Organic Chemistry, Biochemistry, and Metabolism - MCAT Biological and Biochemical Foundations of Living Systems
Card 0 of 2928
During cellular respiration, where is NADH produced?
During cellular respiration, where is NADH produced?
NADH is produced during glycolysis, which occurs in the cytoplasm. NADH is also produced during the Krebs cycle, which occurs in the mitochondrial matrix. The protons generated in the production of NADH are later used in the intermembrane space to power ATP synthase during oxidative phosphorylation.
NADH is produced during glycolysis, which occurs in the cytoplasm. NADH is also produced during the Krebs cycle, which occurs in the mitochondrial matrix. The protons generated in the production of NADH are later used in the intermembrane space to power ATP synthase during oxidative phosphorylation.
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If the Krebs cycle is overstimulated, the body will produce too much of which of the following molecules?
If the Krebs cycle is overstimulated, the body will produce too much of which of the following molecules?
Of the answer choices, only carbon dioxide is a product of the Krebs cycle. If the cycle is overstimulated, too much of the products will be formed and the body will have too much carbon dioxide.
Glucose is the reactant that fuels glycolysis to produce pyruvate, which is then converted to acetyl CoA for the Krebs cycle. As such, each of these would be depleted as reactants fueling an overstimulation of the Krebs cycle.
Of the answer choices, only carbon dioxide is a product of the Krebs cycle. If the cycle is overstimulated, too much of the products will be formed and the body will have too much carbon dioxide.
Glucose is the reactant that fuels glycolysis to produce pyruvate, which is then converted to acetyl CoA for the Krebs cycle. As such, each of these would be depleted as reactants fueling an overstimulation of the Krebs cycle.
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Where is the Krebs cycle carried out in eukaryotic cells?
Where is the Krebs cycle carried out in eukaryotic cells?
During the Krebs cycle, or citric acid cycle, acetyl CoA is oxidized to CO2 and NAD+ and FADH are reduced to NADH and FADH2, respectively. This process is carried out in the mitochondrial matrix of eukaryotic cells.
The electron transport chain is carried out in the inner membrane of the mitochondria, while glycolysis is carried out in the cytosol.
During the Krebs cycle, or citric acid cycle, acetyl CoA is oxidized to CO2 and NAD+ and FADH are reduced to NADH and FADH2, respectively. This process is carried out in the mitochondrial matrix of eukaryotic cells.
The electron transport chain is carried out in the inner membrane of the mitochondria, while glycolysis is carried out in the cytosol.
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Cellular respiration is the set of metabolic reactions that occur in cells to produce energy in the form of ATP. During cellular respiration, high energy intermediates are created that can then be oxidized to make ATP. During what stage are these intermediates produced?
Cellular respiration is the set of metabolic reactions that occur in cells to produce energy in the form of ATP. During cellular respiration, high energy intermediates are created that can then be oxidized to make ATP. During what stage are these intermediates produced?
The citric acid (Krebs) cycle and glycolysis yield high energy intermediates that can then be used to make ATP. Each turn of the citric acid cycle generates NADH and FADH2, and each cycle of glycolysis generates NADH. These intermediates can then donate their electrons and become oxidized in the electron transport chain. Production of these electron donors is essential to the function of the electron transport chain.
The citric acid (Krebs) cycle and glycolysis yield high energy intermediates that can then be used to make ATP. Each turn of the citric acid cycle generates NADH and FADH2, and each cycle of glycolysis generates NADH. These intermediates can then donate their electrons and become oxidized in the electron transport chain. Production of these electron donors is essential to the function of the electron transport chain.
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Acetyl-CoA is a react in the citric acid cycle, while 
and 
are products. If twelve molecules of 
are produced over a period of time, how many 
molecules are produced during this period?
Acetyl-CoA is a react in the citric acid cycle, while
Each turn of the citric acid cycle is powered by one molecule of acetyl-CoA, resulting in three 
and one 
. The net reaction is:
Since twelve 
are produced, there must have been an input of four acetyl-CoA molecules and four total turns in the cycle. As a result, four 
molecules were produced.
