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All questions of Krebs (citric acid) Cycle and Oxidative Phosphorylation for MCAT Exam
What is the effect of increased levels of hydrogen ions in the intermembrane space of the mitochondria?- a)Increased levels of water in intermembrane space
- b)Increased ATP production
- c)Decreased levels of oxidative phosphorylation
- d)Decreased levels of chemiosmosis
Correct answer is option 'B'. Can you explain this answer?
What is the effect of increased levels of hydrogen ions in the intermembrane space of the mitochondria?
a)
Increased levels of water in intermembrane space
b)
Increased ATP production
c)
Decreased levels of oxidative phosphorylation
d)
Decreased levels of chemiosmosis
|
Orion Classes answered |
The increased levels of hydrogen ions (protons) in the intermembrane space of the mitochondria have a direct effect on ATP production during oxidative phosphorylation. As electrons flow through the electron transport chain in the inner mitochondrial membrane, protons are pumped from the mitochondrial matrix to the intermembrane space, creating a concentration gradient of protons.
This concentration gradient drives the process of chemiosmosis, where the protons flow back into the mitochondrial matrix through ATP synthase, an enzyme complex embedded in the inner mitochondrial membrane. The movement of protons through ATP synthase powers the synthesis of ATP from ADP (adenosine diphosphate) and inorganic phosphate.
Therefore, an increased concentration of hydrogen ions in the intermembrane space leads to a steeper proton gradient, which enhances the flow of protons through ATP synthase. This increased flow of protons results in an upregulation of ATP production, as more ATP molecules are generated from ADP and inorganic phosphate.
What is the primary function of ATP synthase in oxidative phosphorylation?- a)Electron transport
- b)ATP production
- c)NADH oxidation
- d)Carbon dioxide production
Correct answer is option 'B'. Can you explain this answer?
What is the primary function of ATP synthase in oxidative phosphorylation?
a)
Electron transport
b)
ATP production
c)
NADH oxidation
d)
Carbon dioxide production
|
|
Orion Classes answered |
ATP synthase is an enzyme complex that plays a crucial role in oxidative phosphorylation. It utilizes the proton gradient generated by the electron transport chain to produce ATP from ADP and inorganic phosphate. ATP synthase acts as a molecular machine that converts the potential energy stored in the proton gradient into the chemical energy of ATP.
How do the electron transport chain and chemiosmosis affect the acidity of the intermembrane space and mitochondrial matrix?- a)The electron transport chain and chemiosmosis decrease the acidity of intermembrane space and mitochondrial matrix, respectively
- b)The electron transport chain decreases the ph of the mitochondrial matrix and chemiosmosis increases the ph of intermembrane space
- c)The electron transport chain and chemiosmosis increase the acidity of intermembrane space and mitochondrial matrix, respectively
- d)The electron transport chain does not change the ph of the mitochondrial matrix and chemiosmosis increases the acidity of intermembrane space
Correct answer is option 'C'. Can you explain this answer?
How do the electron transport chain and chemiosmosis affect the acidity of the intermembrane space and mitochondrial matrix?
a)
The electron transport chain and chemiosmosis decrease the acidity of intermembrane space and mitochondrial matrix, respectively
b)
The electron transport chain decreases the ph of the mitochondrial matrix and chemiosmosis increases the ph of intermembrane space
c)
The electron transport chain and chemiosmosis increase the acidity of intermembrane space and mitochondrial matrix, respectively
d)
The electron transport chain does not change the ph of the mitochondrial matrix and chemiosmosis increases the acidity of intermembrane space
|
|
Orion Classes answered |
During the electron transport chain, protons (hydrogen ions) are pumped from the mitochondrial matrix to the intermembrane space. This process creates a higher concentration of protons in the intermembrane space, leading to an increase in acidity or a decrease in pH. The electron transport chain transfers electrons from electron carriers, such as NADH and FADH2, to a series of protein complexes in the inner mitochondrial membrane. As electrons move through these complexes, protons are actively transported across the membrane, contributing to the buildup of protons in the intermembrane space.
