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All questions of Principles of Bioenergetics (BC, GC) for MCAT Exam
The electron transport chain is an important chemical reaction of cellular respiration. What would occur if oxygen was not present in the electron transport chain (anaerobic conditions)?- a)The anaerobic reaction would be endergonic with magnitude of ΔG smaller than in the presence of oxygen.
- b)The anaerobic reaction would be exergonic with magnitude of ΔG smaller than in the presence of oxygen.
- c)The anaerobic reaction would be endergonic with magnitude of ΔG larger than in the presence of oxygen.
- d)The anaerobic reaction would be exergonic with magnitude of ΔG larger than in the presence of oxygen.
Correct answer is option 'B'. Can you explain this answer?
The electron transport chain is an important chemical reaction of cellular respiration. What would occur if oxygen was not present in the electron transport chain (anaerobic conditions)?
a)
The anaerobic reaction would be endergonic with magnitude of ΔG smaller than in the presence of oxygen.
b)
The anaerobic reaction would be exergonic with magnitude of ΔG smaller than in the presence of oxygen.
c)
The anaerobic reaction would be endergonic with magnitude of ΔG larger than in the presence of oxygen.
d)
The anaerobic reaction would be exergonic with magnitude of ΔG larger than in the presence of oxygen.
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Orion Classes answered |
In anaerobic conditions where oxygen is not present, the electron transport chain cannot proceed as usual. Without oxygen as the final electron acceptor, the electron transport chain is disrupted, leading to a buildup of electron carriers (such as NADH) and a limitation in the regeneration of electron carrier molecules.
Under anaerobic conditions, alternative pathways, such as fermentation, may be utilized to regenerate NAD+ from NADH, allowing for continued glycolysis and ATP production. However, these anaerobic pathways are generally less efficient in terms of ATP production compared to aerobic respiration.
To specifically address the question, in the absence of oxygen, the anaerobic reaction in the electron transport chain would be less exergonic compared to the reaction in the presence of oxygen.
The reaction A + B ⇆ C is an exothermic reaction; if an equilibrium mixture of A, B, and C is heated slowly, what would happen to the concentrations of each species?- a)All three concentrations decrease
- b)All three concentrations increase
- c)A and B increase, C decreases
- d)A and B decrease, C increases
Correct answer is option 'C'. Can you explain this answer?
The reaction A + B ⇆ C is an exothermic reaction; if an equilibrium mixture of A, B, and C is heated slowly, what would happen to the concentrations of each species?
a)
All three concentrations decrease
b)
All three concentrations increase
c)
A and B increase, C decreases
d)
A and B decrease, C increases
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Orion Classes answered |
An exothermic reaction produces heat as a product.
If a product of a reaction is added to an equilibrium mixture of elements of the reaction, the equilibrium will shift towards reactants.
The concentration of reactants will increase if an equilibrium mixture of A, B, and C is heated slowly.
If a product of a reaction is added to an equilibrium mixture of elements of the reaction, the equilibrium will shift towards reactants.
The concentration of reactants will increase if an equilibrium mixture of A, B, and C is heated slowly.
A flavoprotein contains one FAD moiety; if this is the only electron-acceptor in the flavoprotein, how many electrons can the flavoprotein accept when taking on its fully reduced form?- a)Two
- b)Three
- c)One
- d)Four
Correct answer is option 'A'. Can you explain this answer?
A flavoprotein contains one FAD moiety; if this is the only electron-acceptor in the flavoprotein, how many electrons can the flavoprotein accept when taking on its fully reduced form?
a)
Two
b)
Three
c)
One
d)
Four
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Anthony Moore answered |
Flavoprotein Electron Acceptance:
Flavoproteins are proteins that contain a flavin molecule as a prosthetic group. The most common flavin prosthetic groups are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). In this case, the flavoprotein contains an FAD moiety.
Electron Acceptance by FAD:
When FAD is in its fully reduced form, it can accept two electrons. This occurs through the reduction of FAD to FADH2. The two electrons are accepted sequentially, one at a time.
Electron Acceptance in Flavoprotein:
Since the FAD moiety is the only electron acceptor in the flavoprotein, it can accept a total of two electrons when it is fully reduced. This electron transfer process is crucial for the function of flavoproteins in various biological processes.
