In the absence of oxygen, the net yield of ATP from one molecule of glucose drastically decreases. Which of the following best explains why this occurs in eukaryotic cells?

The electron transport chain stops, preventing the recycling of NAD^{+} through oxidative phosphorylation and halting the Krebs cycle.

The cell switches to fermentation, which utilizes the electron transport chain but uses an organic molecule as the final electron acceptor.

Glycolysis is inhibited because the enzyme phosphofructokinase requires oxygen as a co-factor to catalyze the phosphorylation of fructose-6-phosphate.

Pyruvate is converted directly into FADH_{2} in the cytosol, which provides much less energy than the NADH produced during aerobic respiration.

If a yeast cell is shifted from an aerobic environment to an anaerobic environment while maintaining the same rate of ATP consumption, how must the rate of glucose utilization change?

The rate of glucose utilization must increase significantly because the ATP yield per glucose molecule drops from approximately 30-32 to 2.

The rate of glucose utilization must increase because anaerobic respiration requires the input of oxygen atoms from the glucose molecule to produce water.

The rate of glucose utilization remains constant because the cell can produce the same amount of ATP through substrate-level phosphorylation in the Krebs cycle.

The rate of glucose utilization decrease because the cell enters a state of dormancy to conserve energy in the absence of oxygen.

Which of the following describes the immediate fate of electrons in the mitochondrial matrix if a cell is suddenly deprived of O_{2} ?

Electrons remain associated with NADH and FADH_{2} because the electron transport chain can no longer pass them to a final acceptor.

Electrons are diverted to the protein ATP synthase, which reverses its function to pump protons out of the matrix.

Electrons are transferred to H_{2}O to form superoxide radicals, which then inhibit the enzymes of the Krebs cycle.

Electrons are used to reduce pyruvate to glucose-6-phosphate in an effort to store energy for later use.

When a human muscle cell is deprived of O_{2} during intense exercise, it relies on lactic acid fermentation to continue producing ATP. What is the primary biological purpose of converting pyruvate to lactate in this process?

To regenerate NAD^{+} so that glycolysis can continue to produce ATP through substrate-level phosphorylation.

To allow the cell to transport pyruvate into the mitochondria where it can be used in the Krebs cycle without oxygen.

To produce a small amount of ATP directly through the reduction of pyruvate.

To produce additional CO_{2} that can be used to buffer the pH of the cytoplasm.

In an experiment, mitochondria are isolated and placed in a buffer containing ADP, inorganic phosphate, and a source of electrons (NADH). If the solution is purged of all dissolved oxygen ( O_{2} ), which of the following best predicts the effect on the proton gradient and ATP synthesis?

The proton gradient will dissipate as the electron transport chain stops, leading to a cessation of ATP synthesis by ATP synthase.

The Krebs cycle will accelerate to compensate for the lack of oxygen, maintaining the proton gradient through substrate-level phosphorylation.

ATP synthesis will continue unchanged because the mitochondria will switch to using CO_{2} as the final electron acceptor.

The proton gradient will increase because protons will no longer be used to form water, leading to a surge in ATP production.

If a chemical inhibitor is introduced that prevents the conversion of pyruvate to lactate during anaerobic conditions in muscle cells, what would be the most likely effect on ATP production?

ATP production would stop almost completely because NAD^{+} would not be regenerated, eventually halting glycolysis.

ATP production would increase because the energy normally lost as heat during lactate formation would be diverted to ATP synthase.

ATP production would remain the same because the cell would simply switch to ethanol fermentation instead.

ATP production would increase because the cell would be forced to use the Krebs cycle without oxygen.

An obligate aerobic bacterium is moved to a completely anaerobic environment. Which of the following best predicts the immediate impact on the H^{+} concentration in the intermembrane space and the subsequent effect on ATP production?

The H^{+} concentration will decrease, causing the chemiosmotic gradient to collapse and ATP synthase to stop producing ATP.

The H^{+} concentration will increase, leading to an over-activation of ATP synthase and a temporary surge in ATP production.

The H^{+} concentration will remain constant, but ATP production will stop because oxygen is a direct reactant required by the ATP synthase enzyme.

The H^{+} concentration will decrease, but ATP production will increase as the bacterium shifts to using its stored lactic acid for energy.

Which of the following describes the most likely impact on the pH of the mitochondrial intermembrane space when a cell is shifted from an aerobic to an anaerobic environment?

The pH will increase because the electron transport chain stops pumping protons into the intermembrane space.

The pH will increase because the lack of oxygen prevents the formation of H_{2}O , which is naturally acidic.

The pH will remain neutral because the cell will immediately compensate by increasing the rate of the Krebs cycle.

The pH will decrease because the accumulation of NADH in the matrix forces protons into the intermembrane space.

Which of the following stoichiometric changes best describes the metabolic transition in a facultative anaerobic cell if its oxygen supply is cut off, assuming the cell maintains a constant rate of ATP demand?

The molar ratio of glucose consumed to ATP produced increases from approximately 1:30 to 1:2 .

The molar ratio of NAD^{+} to NADH in the cytosol increases due to the cessation of oxidative phosphorylation.

The molar ratio of ATP produced to glucose consumed remains constant because substrate-level phosphorylation is independent of the electron transport chain.

The molar ratio of CO_{2} produced per glucose molecule increases as the cell shifts to the fermentation pathway.

In a laboratory experiment, a suspension of mitochondria is provided with NADH and ADP . If the supply of dissolved oxygen is completely exhausted, which of the following best predicts the change in the mitochondrial matrix concentration of NAD^{+} and its effect on ATP production?

The concentration of NAD^{+} will decrease, leading to the cessation of the Krebs cycle and a stop in oxidative phosphorylation.

The concentration of NAD^{+} will decrease, but ATP production will increase because the energy from NADH is diverted directly to substrate-level phosphorylation.

The concentration of NAD^{+} will increase as the mitochondria attempt to compensate for the lack of oxygen by accelerating the link reaction.

The concentration of NAD^{+} will remain constant because the cell will switch to using FAD as the terminal electron acceptor for the electron transport chain.

Predict effect of oxygen absence on ATP production

Predict effect of oxygen absence on ATP production | Quizalize

Q 1/10
Score 0
In the absence of oxygen, the net yield of ATP from one molecule of glucose drastically decreases. Which of the following best explains why this occurs in eukaryotic cells?
30
The electron transport chain stops, preventing the recycling of $NAD^{+}$ through oxidative phosphorylation and halting the Krebs cycle.
The cell switches to fermentation, which utilizes the electron transport chain but uses an organic molecule as the final electron acceptor.
Glycolysis is inhibited because the enzyme phosphofructokinase requires oxygen as a co-factor to catalyze the phosphorylation of fructose-6-phosphate.
Pyruvate is converted directly into $FADH_{2}$ in the cytosol, which provides much less energy than the $NADH$ produced during aerobic respiration.
Q 2/10
Score 0
If a yeast cell is shifted from an aerobic environment to an anaerobic environment while maintaining the same rate of ATP consumption, how must the rate of glucose utilization change?
30
The rate of glucose utilization must increase because anaerobic respiration requires the input of oxygen atoms from the glucose molecule to produce water.
The rate of glucose utilization remains constant because the cell can produce the same amount of ATP through substrate-level phosphorylation in the Krebs cycle.
The rate of glucose utilization decrease because the cell enters a state of dormancy to conserve energy in the absence of oxygen.
The rate of glucose utilization must increase significantly because the ATP yield per glucose molecule drops from approximately 30-32 to 2.

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