We live in a world made from matter. Matter is made up of atoms and molecules that follow the laws of nature. All life is made up of atoms and molecules that are organized into cells. Our body has trillions of them. Many people know that the body needs chemicals like molecular oxygen (O2) and glucose (C6H12O6) for energy so it can do what it needs to do to survive. And some people know that the body needs chemicals like salt (NaCl) and water (H2O) to maintain the volume of its cells and the blood flow to its organs and tissues. But what most people do not know, and appreciate, is that, just like a car engine or an industrial plant, the chemical reactions the body uses in its metabolism often produce chemicals that, if allowed to accumulate, can be deadly. One of these toxic chemicals is acid (hydrogen ion (H+)). If the H+ ion level rises too high the body is said to be acidic and if it drops too low it is said to be alkaline. Either way, without the bodyís ability to keep its H+ ion level within a very narrow range, life as we know it would be impossible. The proof of this is that when our body loses control of its content of H+ ion, we die. But how does the body do it? Letís first look at what is needed to control something and then weíll see how our body makes sure its H+ ions play well with its many other chemicals so we can stay alive.
To be able to control something requires having at least three different parts all working together in harmony. The first thing you need is a sensor to detect what needs to be controlled. If you have no way of being aware of what needs to be controlled how can you control it? The sensor is like the reconnaissance team that an army sends out to check on the whereabouts and activities of its enemy. Without this information the army would be working in the dark. The second thing you need to control something is an integrator which interprets the information from the sensors, makes decisions about what needs to be done, and then sends out orders. If you donít understand the information from the sensors and canít make decisions about what should be done then what use are the sensors in the first place and how can you control something? The integrator is like army headquarters where the information from the reconnaissance team is analyzed, decisions are made about what needs to be done and orders are sent out. Without army headquarters there would be no coordinated action in the field. The third thing you need to control something is an effector which receives the orders from the integrator and does something. If you have a sensor to detect what needs to be controlled and an integrator to know what needs to be done, but not an effector to do it, then whatís the use of having the first two and how can anything be controlled? The effector is like the soldiers, who at the orders received from headquarters, go and do what needs to be done. Without soldiers there is, in effect, no army and the battle is already lost.
Hydrogen Ion (H+)
Hydrogen, the first element, consists of one positively charged proton and one negatively charged electron, and is the most abundant atom in the universe. Two hydrogen atoms joined together make a gas called molecular hydrogen (H2). In the body, where hydrogen atoms make up 10% by weight, they join with oxygen atoms to form water (H2O) and are present with carbon and oxygen atoms in glucose (C6H12O6). In addition, hydrogen atoms join with carbon, oxygen and nitrogen atoms to form proteins, the working chemicals of the body.
In some hydrogen containing compounds, like hydrochloric acid (HCl), where hydrogen atoms give up their electrons to chlorine atoms, the compound breaks up into positive hydrogen ions (H+) and negative chloride ions (Cl-). The same thing tends to happen with some of the hydrogen containing compounds in the body as well. In fact, even in pure water a very tiny amount of the H2O molecule splits up into positive hydrogen ions (H+) and negative hydroxyl ions (OH- ). The normal range for the level of H+ ion in the blood is 35-45 units. When the H+ ion level is outside this range the chemical reactions in the cells do not work as well and the body begins to malfunction and feels weak. The further the H+ ion level drops below, or rises above, the normal range, the more the body malfunctions and the weaker it becomes. In fact, H+ ion levels below 20 units or above 100 units are incompatible with life. So, one can see that keeping tight control of its H+ ion level is very important for proper body function and survival.
When the body breaks down certain proteins, and other chemicals, it releases H+ ions. The kidneys take these H+ ions, combines them with other chemicals, in a process called buffering, and releases them from the body in the urine. However, most of the H+ ions produced in the body (99%) comes from cellular respiration. Cellular respiration is the process by which the cell breaks down glucose (C6H12O6) with the help of molecular oxygen (O2) to get the energy it needs to live and function properly. This process results in the release of water (H2O) and carbon dioxide (CO2).
