Anaerobic Pathways - 4.5

Q: What do organisms that use an organic molecule as an electron acceptor undergo?

A: Fermentation

Q: Do these organisms still go through glycolysis?

Like aerobic organisms, these species still go

through glycolysis

• However, they need other molecules to carry the reaction forward

• Most notably NAD+

Q: What do they need to carry the reaction forward?

A: Other molecules, most notably NAD⁺

Q: Why does fermentation occur?

A: To regenerate NAD⁺

Q: What are the two types of fermentation?

A: Alcohol fermentation and lactate fermentation

Q: What happens in alcohol fermentation?

A: Pyruvate is decarboxylated; CO₂, NAD⁺, and ethanol are produced

Q: What happens in lactate fermentation?

A: Pyruvate reacts with NADH, converts to lactate, and NAD⁺ is produced

Q: Where is alcohol fermentation commonly found?

A: Yeast and bacteria

Q: What are the steps of alcohol fermentation?

Steps:

• Pyruvate is decarboxylated to form

acetaldehyde

• Acetaldehyde oxides NADH

• Produces CO2, Ethanol, NAD+

Q: What is the overall formula of alcohol fermentation?

glucose + 2ADP + Pi →2ATP + 2CO2 + 2 ethanol

Uses of Alcohol Fermentation 

Baking and Beer/Wine Production

Baking

• Yeast helps make bread dough grow

• Yeast is mixed with sugar

• Yeast converts sugar into ethanol and CO₂

• CO₂ expands and creates gas bubbles

• High temperatures evaporate alcohol and CO₂ disperses

Beer and Wine Production

• Cultivated yeasts can produce alcohol

• Overripe or rotting fruit produce alcohol

• Birds or insects that eat these foods may become too intoxicated

Q: How much ATP does fermentation produce?

A: 2 ATP

Q: How much ATP does aerobic respiration produce?

A: 38 ATP

Q: Why is fermentation less efficient?

A: Because of alcohol; is a by-product that uses lots of energy

Q: Where is lactate fermentation used?

A: Primary energy pathway for some bacteria, and in humans

Q: Where does lactate fermentation occur in humans?

A: In muscle cells, after strenuous activity

Q: Why does lactate fermentation occur in humans?

• We have a demand for ATP that exceeds the rate of O2

  supply

  • To maximize ATP production, glycolysis occurs rapidly

Q: What happens to excess pyruvate?

A: Converts to lactate

Q: What is a side effect of lactate accumulation?

A: Can increase muscle soreness