Chemiosmosis, on the other hand, refers to the movement of protons back into the mitochondrial matrix through ATP synthase. This movement occurs due to the electrochemical gradient established by the electron transport chain. As protons flow through ATP synthase, ATP is synthesized. The transfer of protons from the intermembrane space to the matrix reduces the concentration of protons in the intermembrane space, leading to an increase in pH or a decrease in acidity.
Predict the outcome of a mitochondrial membrane that is more permeable to hydrogen ions than normal.- a)Reduced formation of water
- b)Reduced activity of electron transport chain
- c)Increased activity of ATP synthase
- d)Increased levels of inorganic phosphate in the mitochondrial matrix
Correct answer is option 'D'. Can you explain this answer?
Predict the outcome of a mitochondrial membrane that is more permeable to hydrogen ions than normal.
a)
Reduced formation of water
b)
Reduced activity of electron transport chain
c)
Increased activity of ATP synthase
d)
Increased levels of inorganic phosphate in the mitochondrial matrix
|
Charles Ross answered |
Increased levels of inorganic phosphate in the mitochondrial matrix:
When the mitochondrial membrane is more permeable to hydrogen ions than normal, it can disrupt the proton gradient across the inner mitochondrial membrane. This disruption can lead to an increased flow of protons back into the matrix, bypassing the ATP synthase complex. As a result, the proton motive force required for ATP synthesis is reduced, leading to decreased ATP production.
Explanation:
- The electron transport chain relies on the movement of hydrogen ions across the inner mitochondrial membrane to generate a proton motive force.
- This proton motive force is used by ATP synthase to produce ATP from ADP and inorganic phosphate.
- If the mitochondrial membrane is more permeable to hydrogen ions, there will be a leak of protons back into the matrix, reducing the proton motive force available for ATP synthesis.
- This disruption can lead to a decrease in ATP production and an accumulation of inorganic phosphate in the mitochondrial matrix.
Significance:
- Increased levels of inorganic phosphate can disrupt cellular processes that rely on ATP, as ATP is the primary energy currency of the cell.
- This disruption can affect various cellular functions, including muscle contraction, cell signaling, and biosynthetic pathways.
- Overall, the increased permeability of the mitochondrial membrane to hydrogen ions can have significant consequences for cellular energy production and homeostasis.
What products of glucose oxidation are essential for oxidative phosphorylation?- a)Acetyl CoA
- b)Pyruvate
- c)NADH and FADH2
- d)NADPH and ATP
Correct answer is option 'C'. Can you explain this answer?
What products of glucose oxidation are essential for oxidative phosphorylation?
a)
Acetyl CoA
b)
Pyruvate
c)
NADH and FADH2
d)
NADPH and ATP
|
Logan Adams answered |
Understanding Glucose Oxidation
Glucose oxidation is a critical metabolic pathway that leads to the production of energy in the form of ATP. During this process, glucose is broken down through glycolysis, the citric acid cycle, and oxidative phosphorylation.
Key Products of Glucose Oxidation
- Pyruvate: Generated during glycolysis, it is a key intermediate but is not directly involved in oxidative phosphorylation.
- Acetyl CoA: Produced from pyruvate before entering the citric acid cycle, acetyl CoA is essential for energy production but does not directly participate in oxidative phosphorylation.
- NADH and FADH2:
- These are the crucial products of glucose oxidation.
- NADH is produced during glycolysis and the citric acid cycle.
- FADH2 is generated in the citric acid cycle.
- Both NADH and FADH2 donate electrons to the electron transport chain, a series of protein complexes located in the inner mitochondrial membrane.
Role in Oxidative Phosphorylation
- Electron Transport Chain: NADH and FADH2 transfer electrons to the chain, which leads to the pumping of protons (H+) across the mitochondrial membrane.
