Green Breath

The Miracle of Photosynthesis

The Earth is a planet specially designed to support life. The Earth provides an environment that can sustain life, thanks to the many very sensitive balances set up on it, from the gas levels in the atmosphere to its distance from the sun, from the existence of mountains to the presence of drinking water, from the wide variety of plants to the temperature of the Earth.

If the components which make up life are to survive, both the physical and the biological balances have to be maintained. For example, in the same way as gravity is indispensable for living things to live on the ground, so the substances plants produce are just as necessary for the survival of life.

As we indicated earlier, the process which plants carry out to produce these organic substances is called photosynthesis. The process of photosynthesis, which can be summarized as plants' producing their own food, is what makes them different from other living things. What makes this difference is the existence of structures in plant cells (unlike human or animal cells), which can make direct use of sunlight. With the help of these structures, plant cells turn the energy from the sun, which human beings and animals absorb by means of food, into energy and store it, again by special means. In this way, the process of photosynthesis is completed.

Of course, it is not the plant itself which carries out this process, nor the leaves, nor even the totality of the plant cells. It is a small organ found in plant cells called the "chloroplast," which gives plants their green color and carries out these processes. Chloroplasts are one thousandth of a millimeter in size, for which reason they can be seen only through a microscope. The wall of the chloroplast, which plays such an important role in photosynthesis, is just one hundred millionth of a meter in size. As we can see, these figures are extremely small, and all the processes take place in this microscopic environment. This is one of the astounding features of photosynthesis.

The Chloroplast: A Factory Full of Secrets

In a chloroplast there are various formations such as thylakoids, internal and external membranes, stromata, enzymes, ribosomes, RNA, and DNA to bring about photosynthesis. These formations are all interlinked, both structurally and in terms of their functions, and each one has very important functions which it carries out within its own body. For example, the chloroplast's outer membrane regulates the flow of materials into and out of each chloroplast. The internal membrane system consists of flattened sacs, or thylacoids which resemble discs. Pigment molecules (chlorophylls) and enzymes essential for photosynthesis are embedded in the thylakoids. Many of the thylakoids are stacked, forming structures called "grana," which allow maximum absorption of sunlight. This means the plant absorbing more light and being able to carry out more photosynthesis.

Surrounding the thylakoids is a lipid solution, the "stroma," which contains other enzymes as well as DNA, RNA, and ribosomes. With the DNA and ribosomes they possess, chloroplasts both reproduce and produce certain proteins.

Another important point in photosynthesis is that all these processes take place in a period of time so short as to be unobservable. The thousands of chlorophylls found in chloroplasts simultaneously produce their reaction to sunlight in the unbelievably short time of a thousandth of a second.
While scientists describe the photosynthesis event in chloroplasts as a long chemical chain reaction, they are unable to explain some parts of what happens in this chain on account of that speed, and simply look on in amazement. But it is clearly understood that photosynthesis involves two stages. These are known as the "light reactions" and the "dark reactions."

The Light Reactions

Radiations from the sun form a continuous series. The range of radiations that organisms detect with their eyes – visible light – is roughly the same range plants use. Shorter wavelengths (blue light) are more energetic than longer wavelengths (red light). Pigments are substances that absorb visible light; different pigments absorb different wavelengths. Chlorophyll, the main pigment of photosynthesis, absorbs light primarily in the blue and red regions of the visible spectrum. Green light is not appreciably absorbed by chlorophyll; instead, it is reflected. Plants usually appear green because their leaves reflect most of the green light that strikes them.

The process of photosynthesis starts with the absorption of sunlight by these pigments, which make plants look green. But how do the chlorophylls begin the process of photosynthesis by absorbing sunlight? In order to answer this question it will be useful to first of all examine the structure of the thylakoid, which is found inside the chloroplasts and contains the chlorophylls within it.

There are two types of chlorophylls, "chlorophyll-a" and "chlorophyll-b." The light dependent reactions of photosynthesis begin when chlorophyll a and accessory pigments absorb light. As we can see in the picture where the detailed structure of the thylakoid is explained, chlorophyll molecules, accessory pigments, and associated electron acceptors are organized into units called photosystems.

There are two types of photosystems, Photosystem I and Photosystem II. The light energy is transferred to a special "chlorophyll-a" molecule called the reaction center. The energy obtained from the absorption of sunlight gives rise to the loss of energy-rich electrons in the reaction centres. These energy-rich electrons are used in subsequent stages to obtain oxygen from water.

