Could A Human Cell Get Hotter Than 200 Degrees Via Its Own Chemical Reactions?

[LisaL]

Question inspired by the second picture from this article http://thugviral.com/20-scary-photos-that-are-real-but-you-will-wish-they-werent/

[CraigD]

“Could A Human Cell Get Hotter Than 200 Degrees Via Its Own Chemical Reactions?”

I think you’re asking “can the cells in a human body produce a temperature greater than 200 C via a chemical reaction using only the compounds in it?”

 

My guess is that, ordinarily, they can’t. In any case, such a high temperature would destroy – kill – most biological cells, so regardless of where the reactants come from, those from cells would no longer be part of structurally intact cells, but just animal-derived molecules.

 

This is because biological cells contain too little oxygen. Fat (triglyceride) has a simplified chemical formula like C₅₅H₉₈O₆, protein like N₂C₂H₈O₂. From an energy-producing perspective, they’re essentially hydrocarbons, so follow the equation

C_aH_2b +cO₂ -> aCO₂ +bH₂O + energy

releases nearly all their possible chemical energy. For this to happen, a lot of external oxygen – about 2.6 times the mass of the fuel, in the case of fat – must be added. Fortunately (or unfortunately, as the case may be), we’re usually surrounded by oxygen-rich air, so reactions like this can be produced as easily as lighting a candle.

 

Give a supply of oxygen, there’s a lot of chemical energy in fat – about 38 MJ/kg – and about half as much per unit mass – 16.8 MJ/kg – in protein. By comparison, gasoline has about 44.4 MJ/kg, not much more than fat.

 

(sources: http://hypertextbook.com/facts/2004/PingZhang.shtml, http://hypertextbook.com/facts/2003/DavidDukhan.shtml, http://en.wikipedia.org/wiki/Combustion#Stoichiometric_combustion_of_a_hydrocarbon_in_oxygen)

 

As we’re essentially ambulatory containers of medium-grade fuel, an animal body, human or otherwise, is potentially very combustible, once one gets around the barrier that the highest energy density fuel – fat – is neatly encapsulated in a wet volume enclosed I in a tough skin outer container.

 

In cases like the awful image of almost completely burned human body in a bathroom in the linked-to thugviral.com collection,

 

what appears to have happened is that something easily ignited, such as clothing or furniture, was ignited and burned long and hot enough to breach the victims skin and ignite the body’s fat. This then burned, consuming almost the entire body – in this case, it appears, leaving just one foot and a partial leg unconsumed. Because of the similarity to a burning candle, this is known as “the wick effect”.

 

This scenario has been confirmed using pig carcasses – the Wikipedia article “Spontaneous human combustion” has a summary of the subject. Despite the common inclusion of “spontaneous” in the term, most scientists believe this kind of burning doesn’t mysteriously start itself, but is started by an ordinary fire near the victim.

[HydrogenBond]

The combustion processes within living cells, is designed to create intermediate products like ATP which is then used as energy source. The formation of ATP is endothermic and takes away heat/energy from the combustion area; metabolism. 

 

On the other hand, if you ever composted grass clippings, for example, the decomposition reactions can get very hot. Dead is different from living.

 

Certain natural oils, like linseed oil and tung oil can spontaneously combust. These oils are often applied with rags to finish furniture and treat wood. The cans have warnings that the rag can burst into flames and one needs to store these in metal containers and not just put it in the trash. The living may not spontaneously combust but decomposition is a wild card. 

[CraigD]

The living may not spontaneously combust but decomposition is a wild card.

I agree that living organisms don’t spontaneously combust, but think it’s a false dichotomy to distinguish “living” from “decomposition”, because the main decomposition processes are simply due to metabolism by small living organisms. For example, compost from grass clippings and other yard, garden, and household waste, or other common sources, is the end product primarily of bacteria, fungi, and protozoa.

 

The combustion processes within living cells, is designed to create intermediate products like ATP which is then used as energy source. The formation of ATP is endothermic and takes away heat/energy from the combustion area; metabolism.

Though people commonly refer informally to biological processes as “burning”, in my experience the term “combustion” usually refers only to non-biological exothermic reactions involving oxygen combining with “fuel” elements, such as

2H₂ + O₂ -> 2(H₂O)

 

ATP (C₁₀H₁₆N₅O₁₃P₃) is technically a coenzyme – it helps in biological reactions, while not being the main source of chemical energy in them - but along with the similar ADP ((C₁₀H₁₆N₅O₁₃P₂)) is so important and ubiquitous that it can be informally thought of as a kind of biological “fuel”. ATP is biologically synthesized in many ways, but I wouldn’t describe them as “endothermic” – “heat taking” – because they are chemical reactions that produce heat – exothermic reactions. ATP-ADP cycling reactions are complicated – and example of a major one is glycolysis. It looks fairly simple when just the beginning and end products are considered, but has lots of intermediate steps.