Each turn of the citric acid cycle is powered by one molecule of acetyl-CoA, resulting in three
Since twelve
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Which statement is false regarding the citric acid cycle?
Which statement is false regarding the citric acid cycle?
Oxygen is needed for the electron transport chain to occur which oxidizes 
and 
. If there is no oxygen available then Krebs cycle would not occur since there would be no oxidized electron carriers. Therefore oxygen is only indirectly required for the Krebs cycle to occur, not directly.
Oxygen is needed for the electron transport chain to occur which oxidizes
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James took a neural sample and separated the cell body from the axon. He noticed that when he placed both parts on a glucose plate, the cell body began releasing carbon dioxide. What could explain the result?
James took a neural sample and separated the cell body from the axon. He noticed that when he placed both parts on a glucose plate, the cell body began releasing carbon dioxide. What could explain the result?
The cell body of a neuron is where the mitochondria and all other organelles are located. Recall from the Krebs cycle that carbon dioxide is produced as a byproduct. Anaerobic respiration, which occurs in the cytoplasm does not release carbon dioxide (in humans) and produces lactic acid instead. Note that in certain organisms like yeast, fermentation produces ethanol (two-carbons) and carbon dioxide since pyruvate, the product of glycolysis is a three-carbon molecule.
The cell body of a neuron is where the mitochondria and all other organelles are located. Recall from the Krebs cycle that carbon dioxide is produced as a byproduct. Anaerobic respiration, which occurs in the cytoplasm does not release carbon dioxide (in humans) and produces lactic acid instead. Note that in certain organisms like yeast, fermentation produces ethanol (two-carbons) and carbon dioxide since pyruvate, the product of glycolysis is a three-carbon molecule.
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In which of the following places does the breakdown phase of beta-oxidation occur?
In which of the following places does the breakdown phase of beta-oxidation occur?
Beta-oxidation is the metabolization of fatty acids to generate acetyl CoA, which can be used in the Krebs cycle. This process always occurs in the mitochondrial matrix.
Beta-oxidation is the metabolization of fatty acids to generate acetyl CoA, which can be used in the Krebs cycle. This process always occurs in the mitochondrial matrix.
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The process of glycolysis is used by all cells of the body to turn glucose into ATP for cellular energy. When stores of glucose are low, however, the body can break down a form of stored glucose in the liver to increase glucose reserves. The supply of glycogen is limited, and eventually the body must break down free fatty acids (FFAs) through a process called beta-oxidation.
Which organ in the body cannot perform beta-oxidation, thus requiring the use of ketone bodies when stores of glucose are depleted?
The process of glycolysis is used by all cells of the body to turn glucose into ATP for cellular energy. When stores of glucose are low, however, the body can break down a form of stored glucose in the liver to increase glucose reserves. The supply of glycogen is limited, and eventually the body must break down free fatty acids (FFAs) through a process called beta-oxidation.
Which organ in the body cannot perform beta-oxidation, thus requiring the use of ketone bodies when stores of glucose are depleted?
The brain is unable to perform beta-oxidation of free fatty acids in the event of a prolonged fasting state. It is important to know this aspect of metabolism. In a fasting state, the liver beta-oxidizes free fatty acids into ketone bodies for the brain to use. Additionally, when energy demands are high, muscles can break down fat for additional ATP.
Unlike other organs in the body, the heart relies almost entirely on beta-oxidation for its energy needs.
The brain is unable to perform beta-oxidation of free fatty acids in the event of a prolonged fasting state. It is important to know this aspect of metabolism. In a fasting state, the liver beta-oxidizes free fatty acids into ketone bodies for the brain to use. Additionally, when energy demands are high, muscles can break down fat for additional ATP.
Unlike other organs in the body, the heart relies almost entirely on beta-oxidation for its energy needs.
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The process of glycolysis is used by all cells of the body to turn glucose into ATP for cellular energy. When stores of glucose are low, however, the body can break down a form of stored glucose in the liver to increase glucose reserves. The supply of glycogen is limited, and eventually the body must break down free fatty acids (FFAs) through a process called beta-oxidation.
What is the end-product of beta-oxidation?
