The right chemistry: science fiction, science fact

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The plot of The Andromeda Strain is based on the doctor’s understanding of the chemistry of blood, a very complex liquid.

Author of the article:

Joe Schwarcz • • Especially for the Montreal Gazette

Release date:

January 01, 2021 • • January 1, 2021 • • Read for 4 minutes • • Join the conversation A bag of blood is shown in a clinic in Montreal. A bag of blood is shown in a clinic in Montreal. “Blood is actually a ‘buffered’ solution, which means that it contains components that can react with excess base or acid to restore normal pH,” writes Joe Schwarcz. Photo by Ryan Remiorz /.The Canadian press

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Long before COVID-19 and before terrifying movie audiences with carnivorous velociraptors in Jurassic Park, Michael Crichton terrified readers with the story of a murderous alien microbe. In his 1969 novel, The Andromeda Strain, a satellite returns to Earth contaminated with a microbe that quickly kills everyone near the city it lands in except the drunken city and a crying baby. Why did they survive? Everything has to do with acidosis and alkalosis. Time for a simple physiology.

Blood is a very complex fluid that contains numerous components, including various acids and bases. The acidity of a solution is described using the pH scale, on which 7 is neutral, below 7 means acidity and above 7 means that the solution is basic or alkaline. Blood pH is critical to maintaining good health, and disasters occur when the pH is outside the normal range of 7.35 to 7.45. Acidosis can cause weakness, nausea, and confusion, while alkalosis is associated with irritability, muscle twitching, and convulsions. In extreme cases, both conditions can be fatal.

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The human body is a remarkable machine. Blood is actually a “buffered” solution, meaning it contains components that can react with excess base or acid to restore normal pH. Carbon dioxide, which is produced by the metabolism of food, dissolves in the blood to form carbonic acid, which can neutralize excess bases. The bicarbonate ion, which is also present in the blood, immediately takes care of excess acid.

The level of carbon dioxide in the blood can also be adjusted by our breathing rate. When the pH of the blood drops, which actually means that the blood has become more acidic, we breathe faster, exhaling carbon dioxide and thereby reducing the acidity. When the pH rises, breathing is inhibited, less carbon dioxide is exhaled, and the pH returns to normal. Then there is a backup system. The kidneys can regulate the pH of the blood by excreting or holding back acid.

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This regulatory system is very effective and can address most, but not all, challenges. Conditions that affect breathing, such as pneumonia, violation of the respiratory center of the brain, or overdose of morphine, can lead to “airway acidosis”. Uncontrolled diabetes, kidney failure, and starvation can lead to a decrease in blood pH and cause “metabolic acidosis”. This can also happen from an alcohol overdose or antifreeze poisoning, as both substances are metabolized to acidic compounds.

Respiratory alkalosis is usually caused by excessive loss of carbon dioxide due to hyperventilation. Therefore, hysteria or panic attacks can have physical consequences and can be treated by inhaling a paper bag. The exhaled carbon dioxide is inhaled again and lowers the pH value! Metabolic alkalosis can be caused by the loss of hydrochloric acid from the stomach due to prolonged vomiting, kidney disease, or excessive intake of antacids.

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These ideas were elegantly presented to the public in The Andromeda Strain. Michael Crichton was a doctor with a solid scientific background whom he wove a genius plot with. It appears that the invading microbe can only multiply effectively in human blood that has just the right pH. And guess what pH our invading virus prefers? That’s right, 7.4, the pH of normal blood.

Why did the baby survive? Because he cried and screamed with all his might and exhaled a lot of carbon dioxide. This, as we have seen, increases the pH. The drunk, on the other hand, had run out of wine and only had to drink sterno! This is the small can of gelled fuel that warms up many a buffet from below with an almost invisible blue flame. The flammable component is methanol, also known as wood alcohol. In the liver, methanol is converted into formic acid. This acidifies the blood, changes the pH and causes havoc. Drink enough methanol and it will kill you. Our friendly drunk was lucky enough to indulge himself just enough to slightly alter the pH of his blood. enough to destroy the deadly microbe, but not enough to kill it. A bit of a stretch, but at least rooted in real physiology.

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However, Crichton goes deep into science fiction by describing that the microbe does not contain DNA, RNA or proteins and exists through its ability to convert energy into matter. Eventually, Andromeda mutates into a benign form, quite an achievement without containing any genetic material. There’s an interesting twist. Before the microbe becomes benign, it mutates into a form that lives from eating plastic. We could use such a microbe today to clear the oceans of such debris.

In 1971, The Andromeda Strain was made into a film that was pretty close to the plot of the novel except for the end. In the film, clouds were sown to precipitate rain and wash Andromeda into the alkaline waters of the oceans. The pH of seawater is around 8.1 due to the leaching of basic calcium carbonate from mussels, corals, and limestone deposits and would indeed be fatal to a microbe that can only survive in the 7.4 pH range. Enjoy the book and watch the movie!

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Joe Schwarcz is Director of the Office for Science & Society at McGill University (mcgill.ca/oss). He moderates the Dr. Joe Show every Sunday from 3 p.m. to 4 p.m. on CJAD Radio 800 AM

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