General ---------Biology---------------------------------------------------- ------------------Online--------------------------------- Ch. 6  Metabolism of carbohydrates, fats, proteins, nucleic acids

Definition:  Energy is the capacity to do work.

Forms of Energy.  Energy can exist in several forms: kinetic, radiant, chemical and nuclear.  Metabolism is about what cells do as they transform energy from one form to another.

Kinetic energy - the energy of matter in motion ( heat).  This is the most random and least useful form of energy to anabolic chemical reactions. Although we rely on heat energy to keep the temperatures in our bodies within the range that allows our enzymes to work, we are generally unable to take this heat energy and use it to drive anabolic reactions.  Once any form of energy is converted into kinetic or heat energy, it is destined to radiate back into outer space.

Radiant energy - waves in the electromagnetic field of the universe. This includes sunlight, nuclear radiation, visible light, radio and TV waves, in a spectrum ( Fig. 10.5 in text).

To visualize these "waves," think of a wave on the ocean.  The distance from the crest of one wave to the crest of the next is called the wave length.

Sound waves are compression waves in the air.  These waves flow or propagate through the air and through matter.  When a car plays a song with a deep base beat, we can often feel the compression waves going through our matter before we actually hear it.  We experience these waves when we use our ears to hear.  Whales in the ocean send very long sound waves through water.  These compression waves travel for thousands of miles and allow whales to communicate over very long distances.

Electromagnetic waves are waves in the "electromagnetic field."  Like the atmosphere, this "field" surrounds us, but it also exists inside us, in a vacuum, in outer space; it permeates the universe.  We can manipulate this field with magnets, electricity and other indirect means, but it can't be "seen."  Short electromagnetic waves are very strong, e.g. gamma and X-rays.  Longer waves are much weaker,e.g. radio waves.  Visible wave lengths are in the middle of the spectrum.   Your radio dial searches for electromagnetic wavelengths that your favorite station broadcasts on.  These radio waves range from 1 meter to the length of a football field. Microwaves have wavelengths that ranges from 1 meter to 1/1000th of a meter. Visible electromagnetic radiation has hundreds of thousands of wavelengths in a meter.  Gamma rays have billions of wavelengths in a meter.

Chemical energy - energy in covalent bonds in a molecule (calories).  We take in chemical energy in the form of food, and use it to maintain and grow our cells.

Nuclear energy - energy stored in the protons and neutrons of the atomic nucleus. To get this energy you must smash the nucleus, bust the neutrons and protons apart into their component parts.  In the process, some of the matter in these component parts is released as electromagnetic radiation or "nuclear radiation."  E=mc² is Einstein's equation that tells us how much energy we get out of a piece of matter. 

The speed of light is 186,000 miles per second.  Assume you have 1 gram of matter and do the math in the space below.

The most important nuclear radiation for living systems is sunlight.  The sun is one gigantic nuclear explosion that has enough fuel to keep exploding and radiating for several billion years. 

Metabolism is about these energy transformations: nuclear to sunlight, sunlight to plant sugar, plant sugar to antelope, antelope to lion. Bioenergetics is the study of how living systems use and transform this energy.  Economics is fundamentally the study of how human society tracks these energy transformations.