Introduction

A great many processes take place in your body to allow you to move just a single limb. These processes begin with the mental decision you make, becoming ever more complex in only a few instants. The series of reactions that begins with an urge arising in your brain may number in the billions, the countless enzymes in your body carry out every one of them. For even a very ordinary movement that you may want to perform, a vast number of processes occur, one after the other, inside each of your cells. Even while these thousands of reactions take place to enable that single movement, your brain carries on, and your heart beats, and the blood circulates at full speed. Foods entering your body are digested, your cells carry on their tasks, and all your organs continue to function in a flawless, systematic manner.
The activities in your cells never cease. You are not aware of them, nor do you have any control over them. All you can do is to gratefully accept the tasks they perform in order to keep you alive. The truth is, however, that in the same way that you have no control over these processes, neither do enzymes, other proteins, or the larger molecules that control them actually have any power to do anything. All these processes taking place in your body are under the control of Allah (God), and by depending on and placing your faith in this perfect system, you have actually submitted to Him. You are well aware that, apart from times of illness, none of your bodily functions will behave unexpectedly. The reason for your confidence is your trusting knowledge of the sublime might of Allah, Who created you so perfectly.
No one who claims to believe in coincidences can live out a calm, untroubled and peaceful existence by trusting in a DNA that began copying itself by chance, enzymes that first entered into reactions by happenstance, or a heart that began beating accidentally. The reason why people can remain unconcerned and untroubled is their total confidence that their body's systems are able to function free of error. Such individuals are well aware that these countless processes cannot be explained in terms of chance.
If a person knows how a single system in his body works—the enzyme system, for example—and can grasp the marvels that take place, he will better understand that nothing in the body can happen at random. He will realize that he is witnessing a miracle, bestowed upon him as a blessing. He will discover how molecules invisible to the naked eye work constantly to keep him alive, even though he is unaware of it, and how they have literally been programmed to do so. He will realize how they seem to make various decisions, behave economically, engage in a division of labor and act in a controlled manner—in short, how they behave like conscious entities. He will understand that it is Allah alone Who causes inanimate molecules to carry out actions requiring consciousness and how every molecule possessed by all living entities on Earth acts under Allah's inspiration.
Comprehending such things is itself a blessing, because anyone achieving a full understanding of this will trust in Allah throughout the course of his life. He will see that it is Allah Who keeps him alive, Who sets out his destiny and constantly bestows blessings upon him. He will know that He Who gives him life in this world, will also grant him life in the Hereafter, and will reward him with Paradise if He so wishes. He will turn to Allah, trust in Him and enjoy a peaceful life, free from all worries. That is one of the reasons why Allah produces perfect examples of His creative artistry. It is to be hoped that people will appreciate them and come to know Allah, our sublime Creator.

Allah is He Who raised up the heavens without any support—you can see that—and then established Himself firmly on the Throne. He made the Sun and Moon subservient, each running for a specified term. He directs the whole affair. He makes the signs clear so that hopefully you will be certain about the meeting with your Lord. (Surat ar-Ra‘d: 2)

