Without enzyme, how hot would body need to be?

[mishima]

What temperature would the human body need to be in order to sustain all necessary metabolism reactions in the absence of a catalyst? I know this is unreal, I am just curious of an order of magnitude estimate.

 

[SteamKing]

You are assuming that the same or similar metabolic reactions would take place without enzymes. This may not be a valid assumption, no matter how much hotter the body got.

 

[mishima]

Are you saying that for some biochemical processes, simply having 2 reactants (substrates) collide with sufficient activation energy is NOT enough to start a reaction? Could this be because an enzyme combines the 2 in a way (an orientation) that is very unlikely to occur in a random collision, or is there something else?

 

[SteamKing]

Are you saying that for some biochemical processes, simply having 2 reactants (substrates) collide with sufficient activation energy is NOT enough to start a reaction? Could this be because an enzyme combines the 2 in a way (an orientation) that is very unlikely to occur in a random collision, or is there something else?

All I'm saying is that catalysis doesn't always work by reducing the activation energy for a given reaction. Other factors, like acidity or alkalinity, which do not depend on temperature, may be significant in whether a certain catalyst will be effective at increasing reaction rates.

http://en.wikipedia.org/wiki/Catalysis

 

[Ygggdrasil]

There are also cases where enzymes are important for their specificity in addition for their ability to perform catalysis. For example, many signalling processes within the cell are regulated by the transfer of a phosphate from ATP to a specific residue on a protein. If this process were occurring thermally, transfer of the phosphate from ATP to water would be the dominant reaction, so protein phosphorylation would almost never occur.

Furthermore, some essential metabolic reactions in the cell require enzymes. A good example is the synthesis of ATP from ADP and phosphate by ATP synthase. This reaction requires an enzyme in order to couple the energy from an electrochemical gradient to the thermodynamically unfavorable synthesis of ATP.

 

[epenguin]

Agree with Ygggdrasil but would put it still more strongly: without the specificity properties of enzymes life is surely impossible and unimaginable. You could have reactions with unspecific catalysts but they would just be a mess, everything would degrade - in particular the example he gives phosphates would just transfer to water instead of being channeled (albeit everything obey thermodynamics and free energy decrease) to phosphorylation of other things, an example of the coupling of reactions that is really everything in biochemistry.

 

[mishima]

Hmm, alright thanks guess I need to read more on this specificity property, thanks for the eye opener.