General Discussion about Photosynthesis and Light

Photosynthesis is a chemical process whose name almost everyone who's ever gone to school will be familiar with. Most people however fail to realize how vitally important this process is for life on Earth or what a mystery its workings are.

First let's brush off our high-school chemistry and take a look at the formula for the photosynthesis reaction:

6H2O + 6CO2 +Sunlight --> C6H12O6 + 6O2
Glucose

Translated into words this means: Water and carbon dioxide and sunlight produces glucose and oxygen.

To be more exact what is happening in this chemical reaction is that six molecules of water (H2O) combine with six molecules of carbon dioxide (CO2) in a reaction that is energized by sunlight. When the reaction is complete, the result is a single molecule of glucose ( C6H12O6), a simple sugar that is a fundamental element of nutrition-, and six molecules of gaseous oxygen (O2). The source of all nutriments on our planet, glucose contains a great deal of energy.

Simple though this reaction may look, it is in fact incredibly complex. There is only one place where it occurs: in plants. The plants of this world produce the basic food for all living things. Every other living thing is ultimately nourished in one way or another by glucose. Herbivorous animals eat the plants themselves and carnivorous animals eat plants and/or other animals. Human beings are no exception: our energy is derived from the food we eat and comes from the same source. Every apple, potato, chocolate, or steak or anything else you eat is supplying you with energy that came from the sun.

But photosynthesis is important for another reason. The reaction has two products: in addition to glucose, it also releases six molecules of oxygen. What's happening here is that plants are continuously cleaning up an atmosphere that is constantly being "polluted" by air-breathing creatureshuman beings and animals, whose energy is derived from combustion in oxygen, a reaction that produces carbon dioxide. If plants didn't release oxygen, the oxygen-breathers would eventually use up all the free oxygen in the atmosphere and that would be the end of them. Instead, the oxygen in the atmosphere is constantly being replenished by plants. Without photosynthesis, plant life could not exist; and without plant life, there would be no animal or human life. This marvelous chemical reaction, which has never been duplicated in any laboratory, is taking place deep in the grass you step on and in trees you may not even notice. It once occurred in the vegetables on your dinner plate. It is one of the fundamental processes of life.

The interesting thing is what a carefully-designed process photosynthesis is. When we study it, we can't help but observe that there is a per- fect balance between plant photosynthesis and the energy consumption of oxygen-breathers. Plants supply glucose and oxygen. Oxygen-breathers burn the glucose in the oxygen in their cells to get energy and they release carbon dioxide and water (in effect, they're reversing the photosynthesis reaction) that the plants use to make more glucose and oxygen. And so it goes on, a continuous cycle that is called the "carbon cycle" and it is powered by the energy of the sun.

In order to see how perfectly-created this cycle truly is, let us focus our attention on just one of its elements for the moment: the sunlight. In the first part of this article we looked at sunlight and found that its radiation components were specially tailored to allow life on Earth. Could sunlight also be deliberately tailored for photosynthesis as well? Or are plants flexible enough so that they can perform the reaction no matter which kind of light reaches them?

The American astronomer George Greenstein discusses this in The Symbiotic Universe: Chlorophyll is the molecule that accomplishes photosynthesis... The mechanism of photosynthesis is initiated by the absorption of sunlight by a chlorophyll molecule. But in order for this to occur, the light must be of the right color. Light of the wrong color won't do the trick.

Agood analogy is that of a television set. In order for the set to receive a given channel it must be tuned to that channel; tune it differently and the reception will not occur. It is the same with photosynthesis, the Sun functioning as the transmitter in the analogy and the chlorophyll molecule as the receiving TV set. If the molecule and the Sun are not tuned to each other-tuned in the sense of colour- photosynthesis will not occur. As it turns out, the sun's color is just right.

Some evolutionists hold that "if conditions had been different, life would have evolved to be perfectly in harmony with them as well". Thinking superficially about photosynthesis and plants, one could come to a similar conclusion: "If sunlight were different, plants would have just evolved according to that." But this is in fact impossible. Although he's an evolutionist himself, George Greenstein admits this: One might think that a certain adaptation has been at work here: the adaptation of plant life to the properties of sunlight. After all, if the Sun were a different temperature could not some other molecule, tuned to absorb light of a different colour, take the place of chlorophyll? Remarkably enough the answer is no, for within broad limits all molecules absorb light of similar colours. The absorption of light is accomplished by the excitation of electrons in molecules to higher energy states, and the same no matter what molecule you are discussing. Furthermore, light is composed of photons, packets of energy and photons of the wrong energy simply can not be absorbed… As things stand in reality, there is a good fit between the physics of stars and that of molecules. Failing this fit, however, life would have been impossible.

What Greenstein is saying briefly is this: No plant can only perform photosynthesis except within a very narrow range of light wavelengths. And that range corresponds exactly to the light given out by the sun. The harmony between stellar and molecular physics that Greenstein refers to is a harmony too extraordinary ever to be explained by chance. There was only one chance in 1025 of the sun's providing just the right kind of light necessary for us and that there should be molecules in our world that are capable of using that light. This perfect harmony is unquestionably proof of intentional, deliberate design.

By Peter Zeka