Enzymes and Their Perfect Properties

If Allah so chose, it could take us decades to produce just a fleeting smile. We would have to wait for years to be able to eat, to think, or to move and speak. If Allah so chose, a whole lifetime even might not be enough for us to turn over a single page of one book, nor even lift a single finger for the purpose of doing so. Our bodily systems do not work at this slow pace, of course. We can smile whenever we wish, walk and run, think unrestrictedly, blink in an instant, and instantaneously begin to do everything we have planned. That is because Almighty Allah has blessed us with a system that permits our bodies, which He has created so perfectly, to perform all their functions at great speed. Enzymes, with their extraordinary structures, are one of the most important elements in this system's functioning.
In the chemical miracle known as enzymes, more than a hundred microscopic structures are combined in a three-dimensional form, whose details the human mind can grasp only with difficulty. Their function in the body is to accelerate all processes. Enzymes are essential in order for us to blink, move our hands, see, digest—in short, for us to pursue our lives. If the enzymes in your body were unable to function, you would perish.1 
Billions of the chemical devices known as enzymes are at work within you, even as you read these words. They initiate countless functions essential to your survival by performing countless processes at the same time. Unless the enzymes in your body initiated their particular events, it would be impossible for you to breathe, read these lines or move your eyes from one letter to another, let alone understand their meaning. You possess a nose, windpipe, lungs, and red blood cells to transport oxygen—everything, in short, that you need in order to breathe. But if the enzymes in your body did not function properly, you would be unable to draw breath.
By the mercy of Allah, we have very superior helpers in our bodies that, by His will, are in a constant state of activity. Again by the mercy of Allah, these all help to keep us alive. Were it not for them, just one of the millions of links in the chains that keep us alive would snap, and our lives would come to an end. In providing details concerning the miraculous structures and functions of enzymes, this website aims to exalt the glory of Allah. That a protein too small to be seen with the naked eye can determine whether a person lives or dies, is an example of Allah's matchless artistry. Allah demonstrates His dominion over humans by making the microscopic structures known as enzymes just means for this end. He reminds us of this important truth in a verse:

Say: "Who provides for you out of heaven and Earth? Who controls hearing and sight? Who brings forth the living from the dead and the dead from the living? Who directs the whole affair?" They will say, "Allah." Say, "So will you not guard against evil?" (Surah Yunus: 31)

The Structure of Enzymes

Every moment of our lives, every step we take or whenever we take a bite of anything, we are in constant need of enzymes. The events that occur in your body when you wish to take just one single step are truly amazing. Enzymes, the main agents in this molecular activity, are all miracles created by Allah.

When you wish to take just one single step, the events that take place in your body are truly amazing. Countless nerve cells inside the brain begin emitting tiny electrical impulses to set your legs in motion. By way of the spinal cord, these impulses are transmitted to other parts of the body, and thus to your legs. When this electrical signal from the brain reaches the legs, it causes the muscles in that region to contract and thus your legs begin to move. All these events take place almost simultaneously. A constant flow of information from your legs and from your other senses continues to reach the brain, very fast and without interruption. At the same time, the brain controls the commands it has issued for your leg muscles to move and also the movements that take place in their wake. The above paragraphs describe in a highly superficial manner the events that take place in order for us to take a single step. However, they all take place thanks to the presence of enzymes. Dr. Edward Howel, who has spent many years studying enzymes, summarizes their importance and effects:

Enzymes are substances that make life possible. They are needed for every chemical reaction that takes place in the human body. No mineral, vitamin, or hormone can do any work without enzymes. Our bodies, all of our organs, tissues, and cells, are run by metabolic enzymes. They are the manual workers that build our body from proteins, carbohydrates, and fats, just as construction workers build our homes. You may have all the raw materials with which to build, but without the workers (enzymes) you cannot even begin.2 

Enzymes are proteins that turn a cell into a highly developed miniature factory working within a highly ordered system. To date, over 2,000 enzymes have been identified..3 Working inside the arteries are 98 distinct enzymes, each with its particular job to do. No one has yet been able to determine how many enzymes control the heart, brain or liver..4 Enzymes initiate countless reactions within the cell, halt them when necessary, alter the shape of molecules, produce new combinations or eliminate ones that already exist. However, they themselves never suffer damage or undergo any changes. Having performed the needed tasks, they are ready to undertake new duties.
Enzymes function like catalysts: They accelerate chemical reactions without actually taking part in them. To better understand this concept, we need to understand just what catalysis is. In an environment where no enzymes are present, intense conditions—for example, extreme heat or highly acidic or alkaline conditions, and large amounts of what's known as activation energy are needed to break down a substance. In the laboratory, the production of activation energy depends on very critical conditions, of which the most important is high temperature. Yet inside the cell, thousands of reactions all take place at the same time and activation energy cannot be provided by way of body temperature, since the high temperatures needed would completely damage all other functions taking place within the cell. A cell exposed to high heat will lose all its cytoplasm and moreover, heat would break down the hydrogen bonds, have a negative impact on DNA replication and disable many other systems within the cell. It is therefore impossible for the activation energy constantly required in the cell to be provided through heat. Enzymes are therefore essential for reactions to take place inside living organisms without the need for a rise in temperature, because they reduce the amount of activation energy such reactions need. Catalysis is the name given to the process performed through the reduction in this energy. 5

Enzymes are catalysts that accelerate chemical reactions without actually taking part in them. In a matter of moments, they enable tasks that can be carried out only under intensive laboratory conditions and using enormous energy.