Most of the CO2 in the blood joins with H2O to become carbonic acid (H2CO3) because the red blood cells contain an enzyme called carbonic anhydrase which facilitates this reaction. In the blood, carbonic acid then breaks up into positive hydrogen ions (H+) and negative bicarbonate ions (HCO3-). So, the more CO2 the body produces from cellular respiration the more H+ ions form from carbonic acid and the more acid (H+ ion) is present in the blood. However, as noted above, the body must keep its H+ ion level between 35-45 units to work properly. Moreover, to allow the H+ ion level to fall below 20 units or rise above 100 units means certain death. So how does the body do it? Letís look at one of the main ways.
Control of H+ ions
Recall, the first thing you need to control something is a sensor that can detect what needs to be controlled. The body has chemical sensors (chemoreceptors) located in the main arteries that carry blood to the brain and also within the brain itself that can detect the H+ ion level. The exact nature of these chemoreceptors is as yet poorly understood. Recall, the second thing you need to control something is an integrator that can take the data it receives from the sensors, compare it to a standard, decide what needs to be done, and then send out messages to target organs that can do something. The data about the level of H+ ions is sent by nerve messages from the chemoreceptors to the respiratory center located in an area of the brainstem called the medulla. The respiratory center receives the information, analyzes it and then sends out nerve messages to the muscles of respiration. How the respiratory center “knows” what the H+ ion level should be so the body can live and function properly is at this time a mystery. Recall, the third and final thing you need to take control is an effector that can do something about the situation. The muscles of respiration respond to the messages from the respiratory center by making the lungs breathe air in and out. Breathing air in brings in fresh supplies of O2 and breathing air out releases the CO2 produced by cellular respiration. Moreover, from the foregoing it is evident that respiration not only affects how much O2 comes in and how much CO2 goes out, but also the blood level of H+ ion as well.
Anyone who has ever held his breath has experienced what it is like to try resist the respiratory centerís urgent messages to the muscles of respiration to “breathe now”. The longer you hold your breath the higher the CO2 and H+ level rises and the stronger the message for you to breathe. If the level of H+ ion level rises above the normal range of 35-45 units the respiratory center sends out messages telling the body to breathe in and out faster and deeper. This makes the body release more CO2 and as a result the H+ ion level drops back toward the normal range. Conversely, if the H+ ion level drops below the normal range of 35-45 units the respiratory center tells the body to breathe in and out slower and shallower. This makes the body release less CO2 and tends to raise the H+ ion level back toward normal.
The body must keep very strict control of its H+ ion level to live and function properly. It produces 99% of its H+ ions through cellular respiration which is how its cells obtain energy. This takes place because the breakdown of glucose in the presence of oxygen (O2) produces not only water (H2O) but also carbon dioxide (CO2) as well. With the help of an enzyme in the red blood cells CO2 becomes carbonic acid (H2CO3) which breaks up into ions of H+ and HCO3- (bicarbonate). The body also produces H+ ions when it breaks down proteins and other chemicals in the body. Although the kidneys do have a role to play, since 99% of the bodyís acid (H+ ion) production comes from cellular respiration it is the lungs that do most of the work when it comes to H+ ion control in the body. The body has sensors in its main arteries carrying blood to the brain and within the brain itself that can detect the H+ ion level. These sensors send the data about the H+ ion level to the respiratory center in the medulla. Based on the information from the sensors the respiratory center adjusts its messages to the lungs and regulates the respiratory pattern to make sure that the H+ ion level in the body remains within the normal range.
