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Currently Playing: TCA meets M&Ms - citric acid demo - anaplerotic reactions, etc.

Because biochem's better with some hands-on activities! The TCA Can be used in full or in parts, for both catabolism & anabolism o   Catabolic when used in its entirety - fully oxidizes acetyl-CoA (such as is made from pyruvate) §  Produces the bulk of NADH (and FADH2) from glucose - leads to bulk of ATP that can be produced from glucose catabolism (i.e. most of the energy from glucose does NOT come from glycolysis, but rather it comes from oxphos from electron carriers from the TCA) o   Lots of anabolic functions since it can interconvert 4-6 C intermediates that can be used as building blocks for different molecules §  Acts like a roundabout, but you’ve got to put more in if you take things out (and acetyl-coA does not count!!!!!) ·      Oxaloacetate needs to be present for acetyl-CoA to come in – If you take ANY intermediate out of the pathway you won’t have oxaloacetate, UNLESS you put something more than2 C in   ·      Anaplerotic reactions are reactions that regenerate pathway intermediates o   For something to be anaplerotic to the TCA, it must put in more C than get taken out (more than 2C) §  You lose 2C (as 2 CO2) per turn of TCA cycle, so for humans, must add something more than 2C to keep it going ·      The glyoxylate shunt allows plants, bacteria, fungi, & protists to bypass the need for more than 2C compounds. It lets them sustainably synthesize oxaloacetate (and thus glucose) with just acetyl-CoA (e.g. from fats). We mere humans don't have this metabolic superpower... o   Since oxaloacetate (technically malate…) from the TCA can be used to make glucose, things that are anaplerotic for the TCA can be called glucogenic ·      You need to go around the decarboxylation part of the cycle 1 time per 2C o   E.g. if you put oxaloacetate (4C), you’ve gotta go around the full circle twice; citrate (6C), 3 times, α-ketoglutarate ~2.5 (since you’re coming in midway, past the decarboxylations) Note: I realized I misspoke – you lose 1C the next cycle regardless, it's the 3rd cycle you might or might not, sorry! More serious TCA talk: more on all sorts of metabolic stuff: https://bit.ly/bbmetabolism & https://www.youtube.com/playlist?list=PLUWsCDtjESrHXBgulruKEOrNXQ21_0gyc    more about all sorts of things: #365DaysOfScience All (with topics listed) 👉 http://bit.ly/2OllAB0 or search blog: http://thebumblingbiochemist.com                                 #scicomm #biochemistry #molecularbiology #biology #sciencelife #science #realtimechem