Anaerobic pathways
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Anaerobic Pathways. Organisms use these pathways in oxygen-poor environments such as Wet environments Human digestive tract Deep underground. Organisms in these environments can obtain energy from glycolysis in a limited way Step 6 (G3P to BPG) reduces NAD + to NADH.

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Anaerobic Pathways

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Anaerobic pathways

Anaerobic Pathways


Anaerobic pathways

  • Organisms use these pathways in oxygen-poor environments such as

    • Wet environments

    • Human digestive tract

    • Deep underground


Anaerobic pathways

  • Organisms in these environments can obtain energy from glycolysis in a limited way

  • Step 6 (G3P to BPG) reduces NAD+ to NADH.

  • If no oxidation of NADH occurs due to lack of oxygen, NAD+ will be limited thus stopping glycolysis.

  • Some organisms have a different route of oxidizing NADH called fermentation.

  • Bacteria have many different routes

  • Eukaryotes have 2 methods


Fermentation in eukaryotes

Fermentation in Eukaryotes

  • The two methods of fermentation in Eukaryotes are:

    • Ethanol fermentation

    • Lactic Acid Fermentation (Lactate fermentation)


Ethanol fermentation alcohol fermentation

Ethanol Fermentation = alcohol fermentation.

  • Glucose undergoes glycolysis to produce 2 pyruvates, 2NADH + 2H+ and 2 ATP net.

  • The 2 pyruvates are decarboxylated and form 2 acetalaldedydes.

  • The two acetalaldedydes are reduced by 2NADH from glycolysis forming 2 ethanols and 2 NAD+

  • CO2 and ethanol are waste products

  • Example of an organism that carry out ethanol fermentation is yeast.


Alcohol fermentation

Alcohol Fermentation

One of main function is to resupplies glycolysis with NAD+


Uses of alcohol fermentation

Uses of alcohol Fermentation

  • Humans use alcohol fermentation to make breads, pastries, beers, wines, liquor and soy sauce.

  • These are products of fermentation.

  • Accumulation of ethanol in an organism can cause death.


Anaerobic pathways

Lactate Fermentation

  • During exercise, muscles respire faster than the body can supply oxygen.

  • Oxidative respiration slows down and lactic acid fermentation begins

  • Glucose undergoes glycolysis to produce 2 pyruvates, 2NADH + 2H+ and 2 ATP net.

  • The 2 pyruvates are reduced by 2NADH from glycolysis forming 2 lactates and 2 NAD+

  • NAD+ generated goes back to glycolysis

  • Lactate accumulates


Lactate fermentation

Lactate Fermentation


Anaerobic pathways

  • Accumulation of lactate causes stiffness, soreness and fatigue

  • This reaction is reversible

    • When exercises cease, andoxygen is present:

    • Lactate is shuttled to liverto be oxidized.

    • Pyruvate and NADH are replenished

  • Pyruvate gets into the mitochondria where it undergoes aerobic cellular respiration.


Anaerobic pathways

Homework

  • Pg. 194: # 1-4, 6, 7


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