Therefore, the correct answer to the question is:
a) Two
Flavoproteins are proteins that contain a flavin molecule as a prosthetic group. The most common flavin prosthetic groups are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). In this case, the flavoprotein contains an FAD moiety.
Electron Acceptance by FAD:
When FAD is in its fully reduced form, it can accept two electrons. This occurs through the reduction of FAD to FADH2. The two electrons are accepted sequentially, one at a time.
Electron Acceptance in Flavoprotein:
Since the FAD moiety is the only electron acceptor in the flavoprotein, it can accept a total of two electrons when it is fully reduced. This electron transfer process is crucial for the function of flavoproteins in various biological processes.
Therefore, the correct answer to the question is:
a) Two
Given that nicotinamide adenine dinucleotide (NAD), in its reduced form as NADH, is a key electron-donating molecule in many metabolic reactions, which of the following is a good prediction for the standard reduction potential (E∘ of the reduction half-reaction of NAD?- a)Zero
- b)Less than zero
- c)Between zero and 1
- d)Large and positive
Correct answer is option 'B'. Can you explain this answer?
Given that nicotinamide adenine dinucleotide (NAD), in its reduced form as NADH, is a key electron-donating molecule in many metabolic reactions, which of the following is a good prediction for the standard reduction potential (E∘ of the reduction half-reaction of NAD?
a)
Zero
b)
Less than zero
c)
Between zero and 1
d)
Large and positive
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Orion Classes answered |
The standard reduction potential (E∘) is a measure of the tendency of a species to gain electrons and undergo reduction. It provides information about the electron-donating or electron-accepting ability of a molecule.
In the case of NAD, which is an electron carrier involved in oxidation-reduction reactions, the reduced form NADH donates electrons to other molecules. This means that NAD is being oxidized (losing electrons) while acting as an electron donor.
The standard reduction potential of NAD is negative because it has a tendency to donate electrons and undergo oxidation. By convention, the standard reduction potential is measured with respect to a standard hydrogen electrode (SHE), which is assigned a potential of zero. A negative standard reduction potential indicates that NAD has a lower electron-donating ability compared to the standard hydrogen electrode.
In human physiology endergonic and exergonic reaction are often coupled. How does the ATP/ADP cycle couple these reactions?
- a)Endergonic hydrolysis of ADP
- b)Exergonic phosphorylation of ADP
- c)Endergonic phosphorylation of molecule by ATP.
- d)Exergonic hydrolysis of ATP
Correct answer is option 'D'. Can you explain this answer?
In human physiology endergonic and exergonic reaction are often coupled. How does the ATP/ADP cycle couple these reactions?
a)
Endergonic hydrolysis of ADP
b)
Exergonic phosphorylation of ADP
c)
Endergonic phosphorylation of molecule by ATP.
d)
Exergonic hydrolysis of ATP
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Abigail Rodriguez answered |
Exergonic hydrolysis of ATP
The correct answer is option 'D', which states that the exergonic hydrolysis of ATP couples endergonic reactions. Let's understand why this is the case:
ATP/ADP Cycle
The ATP/ADP cycle is a fundamental process in human physiology that involves the interconversion of adenosine triphosphate (ATP) and adenosine diphosphate (ADP). ATP is often referred to as the "energy currency" of the cell because it stores and releases energy in its phosphate bonds.
Exergonic Hydrolysis of ATP
Hydrolysis of ATP involves breaking the high-energy phosphate bond, releasing energy and forming ADP and inorganic phosphate (Pi). This hydrolysis reaction is exergonic, meaning it releases energy. The energy released during ATP hydrolysis is in the form of a phosphate group, which can be used to drive endergonic reactions.
Endergonic Reactions
Endergonic reactions are energy-consuming reactions that require an input of energy to proceed. These reactions often involve the synthesis of molecules, such as the phosphorylation of a molecule by ATP.
Coupling of Reactions
The ATP/ADP cycle couples endergonic reactions with the exergonic hydrolysis of ATP. The energy released during ATP hydrolysis is used to drive endergonic reactions by transferring the released phosphate group to another molecule, a process known as phosphorylation.
