Molecular Properties - MCAT Biological and Biochemical Foundations of Living Systems
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Which intermolecular force accounts for the fact that alcohols have higher boiling points than alkanes?
Which intermolecular force accounts for the fact that alcohols have higher boiling points than alkanes?
Hydrogen bonding occurs when the hydrogen atom attached to an electronegative atom of one molecule (in an alcohol, this electronegative atom is oxygen) becomes attracted to an electronegative atom of a different molecule (either oxygen, nitrogen, or fluorine). This attractive force is so strong that it significantly increases the boiling point of the alcohol.
Hydrogen bonding occurs when the hydrogen atom attached to an electronegative atom of one molecule (in an alcohol, this electronegative atom is oxygen) becomes attracted to an electronegative atom of a different molecule (either oxygen, nitrogen, or fluorine). This attractive force is so strong that it significantly increases the boiling point of the alcohol.
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Prions are the suspected cause of a wide variety of neurodegenerative diseases in mammals. According to prevailing theory, prions are infectious particles made only of protein and found in high concentrations in the brains of infected animals. All mammals produce normal prion protein, PrPC, a transmembrane protein whose function remains unclear.
Infectious prions, PrPRes, induce conformational changes in the existing PrPC proteins according to the following reaction:
PrPC + PrPRes → PrPRes + PrPRes
The PrPRes is then suspected to accumulate in the nervous tissue of infected patients and cause disease. This model of transmission generates replicated proteins, but does so bypassing the standard model of the central dogma of molecular biology. Transcription and translation apparently do not play a role in this replication process.
This theory is a major departure from previously established biological dogma. A scientist decides to test the protein-only theory of prion propagation. He establishes his experiment as follows:
Homogenized brain matter of infected rabbits is injected into the brains of healthy rabbits, as per the following table:
Rabbit 1 and 2: injected with normal saline on days 1 and 2
The above trials serve as controls.
Rabbit 3 and 4: injected with homogenized brain matter on days 1 and 2
The above trials use unmodified brain matter.
Rabbit 5 and 6: injected with irradiated homogenized brain matter on days 1 and 2
The above trials use brain matter that has been irradiated to destroy nucleic acids in the homogenate.
Rabbit 7 and 8: injected with protein-free centrifuged homogenized brain matter on days 1 and 2
The above trials use brain matter that has been centrifuged to generate a protein-free homogenate and a protein-rich homogenate based on molecular weight.
Rabbit 9 and 10: injected with boiled homogenized brain matter on days 1 and 2
The above trials use brain matter that have been boiled to destroy any bacterial contaminants in the homogenate.
A scientist claims that he has discovered how PrPRes propagates. He claims that the PrPRes interacts with the PrPC by using its own partially negative oxygen atoms to interact with partially positive hydrogen atoms on PrPC. What is true of these bonds?
Prions are the suspected cause of a wide variety of neurodegenerative diseases in mammals. According to prevailing theory, prions are infectious particles made only of protein and found in high concentrations in the brains of infected animals. All mammals produce normal prion protein, PrPC, a transmembrane protein whose function remains unclear.
Infectious prions, PrPRes, induce conformational changes in the existing PrPC proteins according to the following reaction:
PrPC + PrPRes → PrPRes + PrPRes
The PrPRes is then suspected to accumulate in the nervous tissue of infected patients and cause disease. This model of transmission generates replicated proteins, but does so bypassing the standard model of the central dogma of molecular biology. Transcription and translation apparently do not play a role in this replication process.
This theory is a major departure from previously established biological dogma. A scientist decides to test the protein-only theory of prion propagation. He establishes his experiment as follows:
Homogenized brain matter of infected rabbits is injected into the brains of healthy rabbits, as per the following table:
Rabbit 1 and 2: injected with normal saline on days 1 and 2
The above trials serve as controls.
Rabbit 3 and 4: injected with homogenized brain matter on days 1 and 2
The above trials use unmodified brain matter.
Rabbit 5 and 6: injected with irradiated homogenized brain matter on days 1 and 2
The above trials use brain matter that has been irradiated to destroy nucleic acids in the homogenate.
