Kind of confused me with the stability thing. I guess the way I see it is that energy is absorbed to break a bond and energy is released to form a new bond. In the reaction of methane to methanol you break 1 bond and form 2 bonds. As you further oxidize it you form even more bonds so there should be a net release of energy. Is that a good enough reasoning to use for the mcat? Or should we really go in depth by being familar with those bond energy numbers? I am far from taking the mcat but my classes really didn't go in this depth lol. Also how do you know all this? Is this the level of comprehension we should know for all subjects while studying for mcat?
One last thing, did they mean total energy in general? Or Gibb's free energy? I just finished two semesters of thermodynamics and no where in the course did we use the terms "free energy."
You won't need to memorize bond energy values for the MCAT. They would be provided if a question required them. I learned about this in a summer biochemistry course and was curious about the reasoning, although it wouldn't hurt to understand for the MCAT since these concepts (oxidation/reduction, changes in free energy, bond stability, etc.) deal with topics that would be found on the MCAT. I wouldn't worry about this specific question though. I didn't come across this while studying for the MCAT or anything like that. As for the level of comprehension required for most topics, I would say your best bet is to just work hard to get good grades in all your classes and then use review books for practice questions and going over areas you're weaker in. That will give you the best sense of how in-depth you need to understand concepts. Lastly, I was referring to "Gibb's free energy" when I simply said "free energy." I think those terms are used interchangeably pretty often.
This thread has confused me. So what's the conclusion?
Here's my conclusion:
A compound that gets oxidized loses electrons. When we talk about oxidation of hydrocarbons, which is usually the case in organic chemistry and biochemistry, we are usually talking about a C-H bond changing to a C-O bond. The loss of electrons is essentially due to the fact that when carbon was bonded to hydrogen, carbon was slightly more electronegative than hydrogen and therefore holding on to hydrogens electron a little bit more tightly, but when carbon became bonded to oxygen, the oxygen is much more electronegative, and oxygen pulls much more tightly on the electrons involved in the C-O bond, essentially taking away the electrons from carbon. Recall from general chemistry and physics that electrons exist at certain energy levels in atoms. Electrons possess stored, potential energy that is capable of doing work, so the loss of electrons accompanying oxidation leads to a release of free energy. Another way of understanding why oxidation leads to release of free energy is to consider how the type of bonding changes with oxidation. Stronger bonds are being made with oxidation. For example, initially we might mainly have C-H bonds. Strangely enough, a C-O bond is actually weaker (Look at the bonding energies). This is due to the fact that hydrogen is much smaller than oxygen, so the hydrogen is much closer to carbon in a bond than is oxygen, and consequently, the electrons can be shared more effectively, allowing for a stronger bond. However, oxidation of a hydrocarbon often also forms O-H bonds, as in oxidation of methane to methanol. O-H bonds are very strong polar covalent bonds with higher bonding energies (more energy needed to break them) than C-H bonds. Additionally, oxidation often results in C=O bonds. Double bonds are much stronger than single C-H bonds. In other words, the bonds being formed are harder to break and therefore more stable. Stability is associated with lower free energy, so the stronger bonds resulting from oxidation must be causing a release of free energy. If you also remember from general chemistry, combustion reactions, in which a hydrocarbon is in the presence of oxygen and subjected to oxidation, are highly exothermic, releasing large amounts of energy. These more reduced molecules, such as hydrocarbons, that get oxidized are referred to as fuel molecules. Oxidation of fuel yields free energy, which can be used to add phosphate to ADP to produce ATP. That ATP can then be hydrolyzed to ADP, releasing free energy in the process, which can be used for active transport, etc.
Someone let me know if I'm missing anything or if this explanation has any errors.
