First 435 words of the document:
So...the first part of respiration, effectively...glycolysis
So, main things we need to remember when we think about energy transfer in respiration are that, firstly, the
CH bond in glucose is weaker than the OH bond in water. When a bond is broken, energy is taken in when a
bond is made, energy is released. Less energy is needed to break the CH bond, and more energy is released
when the OH bond forms. The second thing to remember is how ATP stores energy:
ADP + Pi ATP this needs an input of energy because the Pi is bound to a water molecule and the
Piwater bond needs to be broken. More energy is put into breaking this bond, than is released when the
ADPPi bond is formed (ATP).
ATP ADP + Pi in this hydrolysis, the Pi released bonds to surrounding water molecules. This formation
of a bond creates a LOT of energy, much more than is taken in through the splitting of the ATP bonds. This is
how ATP stores energy.
Right, so now all the basics are understood, let's start on glycolysis...
So glycolysis occurs in the cell cytoplasm, including sarcoplasm of muscle cells. The glucose used comes
from the cell's glycogen store...
Firstly, the glycogen is converted into glucose
Glucose is really stable, so it doesn't really react with much...this is why we need to add a couple of phosphate
groups to it to make it more reactive. This occurs by the use of ATP. 2ATP go in, 2 inorganic phosphate
groups stay, and 2ADP are released.
Now we've got 2 intermediate 3carbon compounds. To get to pyruvate, both of these 3carbon compounds
are oxidised, and so lose 2 hydrogens EACH. So ultimately we lose 2 x 2H. But they are not LOST! They are
used to reduce a coenzyme: NAD, we'll hear about this later.
So we want to create ATP, that's the whole point of this process. When the intermediate compounds are
oxidised to pyruvate, 4 lots of ADP (4ADP) are phosphorylated to 4ATP. An input of only 2 inorganic phosphate
groups are needed because the other 2 are provided by the intermediate compounds (remember we added
phosphate to glucose earlier?).
So overall we've got a net gain of 2ATP, and glucose has been converted from...glucose to pyruvate, which is a
decrease in energy level (this energy is stored in the ATP produced).
And that's glycolysis :)