Rabbit 7 and 8: injected with protein-free centrifuged homogenized brain matter on days 1 and 2
The above trials use brain matter that has been centrifuged to generate a protein-free homogenate and a protein-rich homogenate based on molecular weight.
Rabbit 9 and 10: injected with boiled homogenized brain matter on days 1 and 2
The above trials use brain matter that have been boiled to destroy any bacterial contaminants in the homogenate.
A scientist claims that he has discovered how PrPRes propagates. He claims that the PrPRes interacts with the PrPC by using its own partially negative oxygen atoms to interact with partially positive hydrogen atoms on PrPC. What is true of these bonds?
Hydrogen bonds are an example of the strongest type of intermolecular bonds. They are, however, still intermolecular, and thus always weaker than covalent bonds.
Hydrogen bonds are an example of the strongest type of intermolecular bonds. They are, however, still intermolecular, and thus always weaker than covalent bonds.
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Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma.
Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts.
She sets up the following experiment:
As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.
A scientist is conducting a follow up experiment to the one described above. She is attempting to determine how cryptosporidium adheres to the gastrointestinal mucosa. She determines that the key step is a binding of a surface protein ligand to a receptor. Which of the following forces are common patterns for protein-protein interaction?
I. Hydrogen bonding
II. Coordinate covalent bonding
III. Polar covalent
IV. Metallic bonding
Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma.
Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts.
She sets up the following experiment:
As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.
A scientist is conducting a follow up experiment to the one described above. She is attempting to determine how cryptosporidium adheres to the gastrointestinal mucosa. She determines that the key step is a binding of a surface protein ligand to a receptor. Which of the following forces are common patterns for protein-protein interaction?
I. Hydrogen bonding
II. Coordinate covalent bonding
III. Polar covalent
IV. Metallic bonding
Of the choices listed, only hydrogen bonds would be very common among protein-protein bonds. Covalent bonds are strong and permanent, and so are uncommon between macromolecules. Some proteins form disulfide bridges, or covalent bonds between sulfur atoms intra-molecularly, but inter-molecularly covalent interactions are usually not appropriate.
Of the choices listed, only hydrogen bonds would be very common among protein-protein bonds. Covalent bonds are strong and permanent, and so are uncommon between macromolecules. Some proteins form disulfide bridges, or covalent bonds between sulfur atoms intra-molecularly, but inter-molecularly covalent interactions are usually not appropriate.
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One component of the immune system is the neutrophil, a professional phagocyte that consumes invading cells. The neutrophil is ferried to the site of infection via the blood as pre-neutrophils, or monocytes, ready to differentiate as needed to defend their host.
In order to leave the blood and migrate to the tissues, where infection is active, the monocyte undergoes a process called diapedesis. Diapedesis is a process of extravasation, where the monocyte leaves the circulation by moving in between endothelial cells, enters the tissue, and matures into a neutrophil.
Diapedesis is mediated by a class of proteins called selectins, present on the monocyte membrane and the endothelium. These selectins interact, attract the monocyte to the endothelium, and allow the monocytes to roll along the endothelium until they are able to complete diapedesis by leaving the vasculature and entering the tissues.
The image below shows monocytes moving in the blood vessel, "rolling" along the vessel wall, and eventually leaving the vessel to migrate to the site of infection.

Which of the following is likely true about the interactions between selectins and the "rolling" monocytes?
One component of the immune system is the neutrophil, a professional phagocyte that consumes invading cells. The neutrophil is ferried to the site of infection via the blood as pre-neutrophils, or monocytes, ready to differentiate as needed to defend their host.
In order to leave the blood and migrate to the tissues, where infection is active, the monocyte undergoes a process called diapedesis. Diapedesis is a process of extravasation, where the monocyte leaves the circulation by moving in between endothelial cells, enters the tissue, and matures into a neutrophil.
Diapedesis is mediated by a class of proteins called selectins, present on the monocyte membrane and the endothelium. These selectins interact, attract the monocyte to the endothelium, and allow the monocytes to roll along the endothelium until they are able to complete diapedesis by leaving the vasculature and entering the tissues.
The image below shows monocytes moving in the blood vessel, "rolling" along the vessel wall, and eventually leaving the vessel to migrate to the site of infection.
