MCB3208Chs5

MCB3208Chs5 - MCB32F08...

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MCB 32 F08 Chapters 5, Energy Production and Metabolism Graded oxidation of glucose to produce energy (ATP) involves Glycolysis (cytosol) Break down glucose to pyruvic acid, produce reduced cofactor NADH (shuttles electrons) and small amt ATP. glucose (CH 2 O) 6 + NAD + 2ADP +2 P i 2 pyruvic acids (CH 2 O) 3 + NADH + 2ATP [No need to remember this portion inside the brackets First part : glucose + 2 ATP C 6 sugar-(P i ) 2 + 2 ADP ATP has been consumed, energy required. Phosphorylation of glucose traps glucose inside the cell so it cannot escape. Second part: C 6 sugar-(P i ) 2 2xC 3 -P i sugars + 4 ADP + 2 NAD 2xC 3 pyruvic acids + 4ATP + 2NADH + 2H + ] Krebs or citric acid cycle (in mitochondrial matrix) pyruvic acid (C 3 ) combines with coenzyme A to form key intermediate acetylcoenzyme A (C 2 ), which in turn is combined with other molecules in a cyclical series of reactions. This reaction produces little energy but generates both CO 2 (released to the blood stream) and reducing equivalents in the form of NADH and FADH, which will be used later by the mitochondrial membrane. Pyruvic acid (C 3 ) + CoA + NAD AcCoA (C 2 ) + NADH + H + + CO 2 AcCoA (C 2 ) + oxaloacetate (C 4 ) citric acid (C 6 ) C 5 + CO 2 oxaloacetate (C 4 ) + CO 2 FADH is also produced during this cycle, which is then started again. FADH can donate its electrons just like NADH to the electron transport chain, as shown below. ATP also produced. Overall , mitochondria take 3-C sugars (pyruvic acid) produced in the cytosol during glycolysis and metabolize/oxidize them in a series of reactions called the citric acid or Krebs (after the discoverer) cycle, releasing reduced cofactors NADH + H (abbreviated NADH) and FADH 2 (abbreviated FADH) as well as CO 2 and ATP. Oxidative phosphorylation (in mitochondrial membrane) The reduced cofactors (NADH and FADH) are oxidized inside the mitochondria in a last series of reactions that involve molecular oxygen, to produce H 2 O and ATP, called oxidative phosphorylation . NADH + FADH + O 2 ATP + H 2 O + NAD + FAD inner mitochondrial membrane 1
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Many of the important reactions involve oxidation-reduction reactions that are coupled to each other, similar to the coupling that occurs in exergonic and endergonic reactions noted above. Oxidation refers to loss of electrons by a molecule, reduction is gain of electrons. Oxidizing agent : molecule that takes on electrons; reducing agent : molecule that loses electrons. These processes are often accompanied by hydrogens being shuttled between molecules because the hydrogens have one electron and one proton and are small and can be moved around easily. For example, during the breakdown of glucose into smaller 3-C units and during the citric acid cycle,
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MCB3208Chs5 - MCB32F08...

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