Cycling Chemicals

To create energy, carbohydrates are broken down by aerobic respiration.  The process starts when the carbohydrate reacts with oxygen and is broken into carbonic gas and water.  This results is a release of energy.  Cellular respiration is the process where stored energy is liberated for use in metabolism.  Another process of energy liberation is fermentation and this takes place in some fungi, notably yeasts, and bacteria.  The by-products are carbon-dioxide and alcohol.

The primary elements that make up organic matter are carbon (C), hydrogen (H) and oxygen (O).  Nitrogen (N) is essential in making amino acids, which are the main building-blocks of life processes.   Water acts as the universal solvent and transportation medium for life processes.  Other minerals, like phosphorus (P), sulfur (S), calcium (Ca), sodium (Na), potassium (K)  and magnesium (Mg), are essential in constructing the molecules of living things.

These elements are carried through the non-living environment - water, atmosphere, soil and lithosphere - to become part of a living organism, then re-enter this realm after an organism's death, or through an organism's waste processes (respiration and excretion).   This is known as the Matter or Biogeochemical Cycle and is  integral with food chains.

Unlike energy transfer that flows in one direction, matter is continuously cycled: chemical elements are removed from the non-living environment, used by organisms and later returned to it.   All nutrients are cycled, but here only the key ones will be considered.

Water Cycle
Carbon Cycle
Oxygen Cycle
Nitrogen Cycle


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