Points to Ponder
The way our body makes sure it has the right amount of hydrogen ion (H+) in its blood and tissues is not just as simple as having lungs and kidneys. To control its H+ ion level it requires, among other things, (1) chemoreceptors that can detect H+ ions and can pass on their information, (2) the respiratory center in the medulla to integrate the data from the sensors and know what needs to be done to keep the serum level of H+ ion in the normal range, and (3) the muscles of respiration to respond to the messages from the respiratory center by making the lungs breathe in and out at the right frequency and to the right degree. If any one of these three parts were to be missing, or not working properly, the whole system would fail and the body would die because of the loss of H+ ion control. Although people in respiratory failure usually have low levels of oxygen (hypoxia) they often die from having too much CO2 and H+ ions in the blood, a condition called respiratory acidosis. Each of the parts mentioned above that contributes to the sensor, the integrator, and the effector is needed to perform its vital function for body survival. Dr. Michael Behe has called a system where the absence of any one part renders it useless as being irreducibly complex. The system our body uses to control its H+ ion level demonstrates irreducible complexity.
One must then wonder how an irreducibly complex system with so many vital parts could have come into existence? Does it make sense that this system could have come about one step at a time? First the sensor, with no integrator or effector, or the integrator with no sensor or effector, or the effector with no sensor or integrator? The idea is totally absurd. They must have all come together as a system to perform a function to keep the body alive. And which system came first? The ones mentioned previously to control oxygen transport, blood glucose, water content, the levels of sodium, potassium and calcium, blood pressure, temperature and sexual function, or this one for H+ ion? Remember, without any one of these systems working properly, we, as individuals, or as a race, die. In addition to these there are other irreducibly complex systems each of which is absolutely vital for life. But if a system is irreducibly complex does that make it automatically capable of supporting life? If you think about it youíll realize that thereís one more piece of the puzzle thatís needed, a piece that goes beyond irreducible complexity, to enable these systems to keep us alive within the laws of nature.
People who work with hazardous materials, like acids, know that the amount and strength (concentration) of what they are using matters. Mixing the wrong type or amount of an acid with another chemical can be destructive and even deadly. In other words, when dealing with the forces of nature, real numbers have real consequences. The same applies to the body and how it survives in a world consisting of physical and chemical laws. When it comes to the blood level of H+ ions, not just any number will do. It has to be the right number so the chemical reactions in the cells can work right to allow the body to live and function properly. And depending how far out of range the H+ ion level is, the weaker the body and the more likelihood of death. Based on what we know about how the body actually works, our prehistoric ancestors would have had to have been able to keep their serum H+ ion levels between 35-45 units. This would have required them to have a properly working respiratory system and kidneys along with chemicals that combine with H+ ions to buffer it out of the blood. But what if the system in the body that controls H+ ions had been set differently? What if, instead, it had been set to keep the serum H+ ion level less than 20 units or more than 100 units? Then, all clinical experience tells us that our prehistoric ancestors could never have survived or reproduced.
Real numbers have real consequences when it comes to dealing with the laws of nature. Not just any amount of H+ ion will do. It has to be the right amount. Just because a system is irreducibly complex does not automatically mean that it will be able to function well enough to allow for life. Besides being irreducibly complex, systems that allow for life must also have a “natural survival capacity”. By this I mean that each system must give the organism the capacity to survive by taking into account the laws of nature. This usually involves having a knowledge of what is needed to keep the organism alive within the laws of nature and then being able to do what needs to be done. The system in the body that uses respiration, kidney function and chemical buffering seems to know what the serum H+ ion level should be and while we are healthy and functioning normally it keeps it there naturally. The same can be said for the many other control systems in the body, each of which is necessary for survival.
The laws of nature have put up many obstacles to prevent life from existing. Just as a car can die from not having enough gas for energy, or oil for seizing parts, or anti-freeze for engine overheating, so too, all physicians know that there are many different pathways to death. If you really want to begin to understand how life came into existence, you first have to understand how easily it can become non-existent. Did life really come about solely by random chemicals coming together to form cells, then simple organisms, and then complex ones like us? In other words, without “a mind at work” to make it happen?
Do you think that scientists working in research laboratories or production facilities just randomly let any types or amounts of acid be mixed with other chemicals to produce what they need? No, when it comes to the origin of life it seems to me that Science still has a lot of explaining to do!
Be sure to catch all of the articles in Dr. Glicksman's series, "Beyond Irreducible Complexity."
Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.
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