The process of glycolysis is used by all cells of the body to turn glucose into ATP for cellular energy. When stores of glucose are low, however, the body can break down a form of stored glucose in the liver to increase glucose reserves. The supply of glycogen is limited, and eventually the body must break down free fatty acids (FFAs) through a process called beta-oxidation.
What is the end-product of beta-oxidation?
Free fatty acids are chains of acetyl-CoA molecules linked together. When a free fatty acid undergoes beta-oxidation, it is returned to its component parts of acetyl-CoA. It is important to know that free fatty acids cannot be used to make glucose; they can only be fed into the Krebs cycle.
Free fatty acids are chains of acetyl-CoA molecules linked together. When a free fatty acid undergoes beta-oxidation, it is returned to its component parts of acetyl-CoA. It is important to know that free fatty acids cannot be used to make glucose; they can only be fed into the Krebs cycle.
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Which of the following describes a beta oxidation reaction?
Which of the following describes a beta oxidation reaction?
Beta oxidation is the process by which fatty acid molecules are broken down in the mitochondria to produce acetyl-coA, which can then enter the citric acid (Krebs) cycle. The correct transition from reactant to product for beta oxidation is fatty acid to acetyl-CoA.
Beta oxidation is the process by which fatty acid molecules are broken down in the mitochondria to produce acetyl-coA, which can then enter the citric acid (Krebs) cycle. The correct transition from reactant to product for beta oxidation is fatty acid to acetyl-CoA.
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Fatty acids and cholesterol are stored in tissues as                      and                     , respectively.
Fatty acids and cholesterol are stored in tissues as                      and                     , respectively.
Fatty acids are stored as triacylglycerols in adipose tissue, while cholesterol is stored as cholesteryl esters in a number of different tissues. Both fatty acids and cholesterol are hydrophobic molecules, which is why they are stored as lipid droplets within their respective tissues.
Fatty acids are stored as triacylglycerols in adipose tissue, while cholesterol is stored as cholesteryl esters in a number of different tissues. Both fatty acids and cholesterol are hydrophobic molecules, which is why they are stored as lipid droplets within their respective tissues.
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The cellular membrane is a very important structure. The lipid bilayer is both hydrophilic and hydrophobic. The hydrophilic layer faces the extracellular fluid and the cytosol of the cell. The hydrophobic portion of the lipid bilayer stays in between the hydrophobic regions like a sandwich. This bilayer separation allows for communication, protection, and homeostasis.
One of the most utilized signaling transduction pathways is the G protein-coupled receptor pathway. The hydrophobic and hydrophilic properties of the cellular membrane allows for the peptide and other hydrophilic hormones to bind to the receptor on the cellular surface but to not enter the cell. This regulation allows for activation despite the hormone’s short half-life. On the other hand, hydrophobic hormones must have longer half-lives to allow for these ligands to cross the lipid bilayer, travel through the cell’s cytosol and eventually reach the nucleus.
Cholesterol allows the lipid bilayer to maintain its fluidity despite the fluctuation in the body’s temperature due to events such as increasing metabolism. Cholesterol binds to the hydrophobic tails of the lipid bilayer. When the temperature is low, the cholesterol molecules prevent the hydrophobic tails from compacting and solidifying. When the temperature is high, the hydrophobic tails will be excited and will move excessively. This excess movement will bring instability to the bilayer. Cholesterol will prevent excessive movement.
Which of the following hormones utilizes cholesterol as a precursor?
I. Cortisol
II. Aldosterone
III. Mineralocorticoid
The cellular membrane is a very important structure. The lipid bilayer is both hydrophilic and hydrophobic. The hydrophilic layer faces the extracellular fluid and the cytosol of the cell. The hydrophobic portion of the lipid bilayer stays in between the hydrophobic regions like a sandwich. This bilayer separation allows for communication, protection, and homeostasis.
One of the most utilized signaling transduction pathways is the G protein-coupled receptor pathway. The hydrophobic and hydrophilic properties of the cellular membrane allows for the peptide and other hydrophilic hormones to bind to the receptor on the cellular surface but to not enter the cell. This regulation allows for activation despite the hormone’s short half-life. On the other hand, hydrophobic hormones must have longer half-lives to allow for these ligands to cross the lipid bilayer, travel through the cell’s cytosol and eventually reach the nucleus.