- ATP Synthesis: This proton gradient drives ATP synthase, resulting in the conversion of ADP and inorganic phosphate into ATP, the primary energy currency of the cell.
Conclusion
In summary, among the products of glucose oxidation, NADH and FADH2 are essential for oxidative phosphorylation, as they provide the electrons necessary for the generation of ATP. Thus, option 'C' is the correct answer.
Glucose oxidation is a critical metabolic pathway that leads to the production of energy in the form of ATP. During this process, glucose is broken down through glycolysis, the citric acid cycle, and oxidative phosphorylation.
Key Products of Glucose Oxidation
- Pyruvate: Generated during glycolysis, it is a key intermediate but is not directly involved in oxidative phosphorylation.
- Acetyl CoA: Produced from pyruvate before entering the citric acid cycle, acetyl CoA is essential for energy production but does not directly participate in oxidative phosphorylation.
- NADH and FADH2:
- These are the crucial products of glucose oxidation.
- NADH is produced during glycolysis and the citric acid cycle.
- FADH2 is generated in the citric acid cycle.
- Both NADH and FADH2 donate electrons to the electron transport chain, a series of protein complexes located in the inner mitochondrial membrane.
Role in Oxidative Phosphorylation
- Electron Transport Chain: NADH and FADH2 transfer electrons to the chain, which leads to the pumping of protons (H+) across the mitochondrial membrane.
- ATP Synthesis: This proton gradient drives ATP synthase, resulting in the conversion of ADP and inorganic phosphate into ATP, the primary energy currency of the cell.
Conclusion
In summary, among the products of glucose oxidation, NADH and FADH2 are essential for oxidative phosphorylation, as they provide the electrons necessary for the generation of ATP. Thus, option 'C' is the correct answer.
Cyanide is a poison that inhibits the electron transport chain by creating a strong and stable bond with Fe – Cu center in cytochrome C oxidase (complex IV). What is the immediate consequence cyanide poisoning?- a)Prevent reduction of oxygen
- b)Prevent reduction of NADH
- c)Prevent oxidation of NADH
- d)Prevent oxidation of oxygen
Correct answer is option 'A'. Can you explain this answer?
Cyanide is a poison that inhibits the electron transport chain by creating a strong and stable bond with Fe – Cu center in cytochrome C oxidase (complex IV). What is the immediate consequence cyanide poisoning?
a)
Prevent reduction of oxygen
b)
Prevent reduction of NADH
c)
Prevent oxidation of NADH
d)
Prevent oxidation of oxygen
|
|
Orion Classes answered |
Cyanide blocks the final step of the electron transport chain, which is the transfer of electrons to oxygen (O2) by cytochrome C oxidase. By binding to the Fe-Cu center, cyanide prevents the reduction of oxygen, which is essential for the formation of water (H2O). As a result, the electron transport chain is disrupted, and oxygen cannot be utilized in the process of oxidative phosphorylation to produce ATP.
This inhibition of oxygen reduction by cyanide leads to a severe impairment of cellular respiration and the inability to generate energy in the form of ATP. The lack of ATP production can have widespread consequences on various cellular functions and can ultimately be life-threatening.
During oxidative phosphorylation, the energy required for ATP synthesis is derived from:- a)Glycolysis
- b)Krebs cycle
- c)Electron transport chain
- d)Fermentation
Correct answer is option 'C'. Can you explain this answer?
During oxidative phosphorylation, the energy required for ATP synthesis is derived from:
a)
Glycolysis
b)
Krebs cycle
c)
Electron transport chain
d)
Fermentation
|
|
Orion Classes answered |
The energy required for ATP synthesis during oxidative phosphorylation is derived from the electron transport chain. The electron transport chain is responsible for the transfer of electrons from NADH and FADH2 to oxygen, which generates a proton gradient that drives ATP synthesis.
How many molecules of acetyl CoA, an acetyl group attached to ‘coenzyme A’, are produced from a single molecule of glucose for participation in the Krebs cycle?- a)2
- b)1
- c)3
- d)4
Correct answer is option 'A'. Can you explain this answer?
