1. Unit 2: Metabolic Processes Anaerobic Respiration
SBI4U – Ms. Richardson

2. Anaerobic Respiration
Some organisms live in anaerobic conditions
Sulfate, nitrate or carbon dioxide must be used instead as final electron acceptor
Eg: E. coli
NO3-(aq) + 2e- + 2H+  NO2-(aq) + H2O(l)

3. Fermentation
When oxygen is lacking, cells rely on glycolysis for energy
NADH needs a way to be recycled
Fermentation - process where H atoms from NADH are transferred to organic compounds other than an electron transport chain
Two types:
Ethanol fermentation
Lactate fermentation

4. Ethanol Fermentation
Facultative anaerobes – can function both aerobically and anaerobically (eg. yeast and some bacteria)
During ethanol fermentation, a CO2 molecule is removed from pyruvate
This forms acetaldehyde, the electron acceptor

5. Ethanol Fermentation - Applications
Bread
Leavened by mixing live yeast cells with starches (flour) and water
Yeast cells ferment the glucose from starch and release CO2 and ethanol
Ethanol evaporates during baking

6. Ethanol Fermentation - Applications
Alcoholic beverages
Yeast cells ferment sugars from fruit juices (wine)
Yeast cells die when ethanol concentration reaches ~12%
Gasoline
Fermentation of carbohydrate products for production of ethanol that is added to gasoline

7. Lactate Fermentation
Occurs during strenuous exercise when respiration occurs faster than oxygen can be supplied
Pyruvate is electron acceptor and is reduced to lactate (lactic acid)
Causes stiffness in muscles and fatigue
Lactate is transported through blood from muscles to liver
When oxygen levels resume, lactate is oxidized back to pyruvate

8. Lactate Fermentation
Occurs during strenuous exercise when respiration occurs faster than oxygen can be supplied
Pyruvate is electron acceptor and is reduced to lactate (lactic acid)
Causes stiffness in muscles and fatigue
Lactate is transported through blood from muscles to liver
When oxygen levels resume, lactate is oxidized back to pyruvate
The amount of oxygen needed to remove all lactate is known as the oxygen debt