6.13 fermentation
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6.13 Fermentation. Fermentation is an anaerobic (without oxygen) energy-generating process It takes advantage of glycolysis, producing two ATP molecules and reducing NAD + to NADH The trick is to oxidize the NADH without passing its electrons through the electron transport chain to oxygen. - PowerPoint PPT PresentationTRANSCRIPT
6.13 Fermentation
• Fermentation is an anaerobic (without oxygen) energy-generating process – It takes advantage of glycolysis, producing two ATP
molecules and reducing NAD+ to NADH– The trick is to oxidize the NADH without passing its
electrons through the electron transport chain to oxygen
6.13 Fermentation
• Most cellular respiration requires O2 to produce ATP
• Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions)
• In the absence of O2, glycolysis couples with fermentation or anaerobic respiration to produce ATP
6.13 Lactic Acid Fermentation
• Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation– NADH is oxidized to NAD+ when pyruvate is reduced
to lactate– Pyruvate is serving as a place to dispose of the
electrons generated in glycolysis
– Products: 2 NAD+, lactic acid, 2ATP(from glycolysis)– Can be added to milk to make cheese…..how?
Glucose
NADH
NAD+
2
2
NADH2
NAD+2
2 ADPP
ATP2
2 Pyruvate
2 Lactate
GLY
CO
LYSI
S
Lactic acid fermentation
2
6.13 Fermentation enables cells to produce ATP without oxygen
• The baking and wine-making industry have used alcohol fermentation for thousands of years– Yeasts are single-celled fungi that not only can use
respiration for energy but can ferment under anaerobic conditions
– They convert pyruvate to CO2 and ethanol while oxidizing NADH back to NAD+
– Products: ethyl alcohol, 2CO2 , 2 NAD+, 2ATP– Can be added to grapes to make wine….how?
2 ADPP
ATP2 GLY
CO
LYSI
S
NADH
NAD+
2
2
NADH2
NAD+2
2 Pyruvate
2 Ethanol
Alcohol fermentation
Glucose
CO22released
2
• Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2
• Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration
So there are 2 choices for facultative anaerobes…
Fig. 9-19Glucose
Glycolysis
Pyruvate
CYTOSOL
No O2 present:Fermentation
O2 present: Aerobic cellular respiration
MITOCHONDRIONAcetyl CoAEthanol
orlactate
Citricacidcycle
Regulation of Cellular Respiration via Feedback Mechanisms
• Feedback inhibition is the most common mechanism for control
• If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down
• Control of catabolism is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway
You should now be able to:
1. Explain in general terms how redox reactions are involved in energy exchanges
2. Name the three stages of cellular respiration; for each, state the region of the eukaryotic cell where it occurs and the products that result
3. In general terms, explain the role of the electron transport chain in cellular respiration
4. Explain where and how the respiratory electron transport chain creates a proton gradient
5. Distinguish between fermentation and anaerobic respiration
6. Distinguish between obligate and facultative anaerobes