Which of the following is likely true about the interactions between selectins and the "rolling" monocytes?
The interactions that give rise to the neutrophil rolling phenomenon are likely the product of intermolecular bonds, such as hydrogen bonds, that often do not require full ionic charges to be present.
Additionally, proteins and carbohydrates are the typical mediators of these interactions, not fatty acids, and they usually form quickly, reversibly, and spontaneously, without the help of local enzymes.
The interactions that give rise to the neutrophil rolling phenomenon are likely the product of intermolecular bonds, such as hydrogen bonds, that often do not require full ionic charges to be present.
Additionally, proteins and carbohydrates are the typical mediators of these interactions, not fatty acids, and they usually form quickly, reversibly, and spontaneously, without the help of local enzymes.
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Type 1 diabetes is a well-understood autoimmune disease. Autoimmune diseases result from an immune system-mediated attack on one’s own body tissues. In normal development, an organ called the thymus introduces immune cells to the body’s normal proteins. This process is called negative selection, as those immune cells that recognize normal proteins are deleted. If cells evade this process, those that recognize normal proteins enter into circulation, where they can attack body tissues. The thymus is also important for activating T-cells that recognize foreign proteins.
As the figure below shows, immune cells typically originate in the bone marrow. Some immune cells, called T-cells, then go to the thymus for negative selection. Those that survive negative selection, enter into general circulation to fight infection. Other cells, called B-cells, directly enter general circulation from the bone marrow. It is a breakdown in this carefully orchestrated process that leads to autoimmune disease, such as type 1 diabetes.

In the process of negative selection described in the passage, the interaction of T-cells and normal body proteins happens via brief and easily broken biochemical bonds. What type of bonding is most probably involved?
Type 1 diabetes is a well-understood autoimmune disease. Autoimmune diseases result from an immune system-mediated attack on one’s own body tissues. In normal development, an organ called the thymus introduces immune cells to the body’s normal proteins. This process is called negative selection, as those immune cells that recognize normal proteins are deleted. If cells evade this process, those that recognize normal proteins enter into circulation, where they can attack body tissues. The thymus is also important for activating T-cells that recognize foreign proteins.
As the figure below shows, immune cells typically originate in the bone marrow. Some immune cells, called T-cells, then go to the thymus for negative selection. Those that survive negative selection, enter into general circulation to fight infection. Other cells, called B-cells, directly enter general circulation from the bone marrow. It is a breakdown in this carefully orchestrated process that leads to autoimmune disease, such as type 1 diabetes.
In the process of negative selection described in the passage, the interaction of T-cells and normal body proteins happens via brief and easily broken biochemical bonds. What type of bonding is most probably involved?
Hydrogen bonding is characteristic of a great deal of the intermolecular interactions seen in biochemical systems. Ionic and covalent bonding are far too permanent, and T-cells would never escape the thymus were these bonding patterns the principal interactions. Ionic and covalent interactions generally represent intramolecular interactions, while intermolecular interactions are more temporary. Common intermolecular forces are hydrogen bonding, dipole interactions, and van der Waals forces. (Note that hydrogen bonding can also be an intramolecular interaction for certain molecular structures).
Hydrogen bonding is characteristic of a great deal of the intermolecular interactions seen in biochemical systems. Ionic and covalent bonding are far too permanent, and T-cells would never escape the thymus were these bonding patterns the principal interactions. Ionic and covalent interactions generally represent intramolecular interactions, while intermolecular interactions are more temporary. Common intermolecular forces are hydrogen bonding, dipole interactions, and van der Waals forces. (Note that hydrogen bonding can also be an intramolecular interaction for certain molecular structures).
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Which compound has the largest bond energy between carbons?
Which compound has the largest bond energy between carbons?
It helps to remember that bond energy is inversely proportional to bond length. In other words, the shorter the bond, the higher the bond energy.
Bond length is shortened when pi bonds are involved, so double and triple bonds are much shorter than simple sigma bonds. The bond length between the carbons in ethyne is the shortest out of all options because they are triple bonded to one another. This also makes it the most stable bond, and gives it the largest bond energy.
Benzene and 1,3-butadiene will have relatively high energy stored in double bonds, but will be unable to match a triple bond. Propane has only single bonds and will have the lowest bond energy of these answers.