When ATP is hydrolyzed to ADP and Pi, the released energy is used to phosphorylate a molecule, making it more reactive. This phosphorylation reaction is endergonic and requires an input of energy. By coupling the exergonic hydrolysis of ATP with the endergonic phosphorylation of a molecule, the energy released from ATP can be used to power energy-consuming processes in the cell.
Summary
In summary, the exergonic hydrolysis of ATP provides the energy needed to drive endergonic reactions, such as the phosphorylation of molecules. The ATP/ADP cycle allows for the continuous conversion of energy-rich ATP to ADP, releasing energy that can be used to power cellular processes.
The correct answer is option 'D', which states that the exergonic hydrolysis of ATP couples endergonic reactions. Let's understand why this is the case:
ATP/ADP Cycle
The ATP/ADP cycle is a fundamental process in human physiology that involves the interconversion of adenosine triphosphate (ATP) and adenosine diphosphate (ADP). ATP is often referred to as the "energy currency" of the cell because it stores and releases energy in its phosphate bonds.
Exergonic Hydrolysis of ATP
Hydrolysis of ATP involves breaking the high-energy phosphate bond, releasing energy and forming ADP and inorganic phosphate (Pi). This hydrolysis reaction is exergonic, meaning it releases energy. The energy released during ATP hydrolysis is in the form of a phosphate group, which can be used to drive endergonic reactions.
Endergonic Reactions
Endergonic reactions are energy-consuming reactions that require an input of energy to proceed. These reactions often involve the synthesis of molecules, such as the phosphorylation of a molecule by ATP.
Coupling of Reactions
The ATP/ADP cycle couples endergonic reactions with the exergonic hydrolysis of ATP. The energy released during ATP hydrolysis is used to drive endergonic reactions by transferring the released phosphate group to another molecule, a process known as phosphorylation.
When ATP is hydrolyzed to ADP and Pi, the released energy is used to phosphorylate a molecule, making it more reactive. This phosphorylation reaction is endergonic and requires an input of energy. By coupling the exergonic hydrolysis of ATP with the endergonic phosphorylation of a molecule, the energy released from ATP can be used to power energy-consuming processes in the cell.
Summary
In summary, the exergonic hydrolysis of ATP provides the energy needed to drive endergonic reactions, such as the phosphorylation of molecules. The ATP/ADP cycle allows for the continuous conversion of energy-rich ATP to ADP, releasing energy that can be used to power cellular processes.
ATP hydrolysis under standard biochemical conditions has ΔG < < 0, which implies which of the following about the reaction under these conditions?- a)The hydrolysis reaction decreases entropy
- b)The hydrolysis reaction is spontaneous
- c)Cleavage of the phosphoanhydride bond that occurs during hydrolysis does not require the input of energy
- d)The hydrolysis reaction is exothermic
Correct answer is option 'B'. Can you explain this answer?
ATP hydrolysis under standard biochemical conditions has ΔG < < 0, which implies which of the following about the reaction under these conditions?
a)
The hydrolysis reaction decreases entropy
b)
The hydrolysis reaction is spontaneous
c)
Cleavage of the phosphoanhydride bond that occurs during hydrolysis does not require the input of energy
d)
The hydrolysis reaction is exothermic
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Orion Classes answered |
When it is stated that ATP hydrolysis under standard biochemical conditions has ΔG << 0, it implies that the reaction is thermodynamically favorable and spontaneous. A negative ΔG indicates that the reaction releases free energy, making it energetically favorable to proceed in the forward direction.
Option A, "The hydrolysis reaction decreases entropy," is incorrect. ATP hydrolysis actually increases entropy because ATP is a high-energy molecule, and its hydrolysis leads to the production of ADP and inorganic phosphate (Pi), resulting in an increase in the total number of molecules.
Option C, "Cleavage of the phosphoanhydride bond that occurs during hydrolysis does not require the input of energy," is incorrect. ATP hydrolysis requires the input of water and catalysis by enzymes (such as ATPases) to break the phosphoanhydride bond, and it releases free energy in the process.