How many molecules of acetyl CoA, an acetyl group attached to ‘coenzyme A’, are produced from a single molecule of glucose for participation in the Krebs cycle?
a)
2
b)
1
c)
3
d)
4
|
|
Orion Classes answered |
During glucose metabolism, a single molecule of glucose produces two molecules of pyruvate through the process of glycolysis. Each pyruvate molecule then undergoes conversion to acetyl CoA before entering the Krebs cycle. Since there are two pyruvate molecules produced from one glucose molecule, the answer is 2 molecules of acetyl CoA.
Which of the following is NOT a product of the Krebs cycle?- a)ATP
- b)NADH
- c)FADH2
- d)Carbon dioxide
Correct answer is option 'A'. Can you explain this answer?
Which of the following is NOT a product of the Krebs cycle?
a)
ATP
b)
NADH
c)
FADH2
d)
Carbon dioxide
|
|
Orion Classes answered |
Although the Krebs cycle is involved in the production of ATP indirectly through oxidative phosphorylation, ATP itself is not a direct product of the Krebs cycle. The primary products of the Krebs cycle are NADH, FADH2, and carbon dioxide.
Which of the following molecules is produced directly in the Krebs cycle?- a)NADH
- b)FADH2
- c)ATP
- d)Acetyl CoA
Correct answer is option 'A'. Can you explain this answer?
Which of the following molecules is produced directly in the Krebs cycle?
a)
NADH
b)
FADH2
c)
ATP
d)
Acetyl CoA
|
|
Orion Classes answered |
NADH is produced directly in the Krebs cycle. It is generated during the redox reactions that occur as the cycle progresses. NADH is an important electron carrier that will be used in the electron transport chain for ATP production.
High cellular concentrations of what molecule would inhibit the entry of pyruvate into the citric acid cycle?- a)Coenzyme A
- b)Pyruvate
- c)AMP
- d)NADH
Correct answer is option 'D'. Can you explain this answer?
High cellular concentrations of what molecule would inhibit the entry of pyruvate into the citric acid cycle?
a)
Coenzyme A
b)
Pyruvate
c)
AMP
d)
NADH
|
|
Orion Classes answered |
Explanation: NADH is a high-energy electron carrier that is generated during the oxidation of glucose in processes like glycolysis and the citric acid cycle. In the citric acid cycle, NADH is produced during the oxidation of isocitrate to α-ketoglutarate and during the oxidation of α-ketoglutarate to succinyl-CoA. High cellular concentrations of NADH can inhibit the entry of pyruvate into the citric acid cycle through negative feedback regulation. This occurs because the accumulation of NADH signals that the cell has sufficient energy and doesn't require further oxidation of pyruvate to generate more NADH through the citric acid cycle. As a result, the entry of pyruvate into the cycle is inhibited.
From where does the reactive oxygen species known as the superoxide anion (O2∙-) originate?- a)As a naturally occurring byproduct of multiple body processes
- b)As a product of superoxide dismutase
- c)Exogenous (outside the body) sources only
- d)As a malfunction of the electron transport chain and oxidative phosphorylation
Correct answer is option 'A'. Can you explain this answer?
From where does the reactive oxygen species known as the superoxide anion (O2∙-) originate?
a)
As a naturally occurring byproduct of multiple body processes
b)
As a product of superoxide dismutase
c)
Exogenous (outside the body) sources only
d)
As a malfunction of the electron transport chain and oxidative phosphorylation
|
|
Orion Classes answered |
The superoxide anion is produced as a byproduct of various metabolic processes within the body. These processes include oxidative phosphorylation in the mitochondria, enzymatic reactions, and cellular respiration. During these processes, electrons can be incompletely transferred, leading to the formation of the superoxide anion. Additionally, certain enzymes, such as NADPH oxidase, can generate superoxide as part of their normal function. It is important to note that while the superoxide anion is a reactive oxygen species and can have damaging effects, the body has defense mechanisms, including antioxidant enzymes, to neutralize and manage the levels of reactive oxygen species.