Cholesterol allows the lipid bilayer to maintain its fluidity despite the fluctuation in the body’s temperature due to events such as increasing metabolism. Cholesterol binds to the hydrophobic tails of the lipid bilayer. When the temperature is low, the cholesterol molecules prevent the hydrophobic tails from compacting and solidifying. When the temperature is high, the hydrophobic tails will be excited and will move excessively. This excess movement will bring instability to the bilayer. Cholesterol will prevent excessive movement.
Which of the following hormones utilizes cholesterol as a precursor?
I. Cortisol
II. Aldosterone
III. Mineralocorticoid
Both cortisol and aldosterone are synthesized in the adrenal cortex with cholesterol as the precursor. Mineralocorticoid refers aldosterone, which is also secreted by the adrenal cortex. All of these hormones are steroidal, which means they are derived from cholesterol. Other steroid hormones are the sex hormones.
Both cortisol and aldosterone are synthesized in the adrenal cortex with cholesterol as the precursor. Mineralocorticoid refers aldosterone, which is also secreted by the adrenal cortex. All of these hormones are steroidal, which means they are derived from cholesterol. Other steroid hormones are the sex hormones.
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The process of glycolysis is used by all cells of the body to turn glucose into ATP for cellular energy. When stores of glucose are low, however, the body can break down a form of stored glucose in the liver to increase glucose reserves.
What molecule is broken down by a phosphorylase in the liver to yield glucose-1-phosphate?
The process of glycolysis is used by all cells of the body to turn glucose into ATP for cellular energy. When stores of glucose are low, however, the body can break down a form of stored glucose in the liver to increase glucose reserves.
What molecule is broken down by a phosphorylase in the liver to yield glucose-1-phosphate?
Glycogen is the polymer form of glucose, stored in the liver and other tissues when glucose is abundant. When glucose levels are high, glucose-1-phosphate is assembled into branching chains of glycogen. When glucose levels fall, glycogen is broken down by glycogen phosphorylase back into glucose-1-phosphate units. These monomers can be used in glycolysis and cellular respiration. Glycogen is the first source of energy that is used when glucose stores are low.
Glycogen is the polymer form of glucose, stored in the liver and other tissues when glucose is abundant. When glucose levels are high, glucose-1-phosphate is assembled into branching chains of glycogen. When glucose levels fall, glycogen is broken down by glycogen phosphorylase back into glucose-1-phosphate units. These monomers can be used in glycolysis and cellular respiration. Glycogen is the first source of energy that is used when glucose stores are low.
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The body attempts to maintain a steady concentration of glucose in the blood, promoting consistent brain function and red blood cell survival. When glucose levels fall, however, the body breaks down glycogen to replenish stores for a short period of time before new glucose molecules are made through the process of gluconeogenesis.
In which organ does gluconeogenesis occur?
The body attempts to maintain a steady concentration of glucose in the blood, promoting consistent brain function and red blood cell survival. When glucose levels fall, however, the body breaks down glycogen to replenish stores for a short period of time before new glucose molecules are made through the process of gluconeogenesis.
In which organ does gluconeogenesis occur?
Gluconeogenesis, the process of creating new glucose from precursors, occurs in the liver and to a very small extent in the cortex of the kidney. The largest stores of glycogen are also located in the liver, but become quickly depleted in situations of low blood glucose.
Gluconeogenesis, the process of creating new glucose from precursors, occurs in the liver and to a very small extent in the cortex of the kidney. The largest stores of glycogen are also located in the liver, but become quickly depleted in situations of low blood glucose.
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When the body is unable to renew its glucose stores through glycogenolysis and gluconeogenesis, it makes ketone bodies derived from beta-oxidation of free fatty acids. Which of the following is not a ketone body utilized by the brain during periods of starvation?
When the body is unable to renew its glucose stores through glycogenolysis and gluconeogenesis, it makes ketone bodies derived from beta-oxidation of free fatty acids. Which of the following is not a ketone body utilized by the brain during periods of starvation?
