3. Physiology
        3.9. Metabolism and Nutrition
            3.9.1. Metabolism
3.9.1.1. Energy production

Energy production

(Nunn p.276)

Use of glucose to produce energy involves 3 stages:

  1. Glycolysis
  2. Citric cycle (Krebs' cycle)
  3. Oxidative phosphorylation

1. Glycolysis

Under anaerobic conditions

Lactic acid

Lactic acid can be:

  1. converted into liver glycogen
  2. re-converted by to pyruvic acid in the presence of O2, then oxidized in the citiric cycle

Overall effect

For each molecule of glucose

Under aerobic conditions

Same as per anaerobic condition, except:

  1. Conversion of glyceraldehyde-3-phosphate to 3-phosphoglyceric acid (which produces the 2 NADH) occurs in the mitochondria.
    => the 2 NADH are produced within mitochondria
    => may enter oxidative phosphorylation, rather than producing lactic acid.
  2. Pyruvate does not get converted into lactic acid, but diffuses into mitochondria and enters the citric cycle.

2. Citric cycle (Krebs' cycle)

Occurs within the mitochondria.

Produces:

So far, each molecule of glucose produces:

 

3. Oxidative phosphorylation

 

Summary

Anaerobic pathway

Each molecule of glucose

=> 2 pyruvic acid

=> 2 lactic acid + 2 ATP + 2 H2O

(67kJ per mole)

 

Aerobic pathway

Each molecule of glucose

=> 2 pyruvic acid

=> 38 ATP + 6CO2 + 6H2O

(1270kJ per mole)

 

Combustion yields 2820kJ per mole

=> aerobic efficiency = 45%

 

 

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Created20050305
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