Help , why does bio contradict chemistry or vice versa ?
I'm taking A level chemistry and A level Bio , and in Bio , for some reason , breaking bonds releases energy whereas forming bonds needs/takes in energy
But in chemistry , bond breaking is endothermic and bond forming is exothermic
It doesn't make sense to me
Comments
It takes energy to break a bond, sure, or the bond would not exist in the first place. However, when a bond is broken, some other condition has to take its place, and that other condition requires some energy to come into existence. There are also two aspects to every chemical change: work, and heat. Some things use energy mostly for work (shoving atoms into a specific position, say, or pulling an atom out) and some absorb or release heat (change temperature by giving or taking kinetic energy to/from atoms and molecules).
Exothermic and endothermic only refer to the temperature part. Many reactions are endothermic, take heat while doing work so there is still a reduction in total energy of the system. It is more common that reactions also release some heat while doing some work that gets to a more stable condition, but it is not the only way. Sometimes even, a reaction can give off heat yet have to do work (get into a more difficult orientation than existed at the start).
There is no contradiction between bio and chemistry. You have not properly understood the explanation, or someone has made a false claim.
In biology, there is no doubt that many reactions that occur are allowed because that is how they power the function of the life form itself. But something had to make those reactants into the way they are first. Do not confuse heat (-thermic) with total energy involved.
Making and breaking bonds....
Yes, I've wondered, too, how the biology people get it wrong, but they persist in saying that "bonds store energy" and that "energy is released as bonds break." This is a misconception that gets handed down from one biologist to another.
In fact, it requires energy to break a bond (endothermic) and energy is released when a bond forms (exothermic). New bonds form because the compounds in which they are found are at a lower total energy than the reactants. Therefore, as these new compounds are formed the "extra" energy is given off.
The breaking and making of bonds occurs together as the reaction proceeds and what appears to the biologists way of thinking is that energy is being released as the bonds in the reactants are breaking, when it fact, the energy is being released as new bonds form. But since all of this is occurring over the same time interval, they don't seem to understand the difference.
E
|.....................* <--------- activated complex
|................* .......*
| *....*.... * <---------------- reactants
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|..................................* ....* ......* <--- products
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...... Reaction Pathway