What cellular conditions favor increased activity of the electron transport chain and oxidative phosphorylation?- a)High ADP concentrations
- b)High NAD+ concentrations
- c)Low NADH concentrations
- d)Low oxygen concentrations
Correct answer is option 'A'. Can you explain this answer?
What cellular conditions favor increased activity of the electron transport chain and oxidative phosphorylation?
a)
High ADP concentrations
b)
High NAD+ concentrations
c)
Low NADH concentrations
d)
Low oxygen concentrations
|
|
Orion Classes answered |
The activity of the electron transport chain and oxidative phosphorylation is closely linked to the cellular energy demands. When the cell requires more ATP, the electron transport chain and oxidative phosphorylation are stimulated. One of the key factors influencing their activity is the concentration of ADP (adenosine diphosphate). ADP is converted to ATP through the phosphorylation process in oxidative phosphorylation. When ADP levels are high, it indicates that ATP levels are low, signaling a need for increased ATP production. This stimulates the electron transport chain to transfer electrons and generate a proton gradient, which in turn drives ATP synthesis. Therefore, high ADP concentrations favor increased activity of the electron transport chain and oxidative phosphorylation.
Which of the following inhibits oxidative phosphorylation by blocking the flow of electrons in the electron transport chain?- a)Cyanide
- b)Acetyl CoA
- c)Pyruvate
- d)ATP
Correct answer is option 'A'. Can you explain this answer?
Which of the following inhibits oxidative phosphorylation by blocking the flow of electrons in the electron transport chain?
a)
Cyanide
b)
Acetyl CoA
c)
Pyruvate
d)
ATP
|
|
Orion Classes answered |
Cyanide inhibits oxidative phosphorylation by blocking the flow of electrons in the electron transport chain. It binds to complex IV, preventing the transfer of electrons to oxygen and ultimately halting ATP synthesis.
In oxidative phosphorylation, the energy released during electron transport is used to:- a)Pump protons across the inner mitochondrial membrane.
- b)Convert ADP to ATP.
- c)Oxidize NADH to NAD+.
- d)Reduce oxygen to water.
Correct answer is option 'B'. Can you explain this answer?
In oxidative phosphorylation, the energy released during electron transport is used to:
a)
Pump protons across the inner mitochondrial membrane.
b)
Convert ADP to ATP.
c)
Oxidize NADH to NAD+.
d)
Reduce oxygen to water.
|
|
Orion Classes answered |
In oxidative phosphorylation, the energy released during electron transport is utilized to generate ATP. The proton gradient established across the inner mitochondrial membrane drives the synthesis of ATP by ATP synthase, which converts ADP (adenosine diphosphate) to ATP (adenosine triphosphate).
Which electron carrier would have the greatest negative impact on ATP production during oxidative phosphorylation if its production was inhibited?- a)NADH
- b)Oxygen
- c)FADH2
- d)Water
Correct answer is option 'A'. Can you explain this answer?
Which electron carrier would have the greatest negative impact on ATP production during oxidative phosphorylation if its production was inhibited?
a)
NADH
b)
Oxygen
c)
FADH2
d)
Water
|
|
Orion Classes answered |
NADH is a key electron carrier in the electron transport chain, and it plays a critical role in the generation of ATP through oxidative phosphorylation. NADH transfers electrons to the electron transport chain, which creates a proton gradient across the inner mitochondrial membrane. This proton gradient is then utilized by ATP synthase to produce ATP.
If the production of NADH is inhibited, there would be a reduced supply of electrons entering the electron transport chain. As a result, the generation of the proton gradient would be compromised, leading to a decrease in ATP production. Since NADH is a major contributor to the electron flow and proton gradient generation, its inhibition would have the greatest negative impact on ATP production during oxidative phosphorylation.
