fermentation h. biology ms. kim. fermentation fermentation enables some cells to produce atp without...
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Fermentation
H. BiologyMs. Kim
Fermentation• Fermentation enables some cells to
produce ATP without the use of oxygen (O2)
• Cellular respiration–Relies on oxygen to produce ATP
• In the absence of oxygen–Cells can still produce ATP through
fermentation
Cellular respiration vs. fermentationOxygen Present → Aerobic Respiration (efficient!)
Oxygen NOT Present → Fermentation (not efficient)
Respiration = 66% efficientFermentation = 3.5% efficient
Fermentation
• If there is no oxygen present (anaerobic) the pyruvate (from glycolysis) goes to fermentation
• The main goal of fermentation is:– To make NAD+ to put back into glycolysis– This makes NO ATP on its own (it just keeps
glycolysis going so that it can make 2 ATP at a time)• Occurs in the cytosol• 2 types of fermentation– 1) Alcohol– 2) Lactic acid
•Glycolysis–Can produce ATP with or
without oxygen, in aerobic or anaerobic conditions–Couples with fermentation to
produce ATP
Types of Fermentation
• Fermentation consists of–Glycolysis plus reactions that regenerate
NAD+, which can be reused by glyocolysis
Alcohol Fermentation
• Pyruvate is converted to ethanol (ethyl alcohol) in two steps, one of which releases CO2
• Ex: bacteria and yeast
• In alcohol fermentation–Pyruvate is converted to
ethanol (ethyl alcohol) in two steps, one of which releases CO2
GLUCOSE Pyruvate Ethanol and CO2
•Ex: bacteria and yeast do this
- Pyruvate is turned into ethanol- CO2 is released (bubbles!)- Done by yeast for brewing
3C Pyruvate → 2C Ethanol
Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP
Alcoholic Fermentation
Lactic Acid Fermentation
• During lactic acid fermentation–Pyruvate is reduced directly to NADH
to form lactate as a waste product–NO CO2 is released• Ex #1: fungus and bacteria in dairy industry
to make cheese/ yogurt• Ex #2: Human muscle cells
Lactic acid fermentation
- Pyruvate is turned into Lactate (or lactic acid)- Lactate is eventually
carried away by the blood to the liver where it gets converted back into pyruvate
- Example: Muscle Cells- The lactic acid is what makes your muscles sore after lifting or intensive exercise- No CO2 is released
3C Pyruvate → 3C Lactate
Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP
Lactic acid vs. alcohol fermentation
Similarities: 1. Both start with pyruvate from glycolysis 2. Both create NAD+ to be sent back to glycolysis 3. Neither make any ATP on their own
Differences: 1. Lactic acid is made and does NOT give off CO2
2. Alcohol makes ethanol and gives off CO2
Fermentation - Overview Obligate Aerobes → needs oxygen; can do respiration only
Obligate Anaerobes → can’t have oxygen; fermentation only
Facultative Anaerobes → can live with or without oxygen; prefer oxygen b/c more efficient
Respiration is 19 times more efficient than fermentation (38 ATP vs. 2 ATP)
2 ADP + 2 P1 2 ATP
GlycolysisGlucose
2 NAD+ 2 NADH2 Pyruvate
2 Acetaldehyde (gets reduced by NADH. It is
the oxidizing agent.)
2 Ethanol
(a) Alcohol fermentation2 ADP + 2 P1 2 ATP
GlycolysisGlucose
2 NAD+ 2 NADH
2 Lactate
(b) Lactic acid fermentation
H
H OH
CH3
C
O –
OC
C O
CH3
H
C O
CH3
O–
C O
C O
CH3O
C O
C OHH
CH3
CO22
NO CO2
made 2 Pyruvate (gets reduced by NADH. It is
the oxidizing agent.)
Fermentation and Cellular Respiration Compared
• Both fermentation and cellular respiration–Use glycolysis to oxidize glucose and other
organic fuels to pyruvate• Fermentation and cellular respiration– Differ in their final electron acceptor• Cell respriraition uses O2
• Fermentation uses NAD+• Cellular respiration– Produces more ATP (~36-38 ATP)
• Fermentation– Produces 2 ATP per cycle
Exit Slip1) Alcoholic fermentation converts
glucose to2) Alcoholic fermentation is
utilized by what organisms? 3) Lactic acid fermentation converts
glucose to4) Lactic acid fermentation is
utilized by what organisms? 5) What is the final acceptor for
alcoholic fermentation?6) What is the final acceptor for
lactic acid fermentation?7) What is the final acceptor for
cellular respiration?
8) Draw and label the diagram