At this stage there is a flow of electrons. The electrons lost by "Photosystem I" are replaced by electrons lost from "Photosystem II." Electrons lost by "Photosystem II" are replaced by electrons removed from the water. As a result, water is separated into oxygen, protons, and electrons.

At the end of the electron flow, the electrons, along with the protons from water are transported to the inside of the thylakoid and combine with a hydrogen-carrier molecule NADP+ (nicotinamide adenine dinucleotide phosphate). The molecule NADPH results from this.

As electrons flow from carrier to carrier along the electron transport system, a proton gradient is established across the thylakoid membrane; the potential energy of the gradient is used to form ATP (an energy package which the cell will use in its own processes). At the end of all these processes, the energy which plants need to create their own nutrition is ready for use.

These events, which we have tried to summarise as a chain reaction, are only the first half of the photosynthesis process. Energy is necessary for plants to produce nutrition. For this to be obtained, the other processes are fully completed, thanks to a specially planned "special fuel production plan."

The Dark Reactions

These processes, the second stage in photosynthesis, known as the Dark Reactions or Calvin Cycle, take place in the regions of the chloroplast known as "stroma." The energy-charged ATP and NADPH molecules produced by the light reactions are used to reduce carbondioxide to organic carbon. The end-product of the dark reactions is used as a starting material for other organic compounds needed by the cell.

It took scientists hundreds of years to understand the main lines of this chain reaction which we have summarized here. Organic carbons, which cannot be produced in any other manner in the world, have been produced by plants for millions of years. This molecule is the energy source for all living systems.

During the photosynthesis reactions, enzymes and other structures with different features and tasks work in complete cooperation. No matter what highly developed equipment it may have, no laboratory in the world can work with the capacity plants have. Whereas in plants all these processes take place in a tiny organ just one thousandth of a millimeter in size. The diverse formulae have been implemented for millions of years, with no confusion of all the variety of plants, no mistakes in the order of reactions, and no confusion in the quantities of basic materials used in photosynthesis.

The process of photosynthesis also has another aspect. The complicated processes outlined above lead plants at the end of photosynthesis to produce the glucose and oxygen essential to living things. These products made by plants are used by humans and animals as food. By means of these foods, they store energy in their cells and use it. By virtue of this system, all living things make use of the Sun's energy.

Like Everything Necessary for Photosynthesis,
Sunlight Has Also Been Specially Arranged

While all this is going on in the chemical factory, the features of the energy which will be used in the processes have been identified. When the photosynthesis process is looked at from this point of view, it will be realized in what fine detail the processes which take place have been planned, so that the features of light energy from the Sun may meet the energy requirement of the chloroplast to produce the correct chemical reactions.

In order to completely understand this fine balance, let us examine the functions and importance of sunlight in photosynthesis.

Was sunlight arranged specially for photosynthesis? Or are plants flexible enough to make use of any light that comes their way and initiate photosynthesis with it?

Plants are able to carry out photosynthesis thanks to the sensitivity of chlorophylls to light energy. The important point here is that chlorophyll substances use light of a particular wavelength. The sun rays have just the right wavelength needed by the chlorophyll. In other words, there is total harmony between sunlight and chlorophyll.

In his book, The Symbiotic Universe, the American astronomer George Greenstein has this to say about that flawless harmony:

Chlorophyll is the molecule that accomplishes photosyhthesis… 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.

A good analogy is that of 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 color – photosynthesis will not occur. As it turns out, the Sun's color is just right. (George Greenstein, The Symbiotic Universe, p.96)

In short, in order for photosynthesis to take place, all of the conditions have to be just right at that moment. It will be useful now to turn to another question that might come to mind. Could there have been any change over time in the order of the processes or the tasks carried out by the molecules?

One of the answers to this question that defenders of the theory of evolution, who claim that the sensitive balances in nature came about as the result of coincidences, is, "If there had been a different environment, plants would have initiated photosynthesis in that environment too, because living things would have adapted to it." But this is completely faulty logic. Because in order for plants to engage in photosynthesis they have to be in harmony at that moment with the light from the sun. George Greenstein, an astronomer who is also an evolutionist, reveals that this logic is faulty in this way:

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 color, take the place of chlorophyll? Remarkably enough the answer is no, for within broad limits all molecules absorb light of similar colors. The absorption of light is accomplished by the excitation of electrons in molecules to higher energy states, and the general scale of energy required to do this is 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 cannot 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.

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