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Why does the human body need such a high temperature?

  1. Jan 9, 2015 #1
    If our body temperature falls below 30 degrees C or so, it stops functioning properly and we die.
    30 C seems still a rather warm temperature for normal chemical reactions to be able to occur, and in most environmental conditions inhabited by men it still represents a temperature gradient compared to the cooler external environment.
    Which metabolic processes or chemical reactions fail at such temperatures? Why do we need such a high body temperature to function properly?

    And a related question: By now life has evolved a wide spectrum of solutions to cope with a relatively wide range of external temperatures, from Tardigrades or frogs who can survive in freezing temperatures (or warm blooded animals of course) to thermophile bacteria who can survive over-boiling temperatures, but for simpler very early life to develop, which is the range of temperatures believed to be needed?
     
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  3. Jan 9, 2015 #2

    Doug Huffman

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    Biological whys are a step onto the slippery slope of teleology. I suspect lower temperatures cause too slow reactions to survive. Here the temperature is about zero at the moment, and a usually deadly reptile would just be easy picking food.
     
  4. Jan 9, 2015 #3

    Pythagorean

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    In neurons, current in and out of the cell is mediated by ion channels. The time "constant" of channel kinetics is extremely sensitive to temperature and changes in the time constant can lead to a different time course for currents which can lead to a different effective threshold for neuron firing.

    I don't know how much of an effect this would be, or how it would emerge in the whole organism. There may be metabolic or physical consequences that come first or are more deleterious.
     
  5. Jan 9, 2015 #4

    Andy Resnick

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    You are basically asking why humans don't hibernate: Hibernating mammals have core body temperatures near (or even below) 0°C

    http://www.ncbi.nlm.nih.gov/pubmed/14506303
     
  6. Jan 9, 2015 #5
    No, I was not really asking that, although it might be related. Do you mean that physical body functioning does not need such a high temperature, and that our requirement for high body temperature happens only because we need significant brain activity to keep our body functioning? So that it is actually only the brain, and not the rest of the body, which needs such a high temperature to keep on working? If that's the case this might be in line with the previous reply by Pythagorean.

    In other words, do you suggest that when our body temperature drops below 30 C it is our brain which ceases to work properly (causing the failure of metabolic processes controlled by the brain) and not a failure of the metabolic processes themselves due to insufficient temperature?
     
    Last edited: Jan 9, 2015
  7. Jan 9, 2015 #6

    Doug Huffman

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    Nerve function is similar through out the human body.
     
  8. Jan 9, 2015 #7

    Ygggdrasil

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    All enzymes (as well as other functional molecules like channels) in the body have evolved to work optimally at 37oC, and changing the temperature can alter their rates as well as their stability. Because the rates of many enzymes must match with the rates of other processes and changing the temperature can have unequal effects on different enzymes, changing the temperature of the body will have disastrous effects on many processes in the body (at low temperatures, reactions won't happen fast enough, and at high temperatures, enzymes will start unfolding).

    This is not to say that all enzymes have to work at 37oC. Different organisms have evolved different optimal temperatures for their enzymes. For example, arctic shrimp have enzymes evolved for cold temperatures while thermophilic bacteria have enzymes optimized for high temperatures. Thus, another question may be why did humans (and other similar mammals) evolve to have a core body temperature above the ambient temperature?

    The answer to this may simply be that it is easier for the body to warm itself in cold environments that it would be to shed excess heat in warm environments. Metabolic processes generate a lot of heat which will keep the body warm, and the body can expend energy for the specific task of generating heat. Removing heat, however, relies solely on heat exchange with the environment which is probably fairly inefficient means to cool a body with a relatively low surface area to volume ratio.
     
  9. Jan 9, 2015 #8
    Thanks to all, but I'm still missing a reasonable enough answer. Which human metabolic reactions precisely fail to occur at temperatures around 30 C causing death? If that's what happens of course, some posts suggest that temperature is not the issue for the metabolic processes and reactions sustaining our life, but only for the functioning of the neurological system supporting fundamental metabolic processes.
     
  10. Jan 9, 2015 #9

    Evo

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    You are asking about hypothermia. Hypothermia is dangerously low body temperature, below 95 °F (35 °C).

    http://en.wikipedia.org/wiki/Hypothermia#Signs_and_symptoms

    http://en.wikipedia.org/wiki/Hypothermia#Pathophysiology
     
    Last edited by a moderator: May 7, 2017
  11. Jan 9, 2015 #10

    Pythagorean

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    As far as the nosology is concerned, hypothermia is more of a symptom-based disease classification, whereas the OP is asking about the pathology (mechanism) of hypothermic death.
     
  12. Jan 9, 2015 #11

    Evo

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    That's covered in the wiki article. If he wants more in depth details of what happens with the shutdown of organs as body temperature decreases, he can look up the symptoms listed in the wiki.
     