Enzymes perform catalysis by establishing temporary unions with the molecules they interact—but do not react—with. This temporary union weakens existing chemical bonds and allows new ones to form, allowing for a low level of energy to be used in order for the reaction to take place.6 In this way, enzymes accelerate the reactions they participate in by a factor of 1 million to 1 trillion times, in comparison to uncatalyzed reactions.7 In just one second, a single enzyme molecule may catalyze tens of thousands of identical molecules. Processes that chemists can perform only with the aid of high temperatures, reagents and special equipment, are undertaken so easily and regularly by enzymes, with no need for any acids, special apparatus, extreme temperatures or long periods of time. They carry out their functions flawlessly in a fraction of a second by producing a very low level of heat. These special proteins process fats, alter the structure of sugar, break down starch, form new nutrients, expel wastes and purify the blood. At the same time, they assist in delaying ageing, increase the resistance of the immune system, strengthen the memory and eliminate carbon dioxide from the lungs.8
Enzymes are like special assistants, constantly working to keep a person alive, and are essential to the working of all bodily functions. For that reason, the complex functions—and indeed, the very presence—of enzymes both represent major problems for the theory of evolution, which maintains that all of life's structures came into being in stages spontaneously, through a series of random genetic changes. But evolutionists' claim that life developed by chance starts from the assumption that the original structures were "simple" ones. However, modern medicine encounters new complexities regarding the human body with every passing day, further expanding the list of difficulties that evolutionists are unable to resolve. New discoveries constantly invalidate the 19th-century theory of evolution, which was invented in order to oppose the fact of creation. Aware of this significant fact, the Cambridge University evolutionists Malcolm Dixon and Edwin C. Webb provide the following definition of enzymes, one of the major stumbling blocks confronting the theory of evolution:

Enzymes enter reactions in various forms, and as a result, they give rise to new products. They process fats, break down starch and form new nutrients. Enzymes are special helpers that work to keep human beings alive.

The whole subject of the origin of enzymes, like that of the origin of life, which is essentially the same thing, bristles with difficulties. We may surely say of the advent of enzymes, as Hopkins said of the advent of life, that it was the most improbable and the most significant event in the history of the universe.9
What Dixon and Webb describe as "difficulties" are the complexities and perfections that evolution cannot account for. Evolution can offer no explanation for enzymes' mind-boggling complexity. Because the sole Creator of this sublime work is Allah, and He creates all things in a perfect manner. Frank Salisbury, an evolutionist and biologist, expresses this extraordinary complexity in enzymes—for which evolutionists are unable to account—thus:

Now we know that the cell itself is far more complex than we had imagined. It includes thousands of functioning enzymes, each one of them a complex machine itself. Furthermore, each enzyme comes into being in response to a gene, a strand of DNA. The information content of the gene—its complexity—must be as great as that of the enzyme it controls.10
This information is most significant. Enzymes are proteins that, by the will of Allah, form and also act under the control of genes. Therefore, genes themselves must have as at least as much complexity as enzymes. These words will serve as a reminder of the sophistication genes possess:

For example, we are told that the information content of the gene in its complexity must be as great as the enzyme it controls. Yet just one medium-sized protein will consist of about 300 amino acids! That protein was made by a DNA gene, which would have to have about 1,000 nucleotides in its chain. Since there are four kinds of nucleotides in a single DNA chain, one with 1,000 links could exist in 41000 different forms [Emphasis added]. That is 4 followed by a thousand zeros. Yet all this complexity is required to make the simplest living creature. 11 