With respect to their relative pH, how do the cytosol, intermembrane space of the mitochondria, and the mitochondrial matrix compare?- a)pH of mitochondrial matrix < pH of cytosol = pH of intermembrane space
- b)pH of mitochondrial matrix > pH of cytosol > pH of intermembrane space
- c)pH of cytosol > pH of intermembrane space = pH of mitochondrial matrix
- d)pH of intermembrane space < pH of mitochondrial matrix < pH of cytosol
Correct answer is option 'B'. Can you explain this answer?
With respect to their relative pH, how do the cytosol, intermembrane space of the mitochondria, and the mitochondrial matrix compare?
a)
pH of mitochondrial matrix < pH of cytosol = pH of intermembrane space
b)
pH of mitochondrial matrix > pH of cytosol > pH of intermembrane space
c)
pH of cytosol > pH of intermembrane space = pH of mitochondrial matrix
d)
pH of intermembrane space < pH of mitochondrial matrix < pH of cytosol
|
|
Orion Classes answered |
The relative pH levels of the cytosol, intermembrane space of the mitochondria, and the mitochondrial matrix differ. The mitochondrial matrix has a higher pH than both the cytosol and the intermembrane space. This is because the electron transport chain and chemiosmosis during oxidative phosphorylation lead to the pumping of protons from the mitochondrial matrix to the intermembrane space. This creates a higher concentration of protons and a lower pH in the intermembrane space compared to the mitochondrial matrix. The protons then flow back into the mitochondrial matrix through ATP synthase, which leads to the synthesis of ATP. This process results in a higher concentration of protons and a lower pH in the intermembrane space compared to the mitochondrial matrix. Finally, the cytosol, which is outside the mitochondria, typically has a higher pH than both the intermembrane space and the mitochondrial matrix.
Which complex of the electron transport chain directly transfers electrons to oxygen?- a)Complex I
- b)Complex II
- c)Complex III
- d)Complex IV
Correct answer is option 'D'. Can you explain this answer?
Which complex of the electron transport chain directly transfers electrons to oxygen?
a)
Complex I
b)
Complex II
c)
Complex III
d)
Complex IV
|
|
Orion Classes answered |
Complex IV, also known as cytochrome c oxidase, directly transfers electrons to oxygen. It is the final complex of the electron transport chain and facilitates the reduction of oxygen to water.
How are electrons extracted from the citric acid cycle for use in the electron transport chain?- a)Reduction of ATP and GTP
- b)Reduction of NAD+ and FAD
- c)Oxidation of NAD+ and FAD
- d)Oxidation of ATP and GTP
Correct answer is option 'B'. Can you explain this answer?
How are electrons extracted from the citric acid cycle for use in the electron transport chain?
a)
Reduction of ATP and GTP
b)
Reduction of NAD+ and FAD
c)
Oxidation of NAD+ and FAD
d)
Oxidation of ATP and GTP
|
|
Orion Classes answered |
During the citric acid cycle, the oxidation of acetyl CoA leads to the production of reducing equivalents in the form of NADH and FADH2. These molecules carry high-energy electrons that are extracted from the citric acid cycle and then delivered to the electron transport chain (ETC). NAD+ and FAD act as electron carriers and are reduced to NADH and FADH2, respectively, by accepting the electrons generated during the cycle. These reduced forms of NAD and FAD then donate the electrons to the ETC for further energy generation.
Which molecule is responsible for shuttling electrons between complex III and complex IV in the electron transport chain?- a)NADH
- b)FADH2
- c)Cytochrome c
- d)Ubiquinone
Correct answer is option 'C'. Can you explain this answer?
Which molecule is responsible for shuttling electrons between complex III and complex IV in the electron transport chain?
a)
NADH
b)
FADH2
c)
Cytochrome c
d)
Ubiquinone
|
|
Orion Classes answered |
Cytochrome c is responsible for shuttling electrons between complex III and complex IV in the electron transport chain. It is a small protein that carries electrons from complex III to complex IV, facilitating the final step of ATP synthesis.
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