Unit 2 - Alternative Pathways Flashcards
Anaerobic pathway:
-When O2 is lacking, cells rely on glycolysis for energy
Anaerobic Pathway: PROBLEM
The cell will run out of NAD+
Anaerobic Pathway: THEREFORE
NADH needs a way to be recycled
Anaerobic Pathway: FERMENTATION
process where H atoms from NADH r transferred to organic compounds other than an electron transport chain (Oxidizes NADH back to NAD+)
two types of fermentation
1) ethanol fermentation
2) lactate fermentation
Lactic Acid Fermentation
oxygen is not present
- conversion of 2 mols of pyruvate into lactic acid when O2 is not present
- happens during vigorous muscle exercise
- liver converts lactic acid back into glucose
Lactic Acid Fermentation: Occurs in HUMANS when…
demand for ATP exceeds the rate at which oxygen can be supplied
Lactic Acid Fermentation:
Process
- pyruvate is converted into lactate
- NAD+ reduced to NADH
- lactate regenerates NAD+ (Oxidizes)
- glycolysis continues
Lactic Acid Fermentation: Final rxn
pyruvate + NADH + H = NAD + lactate
Glycolysis includes
2 pyruvate mols
- glucose + 2ADP +2pi =2 lactate + 2 ATP
- fermentation only produces 2 ATP
a) lactic acid fermentation occurs in humans
Applications of Lactic Acid
- occurs during strenuous exercises when respiration occurs faster than oxygen can be supplied
- burning sensation felt in muscles
- transported through blood from muscles to liver
- O2 levels resume, lactate is oxidized back to pyruvate
Oxygen debt
amount of oxygen needed to remove all lactate
Alcohol Fermentation
- not in humans
- occurs in bacteria and yeast when oxygen is not available
- conversion of 2 mols of pyruvate into 2 ethanol
Facultative anaerobes
can function both aerobically and anaerobically (ie. yeast and some bacteria)
Alcohol Fermentation Process (4)
- pyruvate is decarboxylated
- produces acetaldehyde
- acetaldehyde oxidizes NADH to NAD+
- ethanol is produced
Alcohol Fermentation Products
- CO2
- Ethanol
- NAD+
Alcohol Fermentation final rxn
pyruvate + NADH + H = NAD + CO2 + ethanol
alcohol fermentation glycolysis include
glucose + 2 ADP + 2Pi = 2CO2 + 2 ethanol
fermentation produces only 2 ATP
Ethanol fermentation application (3)
1) bread
2) alcoholic beverages
3) gasoline
BREAD
- leavened by mixing live yeast cells w starches (flour) and water
- yeast cells ferment the glucose from starch and release CO2 and ethanol
- ethanol evaporates during baking
ALCOHOLIC BEVERAGES
-yeast cells ferment sugars from fruit juices (WINE)
-yeast cells die when ethanol concentrations reaches 12%
GASOLINE
-fermentation of carbohydrate products for the production of ethanol that is added to gasoline
Obligate Anaerobes
- cannot survive in the presence of oxygen
- no mitochondria
- contain ETC
- many prokaryotes and protists
Obligate Anaerobes: ETC
take place on specialized membranes use another inorganic compound as a final electron acceptor instead of oxygen.
ie. NO3, FE3, SO42-
where do we find these organisms?
- soils deep underground and in the sediments of marshes, wetlands, and lake
- rotten egg smell in some wetlands r produced by anaerobic sulphur-reducing bacteria and use SO42- as the terminal electron acceptor
