Lecture 2.6 Study Guide –Fermentation Flashcards
Explain why fermentation is important to a cell under anaerobic conditions.
enable cells to get energy from glucose when O2 levels are poor/unavailable
Describe why NAD+ must be regenerated and how fermentation mechanistically accomplishes
this.
NAD+ must be regenerated to keep the glycolysis phase of fermentation pathways running. Fermentation accomplishes this by removing electrons from NADH molecules and recycles NAD+ molecules for glycolysis.
just like cellular respiration, needs a
molecule that picks up electrons. It
needs molecules of NAD+.
Without NAD+ to pick up high-energy electrons from the splitting of glucose,
glycolysis would stop.
Differentiate cellular respiration and fermentation in terms of inputs, outputs, and ATP
production.
cellular respiration—>
inputs= 1 glucose
outputs= 2 pyruvate
ATP production= 36 ATP
alcoholic (ethanol) fermentation—->
inputs= 2 pyruvate, ADP/ Pi
outputs= 2 CO2, NAD+, ethanol
ATP production= 2 ATP
lactate fermentation—->
inputs= Glucose ADP/Pi(lactic acid)
output= Lactate, ATP
ATP production= 2 ATP
Under given cellular conditions, determine whether fermentation or cellular respiration will
occur.
high O2 level —> cellular respiration
low O2 levels/no O2—> fermentation
Explain how lactic acid fermentation and alcohol fermentation allow glucose to be oxidized in
the absence of oxygen.
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Compare and contrast lactate fermentation and ethanol fermentation.
the main difference is the products of each fermentation reaction:
- Lactic acid fermentation–> makes lactic acid molecules from pyruvate
- alcoholic (ethanol) fermentation—> makes ethanol and CO2 from pyruvate.
Explain why the energy yield of glycolysis coupled to fermentation is low relative to glycolysis
coupled to cellular respiration.
fermentation is not efficient in term of energy production, the net energy production for the metabolism of glucose by glycolysis/fermentation is only 2 ATP, vs 32 ATP for aerobic respiration
Aerobic
In the presence of oxygen; requiring or using oxygen
Alcohol fermentation
in the metabolic pathway in which pyruvate from glycolysis is converted into acetaldehyde, and CO2 is released. NADH from glycolysis is used to reduce acetaldehyde to ethanol, thus regenerating NAD+ to keep glycolysis operating.
Anaerobic
means to occur in conditions lacking oxygen
Cellular respiration
The catabolic pathways by which electrons are removed from various molecules and passed through intermediate electron carriers to O2, generating H2O and releasing energy.
Electron acceptor
a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process
main electron acceptor in alcoholic fermentation: NAD+
Ethanol
the main product of alcoholic fermentation
Fermentation
aka Anaerobic respiration; the formation of ATP without oxygen
Glucose oxidation
the primary function of this process within the glycolytic pathway and the citric acid cycle is to produce NADH and FADH2, whose oxidation in the mitochondria generates ATP.
Hypoxic
a very low level of oxygen, as in an organic environment
Lactate
the deprotonated form of lactic acid
Lactic acid fermentation
A metabolic pathway in which glucose is catabolized in the absence of oxygen with the production of lactic acid.
NAD+
/NADH
this electron carrier gets reduced during glycolysis and oxidized in the CAC
Pyruvate
The ionized form of pyruvic acid, a three-carbon acid; the end product of glycolysis and the raw material for the citric acid cycle.