It helps to remember that bond energy is inversely proportional to bond length. In other words, the shorter the bond, the higher the bond energy.
Bond length is shortened when pi bonds are involved, so double and triple bonds are much shorter than simple sigma bonds. The bond length between the carbons in ethyne is the shortest out of all options because they are triple bonded to one another. This also makes it the most stable bond, and gives it the largest bond energy.
Benzene and 1,3-butadiene will have relatively high energy stored in double bonds, but will be unable to match a triple bond. Propane has only single bonds and will have the lowest bond energy of these answers.
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Drain cleaners are a common household staple, used to open clogged drains in bathtubs and sinks. Human hair is a common culprit that clogs pipes, and hair is made predominately of protein. Drain cleaners are effective at breaking down proteins that have accumulated in plumbing. Drain cleaners can be either acidic or basic, and are also effective at breaking down fats that have accumulated with proteins.
A typical reaction—reaction 1—which would be expected for a drain cleaner on contact with human hair, would be as follows in an aqueous solution:
Another reaction that may occur, reaction 2, would take place as follows in an aqueous solution:
The C–N bond in the original protein, before reaction with drain cleaner is .
Drain cleaners are a common household staple, used to open clogged drains in bathtubs and sinks. Human hair is a common culprit that clogs pipes, and hair is made predominately of protein. Drain cleaners are effective at breaking down proteins that have accumulated in plumbing. Drain cleaners can be either acidic or basic, and are also effective at breaking down fats that have accumulated with proteins.
A typical reaction—reaction 1—which would be expected for a drain cleaner on contact with human hair, would be as follows in an aqueous solution:
Another reaction that may occur, reaction 2, would take place as follows in an aqueous solution:
The C–N bond in the original protein, before reaction with drain cleaner is .
The C–N bond is a single bond, and the carbonyl bond is a double bond. Double bonds are stronger and shorter than single bonds.
The C–N bond is a single bond, and the carbonyl bond is a double bond. Double bonds are stronger and shorter than single bonds.
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Drain cleaners a common household staple, used to open clogged drains in bathtubs and sinks. Human hair is a common culprit that clogs pipes, and hair is made predominately of protein. Drain cleaners are effective at breaking down proteins that have accumulated in plumbing. Drain cleaners can be either acidic or basic, and are also effective at breaking down fats that have accumulated with proteins.
A typical reaction—reaction 1—which would be expected for a drain cleaner on contact with human hair, would be as follows in an aqueous solution:
Another reaction that may occur, reaction 2, would take place as follows in an aqueous solution:
In the carbonyl bonds of the preceeding passage .
Drain cleaners a common household staple, used to open clogged drains in bathtubs and sinks. Human hair is a common culprit that clogs pipes, and hair is made predominately of protein. Drain cleaners are effective at breaking down proteins that have accumulated in plumbing. Drain cleaners can be either acidic or basic, and are also effective at breaking down fats that have accumulated with proteins.
A typical reaction—reaction 1—which would be expected for a drain cleaner on contact with human hair, would be as follows in an aqueous solution:
Another reaction that may occur, reaction 2, would take place as follows in an aqueous solution:
In the carbonyl bonds of the preceeding passage .
The carbon at the center of a carbonyl group bonds with three sigma bonds, and one pi bond. The pi bond exists above and below the plane of the sigma bond. This carbon thus shows sp2 hybridization.
The carbon at the center of a carbonyl group bonds with three sigma bonds, and one pi bond. The pi bond exists above and below the plane of the sigma bond. This carbon thus shows sp2 hybridization.
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Which organelle would have the most negative effect if its membrane were damaged?
Which organelle would have the most negative effect if its membrane were damaged?
The lysosomes contain an acidic environment and digestive enzymes. Damage to the membrane would allow hydrogen ions and these enzymes to escape into the cytoplasm of the cell, where they would do damage to the other cellular components.
Damage to a mitochondrion or chloroplast would affect energy production in the cell, but would not actively cause damage. Ribosomes don't have membranes.
The lysosomes contain an acidic environment and digestive enzymes. Damage to the membrane would allow hydrogen ions and these enzymes to escape into the cytoplasm of the cell, where they would do damage to the other cellular components.