Evolutionists claim that every structure in any living organism came into being as the result of long, slow stages and formed by chance by way of various mechanisms. (For more details on this subject, see Harun Yahya, Darwinism Refuted.) But the fact is that mutation and natural selection, which evolutionists propose as evolutionary agents, actually provide no evolutionary properties at all. No organ in any living thing has ever been observed to "evolve" by changing and assuming a form that could be of benefit to the organism as a whole. In addition, recent advances in medicine, biology and microbiology have revealed that any change in the protein or genes of an organism will only result in breakages, impairments and serious damage to its genetic information.
It is impossible for any gene or protein to turn into some other gene or protein with a completely different function. Evolutionists claim that the first protein was formed by chance under totally uncontrolled conditions, but they have never been able to produce one in the laboratory. It is unequivocally impossible for such a complex structure—which eminent scientists have been unable to reproduce using modern-day technology in state-of-the-art laboratories—to have come into existence spontaneously through random accidents.
Enzymes are all proteins, complex structures formed by way of extraordinary information contained in genes that themselves cannot have come into being by chance, and which function, at Allah's choosing, under the control of that gene. It is therefore impossible for them to have come into existence in stages, since the functions that enzymes perform are too precise, and the information that genes contain is so enormous. Despite being an evolutionist, Sir Fred Hoyle, the Cambridge University mathematician and astronomer, summarized the fact that enzymes cannot come into being by chance:

If there were a basic principle of matter which somehow drove organic systems towards life, its existence should easily be demonstrable in the laboratory. One could, for instance, take a swimming bath to represent the primordial soup. Fill it with any chemicals of a non-biological nature you please. Pump any gases over it, or through it, you please, and shine any kind of radiation on it that takes your fancy. Let the experiment proceed for a year and see how many of those 2,000 enzymes have appeared in the bath. I will give the answer, and so save the time and trouble and expense of actually doing the experiment. You would find nothing at all, except possibly for a tarry sludge composed of amino acids and other simple organic chemicals. How can I be so confident of this statement? Well, if it were otherwise, the experiment would long since have been done and would be well-known and famous throughout the world. The cost of it would be trivial compared to the cost of landing a man on the Moon.12

Even if evolutionists possessed a great many more conditions than those Hoyle refers to; even if they ran such an experiment in as many laboratories as they wished; even if they added to the experiment all the existing organic substances, all the gasses and chemicals they could; even if they exposed them to whatever external influences they liked; even if they added as many amino acids and protein building blocks as they wanted; and then waited for centuries alongside the beaker or retort into which they placed all these substances, never will they be able to produce a single enzyme produced in a living thing. Evolutionists have not the slightest piece of evidence to offer as proof for the formation of a single protein.
We need to bear this constantly in mind as we examine the subject of proteins. Because the existence of one single enzyme is sufficient to do away with the nonsense of evolution—as well as being major proof that constantly displays the boundless might and power of Allah. Enzymes take part in almost all an organism's chemical reactions, speeding them in an extraordinary manner. But again, they emerge from the reaction in the same state as they went into it—in other words, they remain unaltered. Once the reaction has taken place, newly formed molecules separate from the enzyme, and the enzyme continues on its way, ready to enter into still other reactions.

*Let evolutionists, who believe in the creative power of chance, take an enormous barrel. Let them place in it whatever substances they think will be needed to produce a living cell. Then let them warm the barrel, chill it or let lightning strike it. Let them stand guard over the mixture for billions or even trillions of years, passing their task down from one generation to the next. Let them leave nothing to chance, watching over the mixture at every moment. Let them be free to employ whatever conditions they think are necessary for life to emerge . . .

They will still be unable to extract a single cell from their barrel. They will be unable to produce a horse, butterfly, flower, duck, cherry, lemon, owl or ant. No matter what they do, they will be unable to produce scientists who examine themselves under the microscope, human beings who think, reason, make judgments, feel excitement, rejoice or grieve.