  13. Jan 9, 2015 #12

    Pythagorean

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    Yggg's post is probably the most informed. It suggests that there's no single enzyme failure; that in cold temperature many operate at suboptimal speeds which causes systemic failures (i.e. higher level processes begin failing as at least one of their dependent enzymes). Since there are so many enzymes underlying biofunction and they are spatially distributed throughout the body, I'm not sure it would be accurate to pinpoint one enzyme, as the specific details of the body's temperature loss (such as does the brain reach 28 first or the heart?) will affect which enzyme (or set of enzymes) is affected first.
     
  14. Jan 9, 2015 #13

    Ygggdrasil

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    The question is somewhat akin to asking, what components of a radio fail if you dunk it in a bathtub full of water. Hypothermia will induce multi-system organ failures, so as Pythagorean says, it's probably difficult to determine which organs failures (or combinations of failures) are most responsible for death. Skimming through the wikipedia article suggests to me respiratory or heart failure, which could be due to dysfunction of channels that signal breathing and heart beat.

    There has been research on using hypothermia as a medical tool to limit damage to tissues during heart attacks or stroke, so you may be able to find more information by digging through the medical literature. For example, here's an article that pops up from a quick google search.

    That's a good question that for which we don't have a good answer. Jack Szostak has an http://www.nature.com/scientificamerican/journal/v301/n3/full/scientificamerican0909-54.html speculating that the best environment would have been a volcanic pool with a temperature gradient that could drive convection that could shuttle the protocells between warm and cold temperatures for different reactions to take place. He also notes that many essential nutrients like phosphate are poorly soluble at cold temperatures, necessitating warmer environments. This is, of course, pure speculation, but it would make sense for such environments to exist and to be plausible spots for the origin of life. Other researcher, however, have a number of other ideas (for example, I remember one seminar where the speaker speculated that life originated in shallow pools that would periodically dry up, concentrating the reagents to allow chemistry to occur, then be rehydrated later).
     
    Last edited by a moderator: May 7, 2017
  15. Jan 9, 2015 #14

    Andy Resnick

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    No, at least I don't think that's what I meant. What I meant was that considering torpor/hibernation means re-evaluating what you define as 'body functioning'. Hibernation is not simply sleep-

    "Hibernators’ lungs become covered with a thick deposit of mucus and collagen like those seen in people with asthma, and their brains show changes that resemble those of early-stage Alzheimer’s. Some species lose memory during hibernation. Most surprising of all, some show symptoms of sleep deprivation when they finally wake."

    "As their body temperature drops, hibernators also remove the lymphocytes (white blood cells) from their blood and store them in the lymph nodes. And within 90 minutes of awakening, these reappear. This damping down of the immune system prevents a general inflammation in the body during rewarming – the very thing that would cause humans and other non-hibernators to suffer kidney damage."

    http://www.bbc.com/future/story/20140505-secrets-behind-the-big-sleep

    In humans, hypothermia can (intentionally or not) be helpful as a survival strategy- surgery, being submerged in a cold lake, etc. As you can see, there are many unanswered questions.
     
  16. Jan 11, 2015 #15
    its bcuz most enzymes in our body work best at 37 degree celsius . enzyme is a catalyst for metabolic reaction, if we cannot provide the optimum temperature for enzyme,it will slow down the metabolic reaction rate
     
  17. Jan 12, 2015 #16
    lower temperature --> less kinetic energy of enzyme and substrate -->the chance of formation of enzyme-substrate complex decrease -->lower reaction rate(e.g respiration ,reaction that break down harmful substances(H2O2),etc) --> deaths of organisms

    hope this can help
     
  18. Jan 12, 2015 #17
    Yes all the replies helped, TX
     
  19. Jan 14, 2015 #18
    May I know if all kinetic energy of enzyme and substrate come from respiration (ATP) or do they occur as a result of heat from the surrounding environment? I'm thinking that at 30 Celsius.. all atoms and molecules vibrate because they are not at absolute zero.. so do enzyme Brownian motion occurs because they are not at absolute zero temperature or all due to ATP process?
     
  20. Jan 14, 2015 #19
    the temperature of surrounding is usually lower that our body,which means heat will lose from the body to the surrounding.
     
  21. Jan 14, 2015 #20

    Ygggdrasil

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    All enzymes use thermal energy (i.e. energy derived from collisions with molecules in their environment) to provide the activation energy required for the chemical reaction to occur. If the chemical reaction is thermodynamically favorable (i.e. the products have a lower free energy than the reactants), thermal energy is sufficient for the enzyme to perform its function. If the chemical reaction is not thermodynamically favorable, the enzyme's action must be powered by another thermodynamically favorable process, such as the hydrolysis of ATP.
     
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