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Goals and Objectives• Identify verbally and in written form the steps
involved in fermentation.• Identify verbally and in written form the
factors that influence fermentation.• Compare and contrast fermentation and
cellular respiration
Status Check• Define a redox reaction.• Define “oxidation” & “reduction”
(remember The Lion King)• What is the chemical equation for cellular
respiration?• In cellular respiration, what is oxidized and
what is reduced?• What are the three major steps in cellular
respiration?• What is NAD+ used for in cellular respiration?
Cellular Respiration ReviewC6H12O6 + 6 O2 6 CO2 + 6 H2O + energy
• Exergonic reaction, spontaneous, -ΔG, energy released• Electrons moves from carbon in glucose to oxygen• Glucose turns into CO2; O2 turns into H2O
• Electrons are carried throughout the reaction by NAD+ • Glycolysis will always happen• Krebs Cycle and Oxidative Phosphorylation will only
occur if O2 is present
What is Fermentation?• Occurs when O2 is not present (anaerobic
reaction)• Involves glycolysis (only step that does not
need O2)• Allows the organism to keep producing small
amounts of ATP without O2 as a final e- acceptor
• Some bacteria use some form of fermentation as main source of ATP
Glycolysis In-Depth C6H12O6 2 C3H4O3 (pyruvate)+ energy (2 ATP)
• Glucose is split into 2 pyruvate molecules• Net gain of 2 ATP created (energy)• e- transferred from glucose to NAD+• Problem: if no O2, all NAD+ gets used up!!!!
2 e-, 4 H+
2 NAD+ 2 NADH + H+
Fermentation In-Depth• Goal of fermentation is to keep glycolysis going, producing 2 ATP
• In order for glycolysis to happen, need constant supply of NAD+ (e- acceptor)
• e- given back to pyruvate from NADH to form lactate, NAD+ renewed
Lactic Acid Fermentation (Humans)
Gain e-
Lose e-
NAD+ able to go back to glycolysis
*As long as NAD+ is available, glycolysis can still happen!!
Transported to liver, converted back to pyruvate
*Too much lactic acid build-up causes muscle fatigue
Alcohol Fermentation (Beer)•Found in some bacteria and fungi
•Same principle as Lactic Acid Fermentation (make NAD+ to keep glycolysis going)
•End product is ethanol (ethyl alcohol)
•CO2 gas is produced (ex. yeast in bread)
• Both ethanol and CO2 are waste products
In General…
NAD+ + 2 H+ NADH + H+ NAD+ + 2 H+ Glycolysis Fermentation
Gain e- from glucose, NAD+ reduced to NADH
Lose e- to pyruvate,NADH oxidized to NAD+
• Glycolysis reduces NAD+ to make NADH
• Fermentation oxidizes NADH to make NAD+
Decisions, decisions…
• Presence of O2 determines steps after glycolysis
• Fermentation can switch to cellular respiration once [O2] is sufficient
Cell. Res. Vs. Fermentation• Cell Respiration
– Produces massive amounts of ATP (~38 ATP)
– Needs O2
– Thought to have evolved after fermentation.
– Final e- acceptor is O2
• Fermentation– Produces little ATP (only
2 ATP through glycolysis)– Does not need O2
– Thought to have evolved first.
– Final e- acceptor is pyurvate
Question 2• In fermentation, the electrons from NADH are
given to:A) LactateB) GlucoseC) AlcoholD) Pyruvate
Question 3
• After fermentation, lactate is:A) Turned into glucoseB) Turned into pyruvateC) Turned into alcoholD) Turned into fatty acid
Question 4• In fermentation,
A) NADH is oxidized to NAD+B) NAD+ is oxidized to NADHC) NADH is reduced to NAD+D) NAD+ is reduced to NADH
Question 5
• In fermentation,A) Pyruvate is oxidized, NADH reducedB) Pyruvate is reduced, NADH oxidizedC) Lactate is oxidized, NADH reducedD) Lactate is reduced, NADH oxidized