WE HUMANS ARE SOLAR POWERED

You may not have thought about it, but the energy you use for all your bodily activities and functions are fueled by second hand solar energy.  We, like all other animals, cannot harness solar energy directly, but must rely on plants to capture it and store it in a form 'palitable' to us.  Through a process called photosynthesis, molecules of carbon dioxide from the air and water from the soil are captured by plants and are taken apart.  They are then re-assembled into molecules of a simple sugar called glucose consisting of carbon, hydrogen and oxygen.  It takes six molecules of carbon dioxide and six of water to make one molecule of glucose. The breaking down and re-assembing of the molecules is powered by solar energy, some of which is stored in the electrical bonds that hold the glucose atoms together.  Luckily for us, there is some leftover oxygen in this process--a waste product that plants excrete into the air serving to replenish our oxygen supply. 

Of course, plants are not doing all this work just for us.  Some of the glucose they make is used to fuel their own life styles.  In fact, they link some one thousand glucose molecules together to form starch which they stash away for their future energy needs.  Although plants are rather good at converting solar energy to sugar, the process is not 100% efficient.  Nature demands that with any energy conversion some energy must always be lost as heat.  In we humans, this wasted heat is what keeps our bodies warm.

Human cells, like those of all animals and plants, can reverse photosynthesis by burning glucose in a slowly, controlled manner, a process called metabolism.  The stored solar energy is released to power their own growth and development.  Like any combustion, the process gives off two by-products, water and carbon dioxide--the original substances consumed by the plants.  To carry out this chemical reaction, cells need some additional oxygen atoms.  In the case of humans, the oxygen is obtained from the air we breath and is carried by our blood stream to all the cells of our bodies.

To sum it all up then:  Nature stores solar energy in a sugar that when metabolized powers all living things on Earth.