Redox reaction
A reaction in which one substance transfers one or more electrons to another substance
Glycolysis inputs
Glucose
NAD+
ADP/Pi
Glycolysis outputs
Pyruvate
ATP
NADH
H+
Krebs cycle inputs
Acetyl CoA ADP/Pi NAD+ FAD Water
Krebs Cycle outputs
CO2 CoA ATP NADH FADH2 H+
Oxidative phosphorylation inputs
O2
electrons from NADH
FADH2
ADP/Pi
Oxidative phosphorylation outputs
Water
ATP
FAD
NAD+
fermentation inputs
Glucose
ADP/ Pi
Lactate fermentation outputs
Lactate
ATP
Alcohol fermentation outputs
Ethanol
CO2
ATP
what must occur if oxidative phosphorylation isn’t possible due to limited O2 availability?
glycolysis must be used to generate ATP by substrate-level phosphorylation
The limiting factor for ATP production by glycolysis in a strenuously-exercising muscle that lacks lactate dehydrogenase is the supply of _____
a) O2
b) NAD+
c) ADP
d) pyruvate
e) NADH
The limiting factor for ATP production by glycolysis in a strenuously-exercising muscle that lacks lactate dehydrogenase is the supply of _____
a)
the following reaction summarizes a step in lactate fermentation. Pyrubate –> NADH + H+ —> Lactate + NAD+. What compound is oxidized and which is reduced in this reaction?
Pyruvate –> NADH + H+ —> Lactate + NAD+.
in this reaction:
oxidized (reducing agent):
reduced (oxidizing agent):
mitochondria isolates from liver cells can be used to study the rate of ETC in response to a charity of chemicals. the rate of ETC is measure as a rate of disappearance of O2 from the solution using aO2=snestove electrode
In each of the following scenarios, would the rate of O2 disappearance increase decrease, or remain the same
in each of the scenarios, the following would occur
A. increasing the pH of the mitochondrial intermembrane space _______
B. increasing the rate of pyruvate energy into the mitochondria ___
C. blocking the oxidation of FADH2 to complex 2 ____
in each of the scenarios, the following would occur
A. increasing the pH of the mitochondrial intermembrane space _______
B. increasing the rate of pyruvate energy into the mitochondria ___
C. blocking the oxidation of FADH2 to complex 2 ____
n order to distinguish between these two disorders, a physician could test the patient’s lactate levels during exercise before and after administering glycerol. What would be the expected results if this test were performed? Select all that apply.
Multiple answers:
Multiple answers are accepted for this question
Select one or more answers and submit. For keyboard navigation…SHOW MORE
a
Lactate levels would be low after intense exercise and would not increase after glycerol was administered if the patient has a deficiency in lactate dehydrogenase.
b
Lactate levels would be low after intense exercise and would increase after glycerol was administered if the patient has a deficiency in muscle PFK.
c
Lactate levels would be low after intense exercise and would not increase after glycerol was administered if the patient has a deficiency in muscle PFK.
d
Lactate levels would be low after intense exercise and would increase after glycerol was administered if the patient has a deficiency in lactate dehydrogenase.
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The anaerobic conversion of 2 glucose to 4 lactate is accompanied by a net gain of \_\_\_\_\_. Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a 0 NADH and 2 ATP. b 0 NADH and 4 ATP. c 2 NADH and 2 ATP. d 2 NADH and 4 ATP. e 4 NADH and 4 ATP.
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The fermentation of pyruvate to lactate allows glycolysis to continue in the absence of O2 because this reaction _____.
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a
produces H2O.
b
is coupled to ATP hydrolysis.
c
is coupled to ATP formation.
d
is coupled to the reduction of NAD+ to NADH.
e
is coupled to the oxidation of NADH to NAD+.
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Pyruvate is an important intermediate in carbohydrate metabolism. Which of the following is true regarding the fate of pyruvate in muscle cells?
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a
Pyruvate will be oxidized to acetyl-CoA in the presence or absence of oxygen.
b
Pyruvate will be oxidized to acetyl-CoA in the absence of oxygen or reduced to lactate in the presence of oxygen.
c
Pyruvate will be oxidized to acetyl-CoA in the presence of oxygen or reduced to lactate in the absence of oxygen.
d
Pyruvate will be reduced to acetyl-CoA in the absence of oxygen or oxidized to lactate in the presence of oxygen.
e
Pyruvate will be reduced to acetyl-CoA in the presence of oxygen or oxidized to lactate in the absence of oxygen.
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