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Sunday, 12 February 2012

Glycolysis & Krebs Cycle




AEROBIC RESPIRATION:
Digestion and muscle action in human and any other animals,sugar transport through the plant body-all such activities
depend absolutely on the high ATP yield of aerobic respiration
      Glycolysis is the first stage of the aerobic pathway two more stages follow.The Pyruvate is completely degraded and
ATP is produced in the second stage-the Krebs cycle and few reactions preceeding it. Also coenzymes NAD+ and FAD pick
up H+ and electrons that are released during the krebs cycle, and in this way NADH and FADH2 form.In the third stage,
Electron transport phosphorylation , the coenzymes give up H+ and electrons to transport systems.Operation of the transport
system commonly leads to the formation of 32 ATP, and this brings the total net yield of the aerobic pathway to 36 ATP.

GLYCOLYSIS:

1) Glucose, a 6 carbon molecule,gets an ATP-derived phosphate group attached to it one end,then gets rearranged into
    Fructose-6-Phosphate.

2) Another ATP -derived phosphate group gets attached at the other end, forming fructose-1,6-biphosphate.

3) This intermediate is split into PGAL and DHAP. Because each of these molecules is easily converted to the other,we can
    say that PGAL have formed.Beyond this point,each occurs twice for each glucose molecule being dismantled.

4) The PAGL gives up 2 hydrogen atoms.Both electrons and one proton(H+) of those atoma are picked up by NAD+ to      
    form NADH. The PGAL also combines with inorganic phosphate.The resulting unstable intemidiate donates a
    phosphate group to ATP.

5) With this formation of two ATP, the original energy investment of two ATP is paid.

6) In the next two conversions, the intermediate gives up one proton and one OH- ion(which combine to form water).
    The resulting intermediate is phosphoenol pyruvate(PEP).

7) The highly unstable PEP readily gives up a phosphate group to ADP,forming ATP.Thus the net energy yield is
    two ATP and two NADH for each glucose molecule oxidized.

8) The end product of glycolysis is pyruvate(the ionized form of pyruvic acid).





AEROBIC RESPIRATION:
Digestion and muscle action in human and any other animals,sugar transport through the plant body-all such activities
depend absolutely on the high ATP yield of aerobic respiration
      Glycolysis is the first stage of the aerobic pathway two more stages follow.The Pyruvate is completely degraded and
ATP is produced in the second stage-the Krebs cycle and few reactions preceeding it. Also coenzymes NAD+ and FAD pick
up H+ and electrons that are released during the krebs cycle, and in this way NADH and FADH2 form.In the third stage,
Electron transport phosphorylation , the coenzymes give up H+ and electrons to transport systems.Operation of the transport
system commonly leads to the formation of 32 ATP, and this brings the total net yield of the aerobic pathway to 36 ATP.

KREBS CYCLE:

1) As the 3 carbon puruvate enters the mitochondrion, enzymes split away its COO- group which departs as CO2.Enzymes
    also transfer a proton(H+) and 2 electrons to NAD+ forming NADH.The 2 carbon molecule remaining is linked to co- 
    -enzyme forming the intermediate acetyl-CoA.

2) The 2 carbon molecule becomes attached to oxaloacetate, the point of entry into the Krebs Cycle, to form the 6 carbon Citrate.

3) Citrate is rearranged into the 6-carbon isocitrate, which is stripped of two hydrogen atoms, with all but one H+ of those atoms being transferred to NAD+ to form NADH. It is also stripped of a COO- group, this being the second CO2 to depart.

4) The resulting intemediate also gives up 2 hydrogen atoms and NADH forms.And it gives up a COO- group which is the
    CO2 to depart.

5) Enough energy is released to phosphorylate ADP to from ATP.

6) In the conversion of succinate to fumarate, 2 hydrogen atoms are transferred to FAD, forming FADH2.

7) In the last conversion, which regenerate oxaloacetate, 2 hydrogen atoms are stripped away and H+ and two electrons
    are transferred to NAD+, forming the last NADH molecule in the cycle.



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