Option D, "The hydrolysis reaction is exothermic," is also incorrect. ATP hydrolysis is an endothermic reaction, meaning it requires the input of energy (in the form of water hydrolysis) to break the bond and release the stored energy in ATP.
Which of the following best characterizes the free energy change ΔG for an endothermic reaction under physiological conditions?- a)The sign of ΔG is negative
- b)The sign of ΔG is positive
- c)The sign of ΔG cannot be determined without more information
- d)The sign of ΔG is zero
Correct answer is option 'C'. Can you explain this answer?
Which of the following best characterizes the free energy change ΔG for an endothermic reaction under physiological conditions?
a)
The sign of ΔG is negative
b)
The sign of ΔG is positive
c)
The sign of ΔG cannot be determined without more information
d)
The sign of ΔG is zero
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Joseph Garcia answered |
Explanation:
Physiological conditions:
- Physiological conditions refer to the conditions typically found within a living organism, including temperature, pH, and concentrations of ions and molecules.
Endothermic reaction:
- An endothermic reaction is a chemical reaction that absorbs heat from its surroundings, resulting in an increase in the enthalpy of the system.
Free energy change ΔG:
- The free energy change ΔG is a measure of the spontaneity of a reaction. A negative ΔG indicates a spontaneous reaction, while a positive ΔG indicates a non-spontaneous reaction.
Characterization of ΔG for an endothermic reaction under physiological conditions:
- In the case of an endothermic reaction, the entropy term (TΔS) in the Gibbs free energy equation (ΔG = ΔH - TΔS) is positive due to the increase in entropy associated with absorbing heat.
- The sign of ΔG for an endothermic reaction under physiological conditions cannot be determined without more information because it depends on the relative magnitudes of the enthalpy change (ΔH) and the entropy change (ΔS).
- If the increase in entropy (TΔS) is greater than the increase in enthalpy (ΔH), the overall free energy change ΔG could be negative, indicating a spontaneous reaction.
- However, if the increase in enthalpy (ΔH) is greater than the increase in entropy (TΔS), the overall free energy change ΔG could be positive, indicating a non-spontaneous reaction.
Therefore, the sign of ΔG for an endothermic reaction under physiological conditions cannot be definitively determined without additional information about the specific values of ΔH and ΔS.
Physiological conditions:
- Physiological conditions refer to the conditions typically found within a living organism, including temperature, pH, and concentrations of ions and molecules.
Endothermic reaction:
- An endothermic reaction is a chemical reaction that absorbs heat from its surroundings, resulting in an increase in the enthalpy of the system.
Free energy change ΔG:
- The free energy change ΔG is a measure of the spontaneity of a reaction. A negative ΔG indicates a spontaneous reaction, while a positive ΔG indicates a non-spontaneous reaction.
Characterization of ΔG for an endothermic reaction under physiological conditions:
- In the case of an endothermic reaction, the entropy term (TΔS) in the Gibbs free energy equation (ΔG = ΔH - TΔS) is positive due to the increase in entropy associated with absorbing heat.
- The sign of ΔG for an endothermic reaction under physiological conditions cannot be determined without more information because it depends on the relative magnitudes of the enthalpy change (ΔH) and the entropy change (ΔS).
- If the increase in entropy (TΔS) is greater than the increase in enthalpy (ΔH), the overall free energy change ΔG could be negative, indicating a spontaneous reaction.
- However, if the increase in enthalpy (ΔH) is greater than the increase in entropy (TΔS), the overall free energy change ΔG could be positive, indicating a non-spontaneous reaction.
Therefore, the sign of ΔG for an endothermic reaction under physiological conditions cannot be definitively determined without additional information about the specific values of ΔH and ΔS.
Chemical reactions can be classified according to free energy changes. A chemical reaction has a ΔG of -686/kcal/mol. Is this an endergonic or exergonic reaction? How would the addition of catalyst change the ΔG this reaction?- a)Exergonic, the catalyst would reduce the ΔG.
- b)Endergonic, the catalyst would increase the ΔG.
- c)Exergonic, the catalyst would not reduce ΔG.
- d)Endergonic, the catalyst would reduce the ΔG.
