Cheers man, but does NADPH also carry electrons as well as hydrogen atoms?
I thought that it was electrons that actually supplied the energy. If the bonds in ATP are broken, then where does this energy from the 'bond' come from? Is it like heat energy or?
Yeah NADPH carries 2 electrons and one hydrogen atom (this is referring to exchangeable electrons and hydrogens). Electron carriers such as NADPH, NADH and FADH2 do carry high energy electrons (think of these molecules as strong reductants, strong reductants can provide higher voltages in a galvanic cell because they hold electrons with higher potential energy) but this energy can't be accessed in a lot of biochemical reaction pathways for example the synthesis of glycogen requires phosphorylation using ATP, it pairs an endergonic reaction (polymerisation) with a highly exergonic reaction (ATP --> ADP), overall this makes the reaction favourable and allows it to occur. This reaction can't be achieved using an electron carrier because well chemistry.
The high energy bonds in ATP are a form of chemical potential energy which is used to create different forms of chemical potential energy (e.g. synthesis of carbohydrates/proteins/DNA/lipids) as well as maintaining intracellular and extracellular environments (e.g. Na+/K+ ATPase antiporter (maintains electrochemical potential energy)). Of course energy conversions are almost never 100% and a lot of energy is released as heat during these processes.
So where does this energy come from? Well in the beginning there was a big bang... etc etc light energy from the sun etc photosynthesis etc im not a plant guy etc etc glucose. ATP can be formed in two ways, through enzymatic cleavage of a high energy phosphate bond or through oxidative phosphorylation by ATP synthase. The catabolism of glucose begins with glycolysis, this pathway produces ATP enzymatically through a series of reactions involving the breakage of carbon-carbon bonds which creates reactive functional groups (specifically aldehyde groups) which presents a great source of chemical potential energy. This is used to enzymatically add inorganic phosphate which is followed by removal of the phosphate group using ADP to produce ATP. During this pathway the glycolytic intermediates also get oxidised, causing the reduction of NAD+ to NADH. At the end of glycolysis you get pyruvate which is oxidatively decarboxylated (oxidation reaction that releases a CO2 molecule) to acetyl CoA which then enters Krebs cycle. The catabolism of different biomolecules provide energy in their own pathway but they all converge at acetyl-CoA which can enter Kreb's cycle.
Kreb cycle intermediates are oxidatively decorboxylated to produce electron carriers NADH and FADH2 and CO2. These electron carriers can then donate their electrons (oxidation) to the electron transport chain which involves a series of redox reactions terminating at the reduction of oxygen, and just like in galvanic cells, the energy released during these redox reactions is harnessed a sort of electrical current which induces changes in the confromation of inner mitochondrial membrane (IMM) proteins and the pumping of hydrogen ion across the IMM. This sets up an electrochemical gradient. Hydrogen ions want to move back into the mitochondrial matrix because it will be traveling down its electrical and concentration gradients: from a region of high concentration and high positive charge to a region of low concentration and low positive charge. This electrochemical potential energy is harnessed by ATP synthase to create chemical potential energy in the bonds of ATP.
So overall, the aerobic respiration of glucose involves the breakage of carbon-carbon bonds and the oxidation of carbon molecules which is utilised by the body for energy. Aerobic respiration is like the combustion of glucose but carried out over a convoluted series of controlled steps allowing the controlled the release of energy.
Thats probably more detail than you need or asked for but I hope it helps you understand whats going on better.
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