Damage to a mitochondrion or chloroplast would affect energy production in the cell, but would not actively cause damage. Ribosomes don't have membranes.
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Among the most important pH buffer systems in humans is the bicarbonate buffer, which keeps the blood at a remarkably precise 7.42 pH. The bicarbonate buffer system uses a series of important compounds and enzymes to make the system function. Figure 1 depicts the key reactions that take place.

The activity of this buffer system is mainly controlled by the renal and respiratory systems. The renal system excretes bicarbonate in the urine, while the respiratory system “blows off” carbon dioxide as needed. By balancing these two systems as needed, blood pH is maintained in such a narrow range.
What is the predicted molecular orbital hybridization state of the carbon in carbonic acid?
Among the most important pH buffer systems in humans is the bicarbonate buffer, which keeps the blood at a remarkably precise 7.42 pH. The bicarbonate buffer system uses a series of important compounds and enzymes to make the system function. Figure 1 depicts the key reactions that take place.
The activity of this buffer system is mainly controlled by the renal and respiratory systems. The renal system excretes bicarbonate in the urine, while the respiratory system “blows off” carbon dioxide as needed. By balancing these two systems as needed, blood pH is maintained in such a narrow range.
What is the predicted molecular orbital hybridization state of the carbon in carbonic acid?
Carbons bound via one double bond are sp2 hybridized, as long as the remaining two bonds are each sigma bonds. Take the number of sigma bonds and subtract one for your exponent in the spx expression.
Carbons bound via one double bond are sp2 hybridized, as long as the remaining two bonds are each sigma bonds. Take the number of sigma bonds and subtract one for your exponent in the spx expression.
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Among the most important pH buffer systems in humans is the bicarbonate buffer, which keeps the blood at a remarkably precise 7.42 pH. The bicarbonate buffer system uses a series of important compounds and enzymes to make the system function. Figure 1 depicts the key reactions that take place.

The activity of this buffer system is mainly controlled by the renal and respiratory systems. The renal system excretes bicarbonate in the urine, while the respiratory system “blows off” carbon dioxide as needed. By balancing these two systems as needed, blood pH is maintained in such a narrow range.
The bond that is present between the carbon atom and the carbonyl oxygen atom in carbonc acid is best described as having which of the following?
Among the most important pH buffer systems in humans is the bicarbonate buffer, which keeps the blood at a remarkably precise 7.42 pH. The bicarbonate buffer system uses a series of important compounds and enzymes to make the system function. Figure 1 depicts the key reactions that take place.
The activity of this buffer system is mainly controlled by the renal and respiratory systems. The renal system excretes bicarbonate in the urine, while the respiratory system “blows off” carbon dioxide as needed. By balancing these two systems as needed, blood pH is maintained in such a narrow range.
The bond that is present between the carbon atom and the carbonyl oxygen atom in carbonc acid is best described as having which of the following?
The bond in question is a double bond, and thus is composed of one sigma and one pi bond.
The bond in question is a double bond, and thus is composed of one sigma and one pi bond.
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Under normal circumstances, which of the following carbons will be sp3 hybridized?
Under normal circumstances, which of the following carbons will be sp3 hybridized?
Carbanions are usually sp3 hybridized. Free radical carbons, carbocations, and double bonded carbons are all sp2 hybridized.
Carbanions are usually sp3 hybridized. Free radical carbons, carbocations, and double bonded carbons are all sp2 hybridized.
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When formic acid is completely reduced, methanol is formed.
What is the hybridization of the carbon in formic acid, compared to the carbon in methanol?
When formic acid is completely reduced, methanol is formed.
What is the hybridization of the carbon in formic acid, compared to the carbon in methanol?
In order to find the hybridization of an atom, simply count the number of sigma bonds and lone pair electrons around the atom. The carbon in formic acid is double bonded to an oxygen, and has two single bonds. This means that it has sp2 hybridization. Upon being reduced to methanol, the carbon now has four single bonds surrounding it. As a result, the carbon now has sp3 hybridization.
Remember that a triple bond corresponds to sp hydrization, a double bond to sp2, and single bonds to sp3 for a carbon atom.