Correct answer is option 'C'. Can you explain this answer?
Chemical reactions can be classified according to free energy changes. A chemical reaction has a ΔG of -686/kcal/mol. Is this an endergonic or exergonic reaction? How would the addition of catalyst change the ΔG this reaction?
a)
Exergonic, the catalyst would reduce the ΔG.
b)
Endergonic, the catalyst would increase the ΔG.
c)
Exergonic, the catalyst would not reduce ΔG.
d)
Endergonic, the catalyst would reduce the ΔG.
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Orion Classes answered |
A negative ΔG value indicates that the reaction is exergonic, meaning it releases energy. In this case, the ΔG value of -686 kcal/mol suggests that the reaction is exergonic, releasing 686 kilocalories of energy per mole of reaction.
The addition of a catalyst does not change the overall free energy change (ΔG) of a reaction. A catalyst speeds up the rate of the reaction by lowering the activation energy required for the reaction to occur. However, it does not affect the thermodynamics or the overall energy change associated with the reaction. Therefore, the addition of a catalyst would not reduce the ΔG value of -686 kcal/mol.
The symptoms of a certain disease are a result of increased competitive enzymatic inhibition. What kind of chemical manipulations with enzyme, substrate, or products would minimize the symptoms?- a)Addition of non-competitive inhibitor
- b)Decreased levels of product.
- c)Removal of an allosteric activator.
- d)Increased levels of substrate.
Correct answer is option 'D'. Can you explain this answer?
The symptoms of a certain disease are a result of increased competitive enzymatic inhibition. What kind of chemical manipulations with enzyme, substrate, or products would minimize the symptoms?
a)
Addition of non-competitive inhibitor
b)
Decreased levels of product.
c)
Removal of an allosteric activator.
d)
Increased levels of substrate.
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Orion Classes answered |
In competitive enzymatic inhibition, the symptoms of a disease are a result of an inhibitor molecule competing with the substrate for the active site of the enzyme. By increasing the levels of substrate, the aim is to overcome the inhibitory effect of the inhibitor and restore enzyme activity. With higher substrate concentrations, there will be a greater chance for substrate molecules to bind to the active site of the enzyme and outcompete the inhibitor. This can help minimize the symptoms associated with the disease by promoting the enzymatic reactions and restoring normal cellular functions.
ATP cycle refers to a set of reactions that promotes reversible changes of ATP into ADP via endergonic and exergonic reactions. According to Le Chatellier's principle, what would you expect to occur if ADP levels increased?- a)Decreased levels of ATP
- b)Decreased levels of inorganic phosphate
- c)No change in delta G
- d)Increased rate of the hydrolysis reaction
Correct answer is option 'B'. Can you explain this answer?
ATP cycle refers to a set of reactions that promotes reversible changes of ATP into ADP via endergonic and exergonic reactions. According to Le Chatellier's principle, what would you expect to occur if ADP levels increased?
a)
Decreased levels of ATP
b)
Decreased levels of inorganic phosphate
c)
No change in delta G
d)
Increased rate of the hydrolysis reaction
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Orion Classes answered |
According to Le Chatelier's principle, an increase in the concentration of one of the reactants or products in a reversible reaction will shift the equilibrium in the direction that consumes or reduces the concentration of that substance. In the case of the ATP/ADP cycle, an increase in ADP levels would favor the conversion of ADP to ATP.
The reaction ADP + Pi ⇌ ATP involves the addition of inorganic phosphate (Pi) to ADP to form ATP. If ADP levels increase, the equilibrium will shift towards the formation of ATP, consuming the excess ADP and inorganic phosphate to produce more ATP molecules. As a result, the levels of inorganic phosphate would decrease.
A reaction X is exergonic and endothermic under standard conditions; what must be true of X under these conditions?- a)Entropy increases
- b)Heat of reaction increases
- c)Entropy is constant
- d)Entropy decreases
Correct answer is option 'A'. Can you explain this answer?
