Life
Photo © ElementalImaging / iStockphoto.

Animals, like all lifeforms, are composed of and dependent upon an assortment of chemical compounds. To understand the chemistry of life, we need to first understand the basics of general chemistry. So to begin, here are some definitions:

  • matter - anything that occupies space and has mass (matter includes things that are solids, liquids, gases)
  • mass - the amount of matter in an object
  • element - the most basic unit of matter; a substance that cannot be decomposed into simpler substances by chemical or physical means
  • atom - the smallest component of an element having the chemical properties of the element
  • protons - postively charged particles located in the nucleus of an atom (p+)
  • neutrons - uncharged particles in the nucleus of an atom
  • electrons - negatively charged particles that move around the nucleus (e-)
  • atomic mass - each element has an atomic mas which is the number of neutrons and protons in the atom's nucleus
  • atomic number - each element has an atomic number which is the number of protons in the nucleus of one of the element's atoms
  • molecule - a bonded collection of two or more atoms of the same or different elements
  • compound - a substance with constant composition that can be broken down into elements by chemical processes

The elements that naturally occur in animals include (in order of descending percent body weight, approx):

  • oxygen (65%)
  • carbon (19%)
  • hydrogen (10%)
  • nitrogen (3%)
  • calcium (1%)
  • phosporus (1%)
  • potassium (0.2%)
  • sulfur (0.1%)
  • sodium (0.1%)
  • chlorine (0.1%)
  • magnesium (0.1%)
  • manganese (0.1%)
  • iron (0.1%)
  • copper (0.1%)
  • iodine (0.1%)

Molecules can be subdivided into two main groups, those that contain carbon, organic molecules and those that lack carbon, inorganic molecules. The chemistry of the organic molecules is influenced primarily by the characteristics of carbon. Carbon atoms bond together with other carbon atoms to form chains and rings of a wide range of lengths and configurations. Some examples of organic molecules include:

  • carbohydrates - animals' main source of energy
  • lipids - building blocks of fats, make up cell parts and supply energy
  • proteins - structural material, hormones, enzymes, metabolic functions, endocrine functions
  • nucleotides - building blocks of nucleic acids, DNA and RNA
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