This feature is very important, because in this way, an enzyme is able to enter into countless reactions inside the cell and is able to keep the entire organism alive. In this way, hundreds of thousands of reactions take place constantly every minute, inside every cell.13 

The folded polypeptide chain structure of a three-dimensional enzyme molecule

Every one of the 2,000 or so different enzymes in the human body is able to catalyze a specific chemical reaction. Understandably, cells with different functions have different kinds of enzymes. Cells work only with those enzymes that will carry out the required reactions. Therefore, the specific enzymes any cell produces are an important element in identifying that cell's actions and functions.
Fred Hoyle made the following calculation regarding the astonishing power of enzymes:

The probability of forming the 2,000 or so enzymes needed by a cell lies in the realm of 1 in 1040,000. This makes the conceptual leap from even the most complex ‘soup' to the simplest cell in the time available (that is about 500 million years) so dramatic that it requires some suspension of rationality in order to accept it.14

Enzymes combine with various chemicals, impel them into amazingly fast reactions, and then depart. A brand new product now emerges. This special ability of enzymes allows life to continue.

All the structures of the living things on Earth have different levels of complexity. And the enormous variety of structures they possess reveal only a flawless creation. Living things possess molecular "handymen" that divide tasks among themselves, constantly communicate with one another, act dependently on each other and carry out true miracles of efficiency. It is impossible for them to decide beforehand how many reactions they will enter into, to then act in a conscious manner, know which cell to operate in, determine what processes to accelerate and by how much. Yet although this is indeed impossible, enzymes never make a mistake, because all their actions are inspired.
It is Allah Who constantly inspires them with what they have to do. And it is He Who continually creates them. In the same way that Allah gives a human being both a body and a soul, and creates him with all his perfect organs and senses, He also creates with the same perfection the extraordinary events that take place within the cell. For that reason, the enzyme system functions perfectly, just like the other systems inside the cell. No power apart from Allah's can create these, and Allah reveals this fact in one verse: :

Is it other than the religion of Allah that you desire, when everything in the heavens and Earth, willingly or unwillingly, submits to Him and to Him you will be returned? (Surah Al ‘Imran: 83)

Flawless Harmony Between Enzymes and the Human Body

The Genes that Encode Enzymes

Enzymes are all proteins, and therefore have a protein structure, possessing the three-dimensional structural features unique to proteins. For that reason they are easily able to attach to other molecules and take part in reactions.
Although amino acids are the building blocks of proteins, what gives a protein—and thus, an enzyme—its characteristic feature is the order and number of the amino acids and the so-called peptide bonds that connect two amino acids together.15 Which reactions an individual enzyme will affect, as well as their speed, are determined by the features and arrangement of the amino acids. But what determines which amino acids an enzyme should consist of?
Imagine an enzyme consisting of 100 amino acids. Since there are 20 different kinds of amino acids in living organisms, these hundred amino acids can be arranged in 10020 different ways. Yet only one of all these sequences will constitute the proper enzyme. Here it is the genes that, by the will of Allah, determine the correct sequence. As already pointed out, enzymes are arranged and controlled by genes. All proteins, whether within the structure of the cell or those exhibiting enzyme activity, are synthesized by genes, which tell the enzymes which duties they are to assume. In other words, their encoded instructions determines which reactions enzymes must enter into. In light of this information, enzymes head for the specific molecules they will launch into reactions.

Enzymes are regulated and controlled by genes. Genes inform the enzymes they produce of their duties—in other words they encode their instructions. Therefore, enzymes must be at least as complex as the information encoded in the genes. This fact clearly shows that evolutionists, who are unable to account for the existence of genes in the first place, also have no explanation to offer on the subject of enzymes.

Here, it will be useful to recall that neither enzymes nor the genes that encode their behavior are conscious entities. It is impossible for genes, much less the enzymes that receive data from them, to act of their own accord, to think about making any decision, or to produce their own special codes. Made up of protein and fats, they are not conscious entities and have no way of knowing what a human being needs to live, how to intervene in a reaction, nor what purpose that reaction is to serve. They cannot have acquired their complex structure, nor accelerate thousands of reactions a second as the result of chance. Yet although lacking consciousness, they perform miraculous processes in every cell because they have submitted to Allah, their Creator. They obey Him, and act in the light of His inspiration. Keep this in mind as you read these pages.
Genes encode both the proteins inside the cell and also those that serve as enzymes. But what determines that a protein they manufacture will serve as an enzyme? In other words, what determines the enzyme's ability to become involved in chemical reactions and accelerating them millions of times?
In strictly chemical terms, this is explained by characteristics in the chemical structure of the amino acids. Amino acids consist of an amino group (-NH2) attached to a single carbon atom, hydrogen, a carboxyl group (-COOH) and varying side chains (-R) that can be composed of different molecules. What distinguishes one amino acid from another are its size, shape, electrical charge, water affinity and activity of the side chains it carries. The characteristic of the amino acids constituting enzymes is that they interact with one another, as a result of which they acquire a three-dimensional form that allows the chain to bend and curve.