A reaction X is exergonic and endothermic under standard conditions; what must be true of X under these conditions?
a)
Entropy increases
b)
Heat of reaction increases
c)
Entropy is constant
d)
Entropy decreases
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Orion Classes answered |
An exergonic reaction is a reaction that releases energy, while an endothermic reaction is a reaction that absorbs heat from its surroundings. In this case, since the reaction is exergonic, it indicates that the overall change in Gibbs free energy (ΔG) is negative, meaning the reaction is energetically favorable. However, since the reaction is endothermic, it absorbs heat, which is why it is not spontaneous under standard conditions.
When an endothermic reaction occurs, it often leads to an increase in entropy (disorder) of the system. This increase in entropy compensates for the energy input required for the reaction to proceed. Therefore, option A is correct.
Under which of the following conditions would one expect ATP hydrolysis to be non-spontaneous?- a)A very basic environment (high concentration of proton acceptors)
- b)A temperature slightly below 37 ∘
- c)No enzymes available to lower activation energy
- d)ATP concentrations very far below equilibrium concentration, and ADP concentrations very far above equilibrium concentration
Correct answer is option 'D'. Can you explain this answer?
Under which of the following conditions would one expect ATP hydrolysis to be non-spontaneous?
a)
A very basic environment (high concentration of proton acceptors)
b)
A temperature slightly below 37 ∘
c)
No enzymes available to lower activation energy
d)
ATP concentrations very far below equilibrium concentration, and ADP concentrations very far above equilibrium concentration
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Orion Classes answered |
ATP hydrolysis is typically a highly spontaneous reaction, releasing energy and driving cellular processes. However, if the concentrations of ATP are significantly lower than the equilibrium concentration and the concentrations of ADP are significantly higher than the equilibrium concentration, the reaction may not proceed spontaneously.
In a non-equilibrium state where ATP concentrations are very low and ADP concentrations are very high, the reaction would not be thermodynamically favorable because the standard free energy change (ΔG°) for ATP hydrolysis assumes equilibrium concentrations. If the concentrations deviate significantly from equilibrium, the reaction may no longer be spontaneous.
How does the free energy stored by ADP compare to the free energy stored by AMP under standard physiological conditions?- a)The free energy stored by AMP is positive and greater than the free energy stored by ADP, which is also positive
- b)The free energy stored by ADP is negative and less than the free energy stored by AMP, which is also negative
- c)The free energy stored by ADP is positive and greater than the free energy stored by AMP, which is also positive
- d)The free energy stored by ADP is positive; the free energy stored by AMP is negative
Correct answer is option 'C'. Can you explain this answer?
How does the free energy stored by ADP compare to the free energy stored by AMP under standard physiological conditions?
a)
The free energy stored by AMP is positive and greater than the free energy stored by ADP, which is also positive
b)
The free energy stored by ADP is negative and less than the free energy stored by AMP, which is also negative
c)
The free energy stored by ADP is positive and greater than the free energy stored by AMP, which is also positive
d)
The free energy stored by ADP is positive; the free energy stored by AMP is negative
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Orion Classes answered |
Under standard physiological conditions, ADP (adenosine diphosphate) and AMP (adenosine monophosphate) both store positive free energy. However, the free energy stored by ADP is greater than the free energy stored by AMP. This is because ADP has one more phosphate group than AMP, and the additional phosphate group contains high-energy bonds that contribute to the overall free energy content of the molecule.
During aerobic respiration, glucose is completely oxidized to carbon dioxide and water. Which of the following statements best describes the energy yield from the oxidation of one molecule of glucose?- a)The energy yield is 4 ATP molecules and 2 NADH molecules.
- b)The energy yield is 2 ATP molecules and 2 NADH molecules.
- c)The energy yield is 36-38 ATP molecules and 2 FADH2 molecules.
- d)The energy yield is 36-38 ATP molecules and 2 NADH molecules.
Correct answer is option 'C'. Can you explain this answer?
During aerobic respiration, glucose is completely oxidized to carbon dioxide and water. Which of the following statements best describes the energy yield from the oxidation of one molecule of glucose?
a)
The energy yield is 4 ATP molecules and 2 NADH molecules.
b)
The energy yield is 2 ATP molecules and 2 NADH molecules.
c)
The energy yield is 36-38 ATP molecules and 2 FADH2 molecules.
d)
The energy yield is 36-38 ATP molecules and 2 NADH molecules.