In order to find the hybridization of an atom, simply count the number of sigma bonds and lone pair electrons around the atom. The carbon in formic acid is double bonded to an oxygen, and has two single bonds. This means that it has sp2 hybridization. Upon being reduced to methanol, the carbon now has four single bonds surrounding it. As a result, the carbon now has sp3 hybridization.
Remember that a triple bond corresponds to sp hydrization, a double bond to sp2, and single bonds to sp3 for a carbon atom.
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Which compound will have the highest bond energy?
Which compound will have the highest bond energy?
In organic chemistry, the trend is that bond length is inversely proportional to bond energy. Shorter bonds result in a higher bond energy. The double bond in ethene is the shortest bond out of all the others. As a result, it has the highest bond energy.
Note that in benzene there are three double bonds and three single bonds between carbons, however, resonance means that each of these only has partial double bond character, and is therefore longer than a pure double bond.
In organic chemistry, the trend is that bond length is inversely proportional to bond energy. Shorter bonds result in a higher bond energy. The double bond in ethene is the shortest bond out of all the others. As a result, it has the highest bond energy.
Note that in benzene there are three double bonds and three single bonds between carbons, however, resonance means that each of these only has partial double bond character, and is therefore longer than a pure double bond.
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The answer is arrows A and C. The carbon that is pointed to by arrow C is
hybridized. We see that its bond angles are at 120º (the full substituent points into the page) with a p-orbital that is involved in the pi bond of the carbonyl. Phenyl rings are also made up of carbons that are all
hybridized. The nitrogen pointed to by arrow B has two electrons that are not shown, but cause the atom to be
hybridized. The methyl groups denoted by arrow D are also
hybridized.
We can quickly tell the hybridization of atoms by observing their double bonds and unbonded electrons. As a rule of thumb, any carbon, nitrogen, or oxygen involved in a double bond will be
hybridized. Any of these atoms with no double bonds will be
hybridized. Finally, nitrogens or carbons involved in triple bonds are
hybridized.
The answer is arrows A and C. The carbon that is pointed to by arrow C is hybridized. We see that its bond angles are at 120º (the full substituent points into the page) with a p-orbital that is involved in the pi bond of the carbonyl. Phenyl rings are also made up of carbons that are all
hybridized. The nitrogen pointed to by arrow B has two electrons that are not shown, but cause the atom to be
hybridized. The methyl groups denoted by arrow D are also
hybridized.
We can quickly tell the hybridization of atoms by observing their double bonds and unbonded electrons. As a rule of thumb, any carbon, nitrogen, or oxygen involved in a double bond will be hybridized. Any of these atoms with no double bonds will be
hybridized. Finally, nitrogens or carbons involved in triple bonds are
hybridized.
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For a compound to be considered aromatic, it must be flat, cyclic, and conjugated and it must obey Huckel's rule. Huckel's rule states that an aromatic compound must have
pi electrons in the overlapping p orbitals in order to be aromatic (n in this formula represents any integer). Only compounds with 2, 6, 10, 14, . . . pi electrons can be considered aromatic. Compound A has 6 pi electrons, compound B has 4, and compound C has 8. This eliminates answers B and C. Answer D is not cyclic, and therefore cannot be aromatic. The only aromatic compound is answer choice A, which you should recognize as benzene.
For a compound to be considered aromatic, it must be flat, cyclic, and conjugated and it must obey Huckel's rule. Huckel's rule states that an aromatic compound must have pi electrons in the overlapping p orbitals in order to be aromatic (n in this formula represents any integer). Only compounds with 2, 6, 10, 14, . . . pi electrons can be considered aromatic. Compound A has 6 pi electrons, compound B has 4, and compound C has 8. This eliminates answers B and C. Answer D is not cyclic, and therefore cannot be aromatic. The only aromatic compound is answer choice A, which you should recognize as benzene.
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One component of the immune system is the neutrophil, a professional phagocyte that consumes invading cells. The neutrophil is ferried to the site of infection via the blood as pre-neutrophils, or monocytes, ready to differentiate as needed to defend their host.
In order to leave the blood and migrate to the tissues, where infection is active, the monocyte undergoes a process called diapedesis. Diapedesis is a process of extravasation, where the monocyte leaves the circulation by moving in between endothelial cells, enters the tissue, and matures into a neutrophil.