Enzymes are proteins with a tertiary structure. The amino acids making up the protein bend and fold to give each enzyme its particular form. Enzymes' tasks are determined as a result of the bends and folds in these tertiary structures.

How these amino acids are arranged gives the resulting proteins various properties. Accordingly, proteins assume what are called primary, secondary, tertiary and quaternary structures. In the primary structure, a flat polypeptide chain operates. In the secondary structure, the protein acquires a three-dimensional shape and its functions are determined according to its particular three-dimensional shape. The polypeptide chains are packed in the same horizontal plane and give the protein a helix shape. In a tertiary structure, that helix structure in question assumes a special shape by becoming bent. In a quaternary structure, all the emerging subunits come together, giving rise to a more complex structure.
Enzymes are proteins with a three-dimensional tertiary structure. By folding and bending, the amino acids making up their proteins endow enzymes with a special shape that's of the greatest importance, because they enable a great many life-giving functions to take place. Their three-dimensional tertiary structure permits polypeptide chains to fold over, knot together or wind around themselves, and permits enzymes themselves to vary greatly.

An enzyme's three-dimensional form determines whether it is involved in blood coagulation or digestion. This fact is just one of the astonishing details in the perfect structures created by Allah.

The tertiary structure endows an enzyme with still other properties. The primary structure of proteins consists solely of covalent bonds—a form of chemical bonding formed by the sharing of electrons between atoms. These powerful bonds decrease ever further in subsequent structures, until in a quaternary structure there are no covalent bonds at all. In a tertiary structure, the covalent bonds that form enzymes appear only in regions between adjacent chains. This enables only the surface regions of the enzyme to bond tightly to one another in order to grasp molecules and let them enter into reactions. The power of these bonds keeps them from breaking. It is only the enzyme's "shape" that determines whether it's a blood-clotting enzyme or one that is involved in digestion. But how did any enzyme come to possess its highly specialized form? Out of millions of possibilities, how is it that enzymes always assume the correct shape? If evolutionists maintain that the first enzyme or the first gene that formed it appeared on Earth spontaneously and by chance, then they are forced to explain the development of all of an enzyme's complex details, as well as the three-dimensional form that determines its properties. In addition, they must account for the special abilities of the genes responsible for encoding this. If the special form in the very first enzyme came about by coincidence, through trial and error—impossible, though assuming that it actually did happen—then a simple calculation reveals that for a single enzyme molecule consisting of 100 amino acids to test out all the different possible permutations would take 20 billion years—a much greater time frame than the age of the universe itself!16
And that probability emerges only if we imagine that amino acids are consciously able to employ the method of trial and error. Yet it is completely impossible for amino acids to combine without any conscious method, to form a small enzyme molecule consisting of 100 amino acids. Therefore, evolutionists are totally unable to account for the formation of an enzyme and its particular three-dimensional form. Duane T. Gish, director of the Institute of Creation Research, explains this impossibility:

One hundred amino acids of 20 different kinds can be arranged in 20¹⁰⁰ (10¹³⁰) different ways. If 10¹¹ of these could function as the primitive enzyme, and if a billion trillion 10²¹ of the various protein molecules of 100 amino acids formed each second for five billion years (approximately 1017 seconds) the chance of getting a single molecule of one of the required sequences is 10¹³⁰/10²¹x10¹⁷x10¹¹, or only one chance out of 10⁸¹. This is, for all practical purposes, equal to zero probability.17

As this example shows, it's impossible for amino acids to come together by chance in the correct sequence to form an enzyme. Therefore, any one enzyme's existence and functions totally eliminate the idea of gradual evolution.

