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    Hey guys,

    Basically, energy production in the human body is hugely a weak point of mine. I just struggle to grasp it! I have a nutrition exam coming up for my module at university, and basically, it's likely that one of the essay questions I have to write will be based on Energy Production Systems in the human body.

    The essay will be expected to cover

    The PCr (Phosphocreatine) System
    Glycolysis
    TCA (Krebs) Cycle
    Electron Transport Chain
    Electron Carriers

    I do believe these are the main energy production systems and all link maybe in some way. During this module, this has been my biggest struggle, my lecturer has just thrown us straight in the deep end of this, and I know I should know this by now, but I just don't.

    So my question is, anybody able to explain any of those simply?

    Or got any good online resources that explain it?

    Thanks guys, will rep those who help
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    All of the above (bar the PCr system) form energy in the form of ATP (Adenosine Triphosphate), which gives out energy be losing a phosphate group. Glycolysis is where Glucose (6C) enters the cell via facilitated diffusion and is broken down in the cytosol in to two molecules of pyruvate (3C). The first step of this reaction is to phosphorylate glucose using two molecules of ATP. This breakdown gives out enough energy to form four molecules of ATP by substrate-level phosphorylation two of which will return to the beginning again. The last product of this breakdown is a proton to H+, which is a de-hydrogenation reaction. This used to reduce NAD to NADH, which enters the mitochondria. Therefore glycolysis is as follows:

    Glucose + 2 ATP -> 2 Pyruvate + 2 H+ + 4 ATP

    The Pyruvate then enters the mitochondria and undergoes the Link reaction, which uses a Decarboxylase Enzyme to remove CO2 from the pyruvate. A H+ is also lost and is used to reduce NAD to NADH. The product of this reaction is then combined with a enzyme called Co-Enzyme A to form Acetyl Co-Enzyme A (2C).

    The Krebs cycle occurs in the Matrix of the mitochondria where Acetyl Co-Enzyme A is combined with Oxaloacetate (4C) to from citrate (6C). One rotation of the Krebs cycle forms 2 CO2, 6 NADH, 2 FADH (Like NAD) and one ATP by substrate level phosphorylation. The Ocalocetate is then re-used.

    Oxidative Phosphorylation occurs at the Crista in the mitochondria. This is where all of the NADH and FADH molecules end up. Here they release and H+ and an electron(I've never been able to work out where they come from). The electrons are fed in to the cytochromes, where they are used to pump H+ ions through the Crista in to the intermediate space. The H+ ions then move down their electro-chemical gradient through a stalked particle. This is where the phosphorylation occurs udner the control of ATP synthase and the energy produced by the moving H+ ions is used to attach a phosphate group to a ADP (Adenosin Diphosphate) molecule. The electrons from the electron transfer chain or cytochromes are combined with the used H+ ions and oxygen to form water. The whole process can be referred to as Chemiosmosis.

    I hope that this description simplifies it somewhat. Sorry if reading this hasn't helped you.
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    Thank you, it's helped a great deal! This has given me the basic outline of what I need, thanks to your simplified version I can slowly go in depth for it, I've got 2 weeks to learn it for one of my two essays, so I appreciate your swift response. The question will most likely ask us to talk about the importance of ATP and describe the energy systems used.

    So Oxidative Phoshorylation is the ETC I'm guessing? Sorry if I've got that wrong!

    But it helps me a great deal! How easy/hard is it to memorise each stage of the Glycolysis cylce and TCA cycle? I'm considering drawing them in my exam to show I understand it deeply, and an accurate drawing will gain me marks because I'll be able to link my work to this diagram if I can draw it.

    Am I right in thinking Glycolysis has 10 steps, where TCA has 8?
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    The ETC is part of the process that enables Oxidative Phosphorylation.

    As for the cycles, TCA is 8 steps and I find the diagram on page one of http://web.ku.edu/~crystal/taksnotes...tes/chp_16.pdf quite clear. For glycolysis the reaction is a ten step one but I find this site http://www.elmhurst.edu/~chm/vchembo...colysisrx.html quite good even though it shows it as a nine step reaction.

    Memorizing either isn't the easiest of tasks though.
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    (Original post by Tristian Fox)
    The ETC is part of the process that enables Oxidative Phosphorylation.

    As for the cycles, TCA is 8 steps and I find the diagram on page one of http://web.ku.edu/~crystal/taksnotes...tes/chp_16.pdf quite clear. For glycolysis the reaction is a ten step one but I find this site http://www.elmhurst.edu/~chm/vchembo...colysisrx.html quite good even though it shows it as a nine step reaction.

    Memorizing either isn't the easiest of tasks though.
    Thank you! So do you know total yield from both processes?

    I have it down as:

    4 ATP
    2 FADH
    8 NADH

    This bit is pretty important for me!
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    That's right for the net yield of the two processes for one molecule of glucose.

    2 ATP form glycolysis and 2 ATP from TCA

    2 FADH from TCA

    2 NADH from glycolysis and 6 NADH from TCA (Plus 2 NADH from the Link Reaction if you want to include it)
 
 
 
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