Measuring Energy and Its Forms

Measuring Energy

I mentioned that energy is quantifiable.  That is, we can measure it.  Over time we have come up with a number of different definable measurements.   Just like we measure, say, length as inches, yards, meters etc.  we have different ways of discussing amounts of energy.   

There are two units that are used in nutrition.  One is the Kilojoule (KJ) – named after Jame Prescott Joule (. . . ..  Not that it matters right now, but for definition buffs, it is the amount of energy needed to move a mass of one kilogram, 1 meter.   In countries other than the U.S. you will often find the energy content of foods measured in Kj's.  

In the U.S. the unit we are all familiar with is the Calorie.  The Calorie is the amount of heat necessary to heat a kilogram (about 2.2 lbs)  of water 1 degree Celsius, and equals a bit over 4 Kj.

(Word of caution, the "Calorie" - uppercase C, that is used in food energy is 1000 times as much as the "calorie" - lowercase c that often shows up in scientific research.  Although most of the science world is now unified on the joule or the Kilojoule.)

Of course the word “Calorie” brings to many of us in the modern western world a sense of foreboding, a shudder goes through our sensibilities.  We have come to dread that word and think of Calories, and therefore food energy, as a bad thing. This is because we live in a unique time in history when much of the western world suffers under the weight of excess calories rather than too few.  We will discuss this rather prejudicial view presently.  But for the time being, let’s remain clinical and, if possible, be willing to accept a broader view of the importance of food energy.

Very often you will see a food advertised as low in Calories but high in energy.  Well, this is perfect nonsense of course.  Its like saying your house is very tiny but has a very large square footage.  The implication is that this is not offering food value, but, presumably some sort of drug like caffeine that get the juices flowing, and comes about because the multiple meanings of the world "energy."

Forms of Energy

One aspect about energy that leads to confusion in every beginning science student is the fact that energy comes in several different interchangeable forms.  It routinely morphs from one form to another.  Interestingly, it is not destroyed - the amount in the universe, as best we can tell, remains constant.*(For the science buffs, Einstein pointed out that energy is also interchangeable with mass – famous equations E = mc2, but lets not go there).  It isn't born, it doesn't die, it just changes form.

In understanding food energy and what we do with it we have to be acquainted with several forms. You don't need to memorize this or anything.  Just know that they exist and that the each are of importance to our bodies and our lives.   

First: Solar energy, sometimes called radiant energy.  The sun produces staggering amounts of energy that is radiated out into the universe.  Some of it hits the earth.  That’s a good thing. 

Second: is chemical energy – this is a stored form of energy which is contained within the structure of chemicals or molecules.  And, I might add, your body.

Third: mechanical energy – the form that actually does the work.  Our bodies are constantly converting stored chemical energy into mechanical energy.  My typing on the keyboard, and you moving your eyes from left to right are examples of mechanical energy in use.

Finally: we will be discussing heat.  

All of these are interchangeable, all are measured in Kilojoules or Calories.  We will stick to Calories.

The next question is where does the energy that we get from our food, come from originally?

So - Where does the Energy in Food Come From?

So - Where does the Energy in Food Come From?

In a word – the sun.  That’s right, you are running on solar energy at this moment.  Every blink of the eye, heart beat, synapse connection, breath you take – from the sun.  

Lying out in the sun to rejuvenate yourself, however, will likely produce nothing more than a good sunburn.  You are simply incapable of accessing this marvelous energy source for your own biological purposes.  Good thing, too.  Otherwise sunshine could make us fat and who wants that.

You are absolutely reliant on intermediaries to collect that sunlight and convert it to a form that your body can access.  

Enter – plants.  This might be an appropriate time for you to take a step outside and hug a tree or kiss a bush.  These are your friends.  Even those dandelions you pulled out of your lawn last week – biological associates.  

Plants have the ability to trap the energy of sunshine into chemical structures that we can then eat and utilize.  This is no small thing. No plants, no you.  

Wait, say you, I eat cows for food, none of that wimpy plant stuff.   Well, not that I necessarily endorse this particularly culinary plan, you are still running off of solar energy.  The cow got its energy from grass or grain.  You might eat meat from a lion that ate a hyena, which ate a gazelle.  The gazelle ate plants.  It will always come back to somebody that can gather up radiant energy and turn it into chemical energy for the rest of us.  Hence, the lowly plant is at the bottom of the food chain, because of its incredible energy mining capabilities.

Now, I will be using the word "plants" fairly consistently.  What I mean, for those who are fussy about such things, is "photo synthesizers", a term that includes all living things  that can gather and store energy from the sun.  That would include plankton, in the oceans, little tiny microscope beings, certain bacteria, etc.  These guys do make up a large and important group of organisms that are busy collecting sunlight and providing food energy for other creatures.  But, in an effort to keep things relatively simple, we will usually refer to "photo synthesizers" by the somewhat inaccurate term of "plants".

Up next - how do they do it?

The Linchpin of Life - Photosynthesis

The Linchpin of Life - Photosynthesis

I say, without hesitation, that this is the most important process of life as we know it.  No one should graduate from high school, be involved in public policy or industry, be a religious leader, be a parent or just be a person who cares about the future without a complete and thorough understanding this process, how it works and why it is critical.  It is the source of virtually all of our energy (with the exceptions of nuclear and geothermal energy) and key to understanding and solving most of our environmental problems  including global warming.

And yet, when most people are asked what "photosynthesis" is they give a "who cares" shrug of their shoulders.  Clearly the priorities of our education system are a tad confused.  

On the off chance that it may not be completely clear to you, you might want to stay tuned. . .


Photosynthesis sounds a bit like chemistry or, well boring.  It does, after all, have 5 syllables.  Let's break it down.

Photo means "light".  (Photography = picture (graph) from light)
Synthesis means "make or produce".

Photosynthesis simply means to make something from light.  Not so bad - right?

Make what?     Sugar.

Yes, sugar that stuff we love and love to hate.  Try for a bit to drop your prejudices one way or another; we will be talking a lot more about sugar and all its relatives shortly.  Just take my word for it right now that it is really really important and we should be very grateful for it.

Photosynthesis is dance of four substances (your science teacher called them chemical compounds,  but substances will do).

Water, carbon dioxide, sugar and oxygen.

What a plant can do, that you and I cannot, is take water, combine it with carbon dioxide and, given sunlight, produce sugar and oxygen.

carbon dioxide + water + sunlight   =     sugar + oxygen.

 (  For those who like the chemical explanation:

6CO2 + 6H20 + solar energy = C6H12O6 + 6O2  )

It is worth noting that at this point, oxygen is just a waste product because, chemically, there are too many oxygen atoms left over, so they are jettisoned.

The energy from the sun is held in the sugar molecule - sort of like a little battery.  

Whether you are in a well trimmed garden, an ancient forest, or a weed covered lot, you are seeing literally trillions and trillions of little factories trapping sunlight into sugar molecules made from water and carbon dioxide, and filling the atmosphere with needed oxygen - making life possible for the rest of us. 

Up next:  What does the plant do with all these trillions of sugar molecules?