I Why do we need to supply energy to a biological body to keep entropy decreasing?

  • Thread starter fxdung
  • Start date
180
5
Why when we supply energy for biological body then the body can keep entropy not increase?Because we know that by definition temperature equals partial derivative of internal energy to entropy.So that when temperature being constant,if internal energy increase(supplying energy for body) then leading to increase entropy, but not decreasing entropy.
 
Last edited:
19,280
3,818
Why when we supply energy for biological body then the body can keep entropy not increase?Because we know that by definition temperature equals partial derivative of internal energy to entropy.So that when temperature being constant,if internal energy increase(supplying energy for body) then leading to increase entropy, but not decreasing entropy.
The partial derivative of internal energy with respect to entropy at constant volume and number of moles of all chemical species.
 
180
5
Why a mature body(constant volume and number of moles of all chemical species) still needs to supply energy?Why at this condition entropy does not increase while we supply energy?Please explain to me :Why in general cases(in biology) if we want to decrease entropy we must supply energy?
 
Last edited:
1,897
200
Supplying energy by itself only increases the entropy.
The net effect of supplying chemical energy to the body and the body losing energy as heat energy at a low temperature to the environment is a reduction of entropy.
 

Vanadium 50

Staff Emeritus
Science Advisor
Education Advisor
23,099
5,388
I think unfortunately the English here is not understandable. In particular, the title suggests that without adding energy, entropy would decrease. Is that what is meant?
 
180
5
The title has been edited by admin. But the origin meant without adding energy, entropy would increase.
 

berkeman

Mentor
55,541
5,652
The title has been edited by admin. But the origin meant without adding energy, entropy would increase.
Apologies. I was guessing when I tried to fix up the title. Here is the original title:
'Why we need supply energy to keep entropy decrease?'
What would you like it changed to?
 
180
5
I think we omit the word ''from''.
 
17
4
Does the entropy of a living organism ever decrease except for trivial reasons like losing weight or cooling off? My impression is that eating food does not decrease your entropy. It prevents you from reaching maximum entropy, provided that you are also excreting to balance the food intake. Can someone confirm or refute this impression?
 
180
5
Do cold blood animals and plants emit heat to decrease entropy?If not, how can they decrease entropy when we supply energy for them?I do not know whether it prevent from reaching maximum energy or it decrease entropy.What is the mechanism of the process of old and death?
 

Andy Resnick

Science Advisor
Education Advisor
Insights Author
7,262
1,624
Why a mature body(constant volume and number of moles of all chemical species) still needs to supply energy?Why at this condition entropy does not increase while we supply energy?Please explain to me :Why in general cases(in biology) if we want to decrease entropy we must supply energy?
Your assumption is wrong: you do not exist with a constant number of moles of all chemical species.
 
7
5
Why when we supply energy for biological body then the body can keep entropy not increase?
We need to supply energy (from a battery) to a refrigerator in a room to have a decrease of entropy (inside refrigerator cool, outside warm). the refrigerator is a open system, and it's temperature reach a constant value, so it's entropy. Entropy of the refrigerator+room (closed sustem) increase, related to the efficiency of the compressor+motor, and dissipation in the battery.

A biological body is a (complex) open system (respect to outside world) . the input energy make a work (made by biochemical processes) to decrease/or mantain constant entropy, and get a constant temperature dissipating heat resulting from the processes.
 

Lord Jestocost

Gold Member
2018 Award
420
281
Biological organisms are open systems which exchange permanently matter and energy with the environment to maintain a so-called nonequilibrium steady state. They are self-organizing dissipative structures: “…the maintenance of order in actual living systems requires a great number of metabolic and synthetic reactions as well as the existence of complex mechanisms controlling the rate and the timing of the various processes “(Ilya Prigogine, Gregoire Nicolis and Agnes Babloyantz, Physics Today). The high degree of organization of biological organisms (low-entropy structures) is perpetuated by a constant input of energy, and is offset by an increase in the entropy of the environment.

Recommendation: “The Theory of Open Systems in Physics and Biology” by Ludwig von Bertalanffy (Science 1950: Vol. 111, Issue 2872, pp. 23-29)
 
17
4
Do cold blood animals and plants emit heat to decrease entropy?If not, how can they decrease entropy when we supply energy for them?I do not know whether it prevent from reaching maximum energy or it decrease entropy.What is the mechanism of the process of old and death?
I'm not a biologist, or even a scientist, but I would say yes, any living thing that metabolizes food gives off heat. Even "cold-blooded" animals. They just don't maintain their body temperature within as narrow a range as "warm-blooded" animals. As for why living things typically age and die, I don't know the answer. I don't think that has a thermodynamic explanation, at least not in terms of entropy. My guess is that it is more hardware-specific, and not a general principle. As far as ordinary thermodynamics is concerned, a living thing could maintain its mature steady state forever, repeating the cycle of eat->respire->metabolize->excrete forever. Averaging over the cycle, the energy and entropy of the living thing does not change. It acts as a kind of channel, dissipating the high quality energy in food to the lower quality energy of heat and waste products. In doing this, it is analogous to a heat engine that repeats a cycle forever, transferring thermal energy from a high temperature (high quality) to a low temperature (lower quality), and doing some work in the process. In the case of a living thing, the work output redirected back to itself in the form of maintenance and repair. So a living thing is sort of like a self-building and self-repairing engine.
 
