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Anaerobic Respiration

Anaerobic Respiration. Lactic Acid Fermentation Oxygen is not present Conversion of 2 molecules of pyruvate into lactic acid when oxygen is not present Happens during vigorous muscle exercise Liver converts lactic acid back into glucose . Lactic Acid Fermentation.

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Anaerobic Respiration

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  1. Anaerobic Respiration • Lactic Acid Fermentation • Oxygen is not present • Conversion of 2 molecules of pyruvate into lactic acid when oxygen is not present • Happens during vigorous muscle exercise • Liver converts lactic acid back into glucose

  2. Lactic Acid Fermentation • Occurs in humans when • Demand for ATP exceeds the rate at which O₂ can be supplied • Process • Pyruvate is converted into lactate • NAD⁺ reduced to NADH • Lactate regeneratesNAD⁺ (oxidizes) • Glycolysis continues

  3. Lactic Acid Fermentation • Final reaction pyruvate + NADH + H⁺ → NAD⁺ + lactate • Glycolysis included glucose + 2 ADP + 2Pi → lactate + 2ATP Fermentation only produces 2 ATP!!!

  4. Anaerobic Respiration • Alcohol Fermentation • Does not occur in humans • Occurs in yeast when oxygen is not available • Facultative anaerobes • Conversion of 2 molecules of pyruvate into ethanol

  5. Alcohol Fermentation Facultative anaerobes - survive with or without oxygen • Occurs in • Bacteria, yeasts • Process • Pyruvate is decarboxylated • NAD⁺ is reduced to NADH • Produces acetaldehyde • Acetaldehyde oxidizes NADH to NAD⁺ • Ethanol is produced • Products • CO₂ • Ethanol • NAD⁺

  6. Alcohol Fermentation • Final reaction: pyruvate + NADH + H⁺ → NAD⁺ + CO₂ + ethanol • Glycolysis included (2 pyruvate molecules) glucose + 2 ADP + 2 Pi → 2 ATP + 2CO₂ + 2 ethanol Fermentation produces only 2 ATP!!!

  7. Anaerobic Respiration • Obligate anaerobes • Cannot survive in the presence of oxygen • Lack mitochondria • Have electron transport chains • Inorganic terminal electron acceptor • Sulfate SO₄²⁻ • Nitrate NO₃⁻ • Iron ion Fe³⁺ • Many prokaryotes, protists

  8. Cells that produce HEAT rather than ATP • Uncoupling • Proteins in mitochondria provide a different path for H⁺ • Instead of producing ATP, thermal energy is released • Brown adipose tissue • burns energy in order to maintain internal temperature • Hibernating mammals

  9. Alternatives to Glucose • Disaccharide carbohydrates • Hydrolyzed into glucose, fructose, galactose • Glycogen is hydrolyzed by enzymes in liver • Produce glucose-6-phosphate • Fats • Triglycerides • Hydrolyzed into glycerol • Converted into glyceraldehyde-3-phosphate • Fatty Acids • Split into 2 carbon fragments • Become acetyl groups – attach to CoA • Proteins • Hydrolyzed into amino acids • -NH₂ is removed and the rest enters as pyruvate, acetyl groups

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