The three ketone bodies utilized by the body are acetoacetate, beta-hydroxybutyrate, and acetone. These are produced from acetyl-CoA during beta-oxidation. Acetyl-CoA undergoes conversion reactions to the three ketone bodies in the liver.
Even if you did not know the names of the ketone bodies, you should know that aldehyde is not a ketone because its carbonyl moiety does not have carbons connected from both sides to the carbonyl carbon.
The three ketone bodies utilized by the body are acetoacetate, beta-hydroxybutyrate, and acetone. These are produced from acetyl-CoA during beta-oxidation. Acetyl-CoA undergoes conversion reactions to the three ketone bodies in the liver.
Even if you did not know the names of the ketone bodies, you should know that aldehyde is not a ketone because its carbonyl moiety does not have carbons connected from both sides to the carbonyl carbon.
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Which of the following is not an adequate alternative energy source for humans?
Which of the following is not an adequate alternative energy source for humans?
Carbohydrates can be stored as glycogen in the liver, fats can be stored as triglycerides or fatty acids in adipose tissue, and proteins can be made into alpha-keto acids. Hence, all of these are forms of energy storage that can be used as alternative energy sources.
Cellulose is a polysaccharide that is found in plants. Humans cannot digest cellulose due to its beta-glycosidic linkages.
Carbohydrates can be stored as glycogen in the liver, fats can be stored as triglycerides or fatty acids in adipose tissue, and proteins can be made into alpha-keto acids. Hence, all of these are forms of energy storage that can be used as alternative energy sources.
Cellulose is a polysaccharide that is found in plants. Humans cannot digest cellulose due to its beta-glycosidic linkages.
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Which of the following cannot be directly converted to acetyl-CoA?
Which of the following cannot be directly converted to acetyl-CoA?
Pyruvate can be converted to acetyl-CoA by decarboxylation. Beta oxidation can convert fatty acids to acetyl-CoA. Transaminases can be used to make alpha-keto acids, which can be converted to acetyl-coA. Glucose cannot be directly converted to acetyl-CoA; it must be transformed into pyruvate first.
Pyruvate can be converted to acetyl-CoA by decarboxylation. Beta oxidation can convert fatty acids to acetyl-CoA. Transaminases can be used to make alpha-keto acids, which can be converted to acetyl-coA. Glucose cannot be directly converted to acetyl-CoA; it must be transformed into pyruvate first.
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The transformation of compound B to compound C below is known as what type of reaction?
The transformation of compound B to compound C below is known as what type of reaction?
The conversion of compound B to compound Cresults in the elimination of water, which, by definition, is a dehydration reaction. The hydroxyl group on compound B is protonated by the sulfuric acid, generating an 
leaving group and allowing the formation of the alkene product in compound C.
Hydroboration is the oxidation of an alkene with a borohydride (usually sodium borohydride) reagent, to produce an alkane. Hydration involves the use of a water reactant, usually producing an alcohol product. Hydrogenation is the oxidation of alkene double bonds with the use of a palladium interface to produce an alkane product. Decarboxylation results in product carbon dioxide from a carboxylic acid or carbonic anhydrase reactant.
The conversion of compound B to compound Cresults in the elimination of water, which, by definition, is a dehydration reaction. The hydroxyl group on compound B is protonated by the sulfuric acid, generating an
Hydroboration is the oxidation of an alkene with a borohydride (usually sodium borohydride) reagent, to produce an alkane. Hydration involves the use of a water reactant, usually producing an alcohol product. Hydrogenation is the oxidation of alkene double bonds with the use of a palladium interface to produce an alkane product. Decarboxylation results in product carbon dioxide from a carboxylic acid or carbonic anhydrase reactant.
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Which alcohol will react most rapidly via an SN1 mechanism?
Which alcohol will react most rapidly via an SN1 mechanism?
Tertiary alcohols react most rapidly via SN1 mechanisms because they form stable tertiary carbocations. Primary and secondary alcohols typically react most rapidly via SN2 mechanisms.
Of the available options, 
is the only one that contains a tertiary alcohol.
Tertiary alcohols react most rapidly via SN1 mechanisms because they form stable tertiary carbocations. Primary and secondary alcohols typically react most rapidly via SN2 mechanisms.
Of the available options,
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