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Orion Classes answered |
During aerobic respiration, glucose is oxidized through glycolysis, the citric acid cycle (Krebs cycle), and the electron transport chain. These processes generate energy in the form of ATP and reduced electron carriers (NADH and FADH2). The complete oxidation of one molecule of glucose results in the production of approximately 36-38 ATP molecules through oxidative phosphorylation in the electron transport chain. Additionally, 2 FADH2 molecules are generated in the citric acid cycle.
In photosynthesis, light energy is captured by chlorophyll and converted into chemical energy. Which of the following accurately describes the relationship between light-dependent and light-independent reactions?- a)Light-dependent reactions produce ATP and NADPH, which are then used in light-independent reactions.
- b)Light-independent reactions produce ATP and NADPH, which are then used in light-dependent reactions.
- c)Light-dependent and light-independent reactions occur simultaneously and independently of each other.
- d)Light-dependent and light-independent reactions occur in the same location within the chloroplasts.
Correct answer is option 'A'. Can you explain this answer?
In photosynthesis, light energy is captured by chlorophyll and converted into chemical energy. Which of the following accurately describes the relationship between light-dependent and light-independent reactions?
a)
Light-dependent reactions produce ATP and NADPH, which are then used in light-independent reactions.
b)
Light-independent reactions produce ATP and NADPH, which are then used in light-dependent reactions.
c)
Light-dependent and light-independent reactions occur simultaneously and independently of each other.
d)
Light-dependent and light-independent reactions occur in the same location within the chloroplasts.
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Orion Classes answered |
During photosynthesis, light-dependent reactions occur in the thylakoid membranes of chloroplasts and involve the absorption of light energy by chlorophyll. In these reactions, water is split, generating oxygen, ATP, and NADPH. The ATP and NADPH produced in the light-dependent reactions are then used as energy and reducing power in the light-independent reactions (Calvin cycle), which occur in the stroma of chloroplasts. In the light-independent reactions, carbon dioxide is fixed and converted into glucose using the energy and reducing power provided by ATP and NADPH from the light-dependent reactions.
What would it mean if an antibiotic fails to distort the binding site of bacterial enzymes?- a)Increased bacterial resistance to the antibiotic.
- b)Decreased enzymatic activities on bacteria.
- c)Increased levels of substrate on bacteria.
- d)Increased activation energy of bacterial chemical reactions.
Correct answer is option 'A'. Can you explain this answer?
What would it mean if an antibiotic fails to distort the binding site of bacterial enzymes?
a)
Increased bacterial resistance to the antibiotic.
b)
Decreased enzymatic activities on bacteria.
c)
Increased levels of substrate on bacteria.
d)
Increased activation energy of bacterial chemical reactions.
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Orion Classes answered |
If an antibiotic fails to distort the binding site of bacterial enzymes, it means that the antibiotic is unable to effectively interact with and inhibit the enzymes. This can lead to increased bacterial resistance to the antibiotic. Bacteria may have mechanisms, such as mutations or changes in enzyme structure, that prevent the antibiotic from binding to the target enzyme and interfering with its activity. As a result, the bacteria are able to continue their enzymatic activities and survive the antibiotic treatment, leading to increased resistance.
What is always true of spontaneous reactions?- a)They decrease free energy
- b)They release heat
- c)They increase entropy
- d)They increase free energy
Correct answer is option 'A'. Can you explain this answer?
What is always true of spontaneous reactions?
a)
They decrease free energy
b)
They release heat
c)
They increase entropy
d)
They increase free energy
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Orion Classes answered |
Spontaneous reactions are those that occur without requiring an input of energy. One of the key characteristics of spontaneous reactions is that they tend to decrease the Gibbs free energy of the system. Gibbs free energy (ΔG) is a measure of the energy available to do work in a system, and for a spontaneous reaction, the ΔG value is negative. This means that in a spontaneous reaction, the free energy of the system decreases, indicating a more stable and energetically favorable state.