How Does an Enzyme Determine the Reaction It Will Affect?

In the structure of the amino acids that make up the enzyme, the various side chains accumulate in one region of the enzyme to form a three-dimensional structure known as the "active site." This is where the enzyme binds to other substances during a reaction.

The enzyme's active site combines with a substance known as the substrate. The substrate on which every enzyme acts is unique to that enzyme.

That substance, on which the enzyme will act, is known as the substrate. The active site of any particular enzyme can fit into the substrate of only the molecule it will affect. It is impossible for this substrate to bind to the active site of any other enzyme. The enzymes' active sites possess two important components. One of them recognizes the substrate and the other, upon binding to the substrate, is responsible for catalyzing the reaction.
Within the body, in fact, the enzyme and the substrate are two structures that are entirely foreign to one another. Although they have never seen each other, the moment they meet inside a volume many billions of times larger than themselves, they can distinguish each another from among a very large number of molecules and bind together. One of the main features that permits this bonding to occur is the enzyme's tertiary structure. The molecule that bends and assumes its own special three-dimensional shape possesses a gap of highly complex geometry into which the substrate will fit perfectly. The active site and the substrate fit together just like a lock and a key. In the absence of the key—the enzyme, in other words—the door can be opened only by forcing it, which inside the human body is impossible because of the high level of energy that would be required.

*The enzyme and substrate fit each other like a lock and key. In the same way that a single key opens a single door, so specific enzymes will fit only specific substrates.

In the same way that any single lock can only open a single door, specific enzymes are compatible only with specific substrates. This compatibility also takes effect at an impressive speed—so great that an enzyme sometimes binds to 300 substrates, in a specific sequence, in just one second. It converts those substances into different molecules, then breaks away. This process will continue uninterruptedly throughout your life.
Within the cell, the numbers of enzymes and substrates are actually quite small. That being so, how are the enzymes and the substrates matching them able to locate one another? If the cell's inside structure were static, it might never be possible for enzymes and substrates to bond together, despite their both being in the same environment. But no such problem exists, since the contents of the cell is in a constant state of motion. Various movements caused by heat occur at the molecular level; and molecules inside the cell are moving constantly from one place to another. The interconnected atoms that compose these molecules vibrate in situ. Proteins, which are larger molecules, revolve around their own axes some million times a second. This astonishing motion leads to all molecules within the cell constantly colliding with one another.
*Enzymes carry out countless reactions in the space of a second and produce new products. A truly amazing order operates within the enzyme system for this purpose. It is Almighty Allah, the Creator of all things, Who maintains this order at every moment and constantly preserves it.
 As a result of these collisions around 500,000 times a second, the active site of an enzyme is subjected to a bombardment by the relevant substrate molecules, despite their low numbers inside the cell. As a result of this bombardment, the substrate fits into the surface of the relevant enzyme and these molecules immediately assume the form of an enzyme-substrate molecule, now ready to enter into a reaction.18
Enzymes bind to any substrate they meet—whether compatible with them or not—by means of very weak hydrogen bonds. The structure of the hydrogen bonds give the enzyme and substrate their own unique shape and property. In addition to the hydrogen bonds, however, when the enzyme encounters the correct substrate and the two join together, new bonds form—including such chemical interactions as van der Waals force, electrostatic force and hydrophobic bonds. Thanks to such bonds, the link between the enzyme and substrate is strengthened, reducing the possibility of their separating.

The substrate that binds to the enzyme's active site exactly matches the three-dimensional form of the region it settles on. This perfect artistry belongs to Allah, Lord of the worlds.