Diapedesis is mediated by a class of proteins called selectins, present on the monocyte membrane and the endothelium. These selectins interact, attract the monocyte to the endothelium, and allow the monocytes to roll along the endothelium until they are able to complete diapedesis by leaving the vasculature and entering the tissues.
The image below shows monocytes moving in the blood vessel, "rolling" along the vessel wall, and eventually leaving the vessel to migrate to the site of infection.

Neutrophils make use of radical species to digest phagocytosed material. Which of the following is true of radical reactions?
One component of the immune system is the neutrophil, a professional phagocyte that consumes invading cells. The neutrophil is ferried to the site of infection via the blood as pre-neutrophils, or monocytes, ready to differentiate as needed to defend their host.
In order to leave the blood and migrate to the tissues, where infection is active, the monocyte undergoes a process called diapedesis. Diapedesis is a process of extravasation, where the monocyte leaves the circulation by moving in between endothelial cells, enters the tissue, and matures into a neutrophil.
Diapedesis is mediated by a class of proteins called selectins, present on the monocyte membrane and the endothelium. These selectins interact, attract the monocyte to the endothelium, and allow the monocytes to roll along the endothelium until they are able to complete diapedesis by leaving the vasculature and entering the tissues.
The image below shows monocytes moving in the blood vessel, "rolling" along the vessel wall, and eventually leaving the vessel to migrate to the site of infection.
Neutrophils make use of radical species to digest phagocytosed material. Which of the following is true of radical reactions?
Radical reactions have an sp2, trigonal planer carbon radical intermediate. Carbon radicals are most stable as tertiary species.
Radical reactions have an sp2, trigonal planer carbon radical intermediate. Carbon radicals are most stable as tertiary species.
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2-butyne contains all of the following types of bonds except .
2-butyne contains all of the following types of bonds except .
2-butyne has the following chemical structure.

The end carbons have
hybridization (form single bonds only), while the middle two carbons have
hybridization (involved in a triple bond). There are no
hybridized carbons in this molecule.
2-butyne has the following chemical structure.
The end carbons have hybridization (form single bonds only), while the middle two carbons have
hybridization (involved in a triple bond). There are no
hybridized carbons in this molecule.
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The degree of unsaturation for ephedrine (shown below) is .

The degree of unsaturation for ephedrine (shown below) is .
The degree of unsaturation is equal to the number of rings plus the number of pi bonds in a molecule. Ephedrine has one ring and three pi bonds, so its degree of unsaturation is four.
To arrive at this answer, one could also use the formula below, where
is the number of carbon atoms,
is the number of hydrogen atoms,
is the number of halogen atoms, and
is the number of nitrogen atoms.

For ephedrine,
,
,
, and
.

The degree of unsaturation is equal to the number of rings plus the number of pi bonds in a molecule. Ephedrine has one ring and three pi bonds, so its degree of unsaturation is four.
To arrive at this answer, one could also use the formula below, where is the number of carbon atoms,
is the number of hydrogen atoms,
is the number of halogen atoms, and
is the number of nitrogen atoms.
For ephedrine, ,
,
, and
.
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The compound below is reacted with
. What is the final hybridization around the initially chiral center carbon when the reaction is complete?

The compound below is reacted with . What is the final hybridization around the initially chiral center carbon when the reaction is complete?
The initially chiral carbon has an
hybridization. Once treated with
,an oxidizing agent, the secondary alcohol in the compound is oxidized to a ketone. The central carbon is no longer a chiral center (a carbon with a double bond cannot be chiral), and the double bond (pi-bond) formed between carbon and oxygen gives the molecule an
hybridization.
hybridization is formed with triple bonds, and an
hybridization does not exist.
The initially chiral carbon has an hybridization. Once treated with
,an oxidizing agent, the secondary alcohol in the compound is oxidized to a ketone. The central carbon is no longer a chiral center (a carbon with a double bond cannot be chiral), and the double bond (pi-bond) formed between carbon and oxygen gives the molecule an
hybridization.
hybridization is formed with triple bonds, and an
hybridization does not exist.
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