180
5
Why in some books say that the process of age and die is caused by increasing entropy(by second law of thermodynamics)?
 
17
4
Why in some books say that the process of age and die is caused by increasing entropy(by second law of thermodynamics)?
I've read something similar in a book written by an ecologist (I think it was). It is mumbo jumbo. Any macroscopic change at all is accompanied by a net increase in entropy, in accordance with the second law of thermodynamics. So there's no particular reason why ageing and dying are necessary to comply with the second law. If there were, one would have a hard time explaining why growth and development ever happened in the first place.

The book I have in mind is called The Myth of Progress. In general, it is an excellent book that I would read again. But the author says that developing systems (living organisms, ecosystems, societies, etc.) acquire an "entropy debt" that has to be paid off by inevitable senescence and disintegration. Presumably, by becoming more organized and "ordered" the systems have done something contrary to the law of entropy, and have to compensate for it later. This is complete nonsense. You can't be in debt to the second law of thermodynamics. It doesn't work like finance, where you can make purchases on credit. It's hard to see how a scientist with a PhD could have that kind of basic misunderstanding.

That being said, there may be some other principle of energetics (not the 2nd law of thermo) that makes ageing and dying the norm for living systems. For example, I have read in other ecology books, particularly by Eugene and Howard Odum, that the turnover rate is an important factor in the development of ecological systems. By turnover rate, I mean how fast matter goes through cycles (like the water cycle, carbon cycle, nitrogen cycle, etc.). It could very well be the case that having individual organisms be "disposable" allows matter to cycle faster, and thus energy to flow through the system more quickly.

But there are a few weird living things that apparently do not age or die of natural causes. They have to get eaten or suffer some other accident to die. So ageing and dying is not general enough to be a consequence of the second law of thermodynamics.
 
"In statistical mechanics, a microstate is a specific microscopic configuration of a thermodynamic system that the system may occupy with a certain probability in the course of its thermal fluctuations. In contrast, the macrostate of a system refers to its macroscopic properties, such as its temperature, pressure, volume and density." (From Wikipedia)

So if you consider an organism as a system in a macrostate 'Alive', a large number of microstates then correspond to this macrostate. Meaning there a lot of ways for the organism to be alive.
For example, if you would switch the position of two molecules, the organism would be in a different microstate but it is still alive. But would you switch its hart with its brain, the microstate would correspond to the macrostate 'Dead'.

"Entropy is an extensive property of a thermodynamic system. It is closely related to the number of microstates that are consistent with the macroscopic quantities that characterize the system." (From Wikipedia)

So the most probable macrostate the organism will be in is the macrostate with the most microstates corresponding to it. The system will eventually end up in that macrostate what is also known as the equilibrium state. Therefore the equilibrium state is the state with maximum Entropy.
There are a lot more possible ways for the organism to be in a microstate corresponding to the macrostate 'Dead' than to the macrostate 'Alive'.
So 'Dead' is the equilibrium state of the organism it will eventually be in.
 

hilbert2

Science Advisor
Insights Author
Gold Member
1,246
379
I've read something similar in a book written by an ecologist (I think it was). It is mumbo jumbo. Any macroscopic change at all is accompanied by a net increase in entropy, in accordance with the second law of thermodynamics. So there's no particular reason why ageing and dying are necessary to comply with the second law. If there were, one would have a hard time explaining why growth and development ever happened in the first place.
Yes, for example, cancer cells don't age and die if they are kept in a solution of nutrients. Or at least they live until they acquire enough random DNA damage to make them unable to sustain their basic energy metabolism.

However, the 2nd law of thermodynamics requires that anything living will die at latest when the whole universe reaches maximum entropy (heat death). I don't think you can avoid that, especially if we live in a finite universe.
 
17
4
So the most probable macrostate the organism will be in is the macrostate with the most microstates corresponding to it. The system will eventually end up in that macrostate what is also known as the equilibrium state. Therefore the equilibrium state is the state with maximum Entropy.
There are a lot more possible ways for the organism to be in a microstate corresponding to the macrostate 'Dead' than to the macrostate 'Alive'.
So 'Dead' is the equilibrium state of the organism it will eventually be in.
Yeah, this is true if you seal the organism off in a box so that it is isolated from its surroundings. Or if you just wait until the heat death of the universe. But neither of these situations is of direct relevance to why living things get old and die. It can't be a consequence of the 2nd Law of Thermo. Else why were they alive and growing and developing in the first place?

Edit: I just realized you might have been answering the OP's original question. The last few posts have been about why organisms age, so I was interpreting your answer as a response to that, which it may not be.
 
180
5
I read somewhere saying that entropy of a system increasing because of random disturbance from universe.But for whole universe what cause it increase entropy?
 
180
5
Yes, I did a misunderstand.The author saying with determination dynamics.But do not saying about quantum states.
 

Want to reply to this thread?

"Why do we need to supply energy to a biological body to keep entropy decreasing?" You must log in or register to reply here.

Related Threads for: Why do we need to supply energy to a biological body to keep entropy decreasing?

Replies
21
Views
2K
  • Posted
Replies
4
Views
31K
  • Posted
Replies
8
Views
12K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top