ATP hydrolysis involves the hydrolysis of what bond?- a)The phosphoanhydride bond linking the β phosphate to the α phosphate
- b)Either of the phosphorous-hydroxyl group bonds on the terminal (γ) phosphate
- c)The phosphoanhydride bond linking the γ phosphate to the β phosphate
- d)The bond linking the α phosphate to adenine
Correct answer is option 'C'. Can you explain this answer?
ATP hydrolysis involves the hydrolysis of what bond?
a)
The phosphoanhydride bond linking the β phosphate to the α phosphate
b)
Either of the phosphorous-hydroxyl group bonds on the terminal (γ) phosphate
c)
The phosphoanhydride bond linking the γ phosphate to the β phosphate
d)
The bond linking the α phosphate to adenine
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Orion Classes answered |
ATP contains high-energy phosphoanhydride bonds between its phosphate groups. During hydrolysis, the bond between the γ phosphate and the β phosphate is cleaved, resulting in the release of inorganic phosphate (Pi) and ADP (adenosine diphosphate). This hydrolysis reaction releases energy that can be utilized by cells for various biological processes.
Hemoglobin (HMB) molecules have 4 oxygen binding sites, that reversibly bind with O2 molecules. Loading HMB with an oxygen molecule creates a positive-feedback mechanism, making it easier to load subsequent molecules. In oxygen deprived tissues one molecule oxygen is released from HMB rich molecules favoring the release of the other molecules. What role is oxygen playing in these process?- a)Oxygen acts like an activator for loading, but an inhibitor for unloading.
- b)Oxygen acts like an allosteric activator.
- c)Oxygen acts like an enzyme in both process.
- d)Oxygen is a competitive inhibitor
Correct answer is option 'B'. Can you explain this answer?
Hemoglobin (HMB) molecules have 4 oxygen binding sites, that reversibly bind with O2 molecules. Loading HMB with an oxygen molecule creates a positive-feedback mechanism, making it easier to load subsequent molecules. In oxygen deprived tissues one molecule oxygen is released from HMB rich molecules favoring the release of the other molecules. What role is oxygen playing in these process?
a)
Oxygen acts like an activator for loading, but an inhibitor for unloading.
b)
Oxygen acts like an allosteric activator.
c)
Oxygen acts like an enzyme in both process.
d)
Oxygen is a competitive inhibitor
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Orion Classes answered |
In the process of oxygen binding and release in hemoglobin (Hb) molecules, oxygen acts as an allosteric activator. Allosteric regulation refers to the binding of a molecule to a site on the protein that affects the protein's activity at a different site.
When oxygen binds to one of the oxygen binding sites in Hb, it induces a conformational change in the protein structure, making it easier for subsequent oxygen molecules to bind to the remaining sites. This positive-feedback mechanism enhances the affinity of Hb for oxygen and promotes the loading of oxygen onto Hb in the lungs or oxygen-rich environment.
Conversely, in oxygen-deprived tissues, the binding of oxygen to Hb is weakened, leading to the release of oxygen from the remaining binding sites. This facilitates the unloading of oxygen to the tissues that are in need of oxygen for metabolic processes.
Why does muscle contraction result in higher body temperature?- a)Because ATP phosphorylation has negative ΔG
- b)Because ATP phosphorylation has positive ΔG
- c)Because ATP hydrolysis has negative ΔG
- d)Because ATP hydrolysis has positive ΔG
Correct answer is option 'C'. Can you explain this answer?
Why does muscle contraction result in higher body temperature?
a)
Because ATP phosphorylation has negative ΔG
b)
Because ATP phosphorylation has positive ΔG
c)
Because ATP hydrolysis has negative ΔG
d)
Because ATP hydrolysis has positive ΔG
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Orion Classes answered |
During muscle contraction, ATP is hydrolyzed to ADP and inorganic phosphate (Pi) to provide the energy needed for the contraction process. ATP hydrolysis is an exergonic reaction, meaning it releases energy. This energy is utilized by the muscles to generate force and perform work.
Some of the energy released from ATP hydrolysis is used for muscle contraction, but not all of it is converted into mechanical work. A significant portion of the energy is dissipated as heat. This increase in heat production during muscle contraction contributes to the rise in body temperature.
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MCAT Biological and Biochemical Foundations
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