If one of the two colliding molecules is not a substrate of the other, then the conditions are rather different. Two molecules form a weak bond between their more or less compatible surfaces, as if they were attempting to join together. The energy released is insignificant. The moment the enzyme recognizes that it does not have the key to open the substrate in question, it breaks these weak bonds and rapidly moves away. This is a most important precaution, preventing incorrect or unwanted bonds from forming between incompatible molecules.19
Enzymes and substrates that fit together also take precautions. Recent evidence indicates that when an enzyme interacts with the substrate, it may change shape slightly, much as a glove that changes shape somehow to fit the hand it covers.20
The structures we have described here as seemingly conscious entities are simply two molecules, with no ability to see, hear, communicate or make any decisions. The abilities they appear to display successfully inside the human body actually belong to Allah, Who controls and supervises them at every moment. No substrate can bind to an enzyme unless Allah so wishes it, nor perform the processes that permit a person's vital functions. An enzyme only locates the component necessary for it, matches it and tries various ways of combining with it—exhibiting seemingly rational, conscious behavior under the direction of Allah. The way that inanimate molecules display such behavior is a great miracle. Those unable or unwilling to see the evident miracle here look elsewhere by ascribing some extraordinary intelligence to molecules themselves, to atoms, or even to chance itself. In fact, however, all scientific endeavor declares that Allah is the sole Lord of Earth, the sole mighty and sublime Creator. Allah creates from nothing and manifests His own omniscience in the entities He chooses.

Yes, indeed! Everyone in the heavens and everyone on the Earth belongs to Allah. Those who call on something other than Allah are not really following their partner-deities. They are only following conjecture. They are only guessing. (Surah Yunus: 66)

What is in the heavens and in the Earth belongs to Allah. Allah suffices as a Guardian. Humanity! If He wanted, He could remove you altogether, and produce others instead. Allah certainly has the power to do that. (Surat an-Nisa', 132-133)

What if the key did not fit the lock? What if the enzyme were in the correct location, but did not match the substrate? What if the enzyme reached the site of the reaction needing to be accelerated, but then passed by the relevant molecules? If because of just such a structural incompatibility, the enzymes necessary to coagulate the blood flowing from an open wound failed to perform their duties, then the blood would never be able to clot. No reactions essential for cell renewal could ever occur, nor could vital processes be maintained at the same rate and in the same order. For an enzyme to do what is expected of it, it has to recognize the substance—in other words, the substrate—on which it has to act and to match it completely. By the will of Allah, there is never any such problem in this regard in the living body. Every enzyme recognizes without difficulty the substrate it must react with and, since it acts under the inspiration of Allah, never makes a mistake in carrying out the process it needs to perform. The key always fits the lock; the needed reaction always takes place.

All this happens inside a cell with a diameter of just 0.01 millimeter. (A cell is between 10 and 100 microns in size.) Compatible molecules and the chemical bonds between them are all contained in a space just 0.01 mm in size. Three-dimensional structures, molecules attached to one another, cavities with specific geometries on the molecular surface, and other molecules with the geometric shapes to fit those cavities are all contained inside that area. Molecules that are compatible with one another—that are evidently aware of one another and can  determine each other's requirements, that are capable of setting aside time, that never tire and are easily able to identify any molecule they encounter—all work within that environment. And recall that environment is only a cell less than 100 microns in diameter, in which electrons are in constant motion. A system inside the cell gives rise to a perfection exceeding all human capabilities, intelligence and knowledge, one that mankind can scarcely ever equal, which never goes wrong or makes a mistake—a totally conscious system.

That consciousness does not belong to the cell itself, of course. It cannot belong to molecules, mere collections of atoms that are unaware of one another inside the cell, nor to unconscious enzymes that come and go among these molecules. Neither does this consciousness belong to the human body that harbors all of these, nor to the human brain. The source of this consciousness is Allah, the Omniscient and Almighty, and He manifests His infinite might and intelligence in everything that He creates. He is manifest in the boundless universe as well as in enzymes just a hundredth of a millimeter in size. Great or small, it makes no difference—there is the same complexity, perfection and artistry in all, because Allah creates them all with His boundless knowledge.
Allah tells us this in a verse:

Don't they see that Allah, Who created the heavens and Earth, has the power to create the like of them, and has appointed fixed terms for them of which there is no doubt? But the wrongdoers still spurn anything but disbelief. (Surat al-Isra': 99)