 

The term metabolism refers to practically all kinds of important biological reactions, not just ones that convert ATP to ADP producing mechanical energy used by cells.

[HydrogenBond]

Combustion is normally done in air, while metabolism is done within water. Water is one way to quench the fire of combustion because among other reasons, water is one of the main products of the combustion. An excess of product will inhibit the forward reaction. Metabolism is a combustion that is limited by having to occur within a vast surplus of final product.

 

Fire fighters also use water to cool a fire, so the heat of the combustion, can't cause further combustion via radiation and activation energy. Metabolism has its own containment coolant, so the combustion stays localized. Life only needed to evolve ways to catalyze a process that was already self limiting. 

 

As CraigD pointed out the metabolic combustion is not done in one step, but has to be done in baby steps because the water is very inhibiting. The formation of ATP, by being endothermic, spread out the heat away from the metabolic furnace. This indirectly inhibits chain reaction combustion similar to the fire fighter spraying water on the fire to keep it cooler.  

Edited March 24, 2015 by HydrogenBond

[CraigD]

Metabolism is a combustion that is limited by having to occur within a vast surplus of final product [such as water].

I think it’s a bad idea to use biological and chemical terms so weirdly, HBond. :naughty: It’s confusing, and can lead to wrong intuitions and conclusions.

 

I think this GSU hyperphysics entry does a good job of describing the similarity, but distinctness, of metabolism and “actual combustion”:

Metabolism is a generic term for all the chemical reactions that break down or "burn" food to provide energy for the operation of an organism. The word "burn" is used advisedly, because the energy yield from a food in the human metabolic process is comparable to the energy obtained by actual combustion. The energy available from a food is commonly stated in dietary Calories, and the Calorie rating of a food may actually be obtained by burning it in a pure oxygen atmosphere in a calorimeter to measure the energy yield from this combustion.

The key takeaway from this is that metabolism is comparable to combustion, but not the same as it.

 

Metabolic processes aren’t fires partially quenched in water, nor does water control metabolic reactions in the way that hosing water onto a fire controls its burning. Biological processes are more varied and complicated than combining fuel with oxygen to produce combustion, not because they must be because they occur in water, but because these complicated processes work better than ones like simple combustion.

[HydrogenBond]

Metabolism is a special case of combustion, with both reacting organics and oxygen and both leading to water and CO2. Both can be starved of oxygen and still react. The overall topic is about spontaneous human combustion, using the special case of metabolism; the weaker combustion changes into the other. 

 

This discussion also brings up why water is the only solvent that can support life. Other solvents have been speculated, but none have been proven to support life.

 

One reason is, the solvent of earth life; water, is a product of metabolic combustion. If we used any other solvent to create a parallel these solvents would need to be a final product of metabolic combustion or else the life form would eat its solvent for food.

 

The problem with other solvent is, as final products of metabolism, they all will still contain energy. If the lifeforms evolves to make use of that, extra energy, the solvent will become a fuel source. This could lead to spontaneous combustion. Water is the most stable of the solvents, under fire, and can't be modified further by metabolic combustion. 

 

For example, say life evolved that used a solvent, like ethanol. The metabolic combustion would need a failsafe, that only allow it to  burn food down to alcohol, or it will start to self digest its solvent. This tipping point could lead to a runaway combustion where it burst into flames; a spark that will change metabolic combustion into combustion.  With water, the metabolism hits a wall and can evolve no further, making life stable. Water can put out the flames of combustion. 

 

All the speculated solvents could lead to spontaneous life combustion until water is reached. Biology could benefit by a physical chemical approach because it can simply the complex; function before form. 

Edited March 25, 2015 by HydrogenBond

[HydrogenBond]

If we compare cold blooded critters, to warm blooded critters, the cold blooded animals need solar heating; warmth, to provide activation energy, so its internal chemical reactions can move forward. The analogy is like burning damp wood, which makes a lot of smoke, and then wants go out. To get damp wood to burn, we need to maintain a heat source, with more heat needed the damper the wood.

 

The warm blooded animal is more like the analogy of drier wood, that can burn on its own, and does not need an external heat source to dry the wood. The cold blooded animal's metabolism combustion smolders when it get too cold because the water impacts the combustion. 

Edited March 28, 2015 by HydrogenBond