FLE 4
Paradoxical sleep occurs when electroencephalography (EEG) signals: A) during a sleep period become similar to those of a person who is awake. B) stop completely for a period of 20 minutes or more. C) during a sleep period vary randomly in both amplituide and duration. D) exhibit both sleep spindles and K-complexes.
Answer A is correct, rapid eye movement (REM) sleep, also called paradoxical sleep, is a period of sleep during which the skeletal muscles demonstrate apparent paralysis even though respiration rate increases and the brain's activity is similar to that of a person in an awake state. Answer B is false because a complete lack of EEG signals would indicate zero neurological activity, which would most likely only occur following brain death. Answer C is false because brain waves show characteristic patterns during REM sleep, not randomization. Answer D is false because sleep spindles and K-complexes are characteristic brain wave patterns observed during Stage 2 of the sleep cycle.
Suppose a novel protein is discovered that is easily incorporated into micelles. This protein is most likely: A) an integral membrane protein. B) a peripheral membrane protein. C) a beta-barrel protein. D) a structural protein.
Answer A is correct. Micelles are spheres of amphipathic molecules, usually lipids, with hydrophilic heads on the surface of the sphere and hydrophobic tails pointed into the center of the sphere. Because of this, a protein that can integrate into a micelle must also be amphipathic, featuring both polar and non-polar regions. Among the answer options given, only an integral membrane protein is definitely both hydrophobic and hydrophilic. A membrane protein will have a hydrophobic region that is embedded within the lipid bilayer and a hydrophilic region that interacts with either the cytosol or the extracellular, aqueous environment. Answer B is incorrect because while it is possible that a peripheral membrane protein has hydrophobic and hydrophilic regions, most peripheral membrane proteins interact solely with the polar head groups of the membrane, or with the polar regions of other integral proteins, and as such their surface regions are hydrophilic. Answer C is incorrect because again, there is no reason to assume that the beta barrel has hydrophobic regions. Many integral membrane proteins are beta barrels, because their unique structure makes them excellent membrane channels (the amino acids pointing out of the barrel can be hydrophobic, interacting with the membrane, and the amino acids pointing inward can be hydrophilic, aiding charged molecules or proteins to travel through the membrane). But not all beta barrels are amphipathic, so choice C is not as strong of an answer as option A. Answer D is incorrect because, while many structural proteins are polar, not all of them are. Actin, keratin, and collagen are all examples of structural proteins, and none of them have structures that would make them suitable for integration into a micelle.
When the muscles of the diaphragm contract, the volume of the lungs is: A) increased, and the pressure inside the lungs is decreased. B) increased, and the pressure inside the lungs is increased. C) decreased, and the pressure inside the lungs is increased. D) decreased, and the pressure inside the lungs is decreased.
Answer A is correct. The Ideal Gas Law relates volume and pressure, showing that PV = constant. Therefore, pressure and volume are inversely proportional. Further, the contraction of the diaphragm muscle changes the shape of the muscle from concave-up to approximately flat. This increases the volume of the lungs, decreasing the pressure inside the lungs according to this inverse relationship. Air then diffuses into the lungs down its pressure gradient until the pressure inside the lungs is equal to atmospheric pressure. These facts are represented by answer choice A. Answer B incorrectly predicts that the pressure inside the lungs increases. Answer C is incorrect for inhalation (contraction of the diaphragm), but would be true for exhalation. Answer D incorrectly predicts both the volume change and the relationship between pressure and volume.
In the human auditory system, which cell type is responsible for transduction of an auditory signal? A) Inner hair cells of the cochlea B) Outer hair cells of the cochlea C) Hair cells of the semicircular canals D) Cranial nerve cells with synapses in the inner ear
Answer A is correct. The inner hair cells of the cochlea are the sensory receptors for the human auditory system. Answer B is false because the outer hair cells of the cochlea are used for mechanical amplification. Answer C is false because the hair cells of the semicircular canals transduce vestibular information regarding balance and orientation. Answer D is false because cranial nerve endings do not receive auditory signals directly from the inner ear. The auditory branch of the vestibulocochlear nerve synapses with the inner hair cells.
Major Histocompatibility Complex II (MHC-II) proteins are cell surface proteins that function in the immune system to accomplish antigen presentation. Following translation, which organelle is responsible for trafficking these proteins to the cell surface? A) Vesicles B) Mitochondria C) Ribosomes D) Lysosomes
Answer A is the correct choice. Vesicles traffic proteins to be expressed on the surface of the plasma membrane. Following translation by a ribosome at the rough ER, the protein may undergo posttranslational modification, then it will be processed by the Golgi and budded off into a vesicle targeted for the membrane. The vesicle will then fuse with the plasma membrane so that the proteins on the inside of the vesicle membrane become the proteins on the outer leaflet of the plasma membrane. Mitochondria function in respiration and have no role in intracellular transport, eliminating Answer B. Ribosomes function in translation, but not protein trafficking, so Answer C is eliminated. Lysosomes contain hydrolytic enzymes that would destroy the MHC molecules if they were ever inside of a lysosome, eliminating Answer D.
The researchers used participant observation as their primary means of data collection. This suggests that the researchers most likely: A) observed the social phenomena being studied from a distance. B) took part in the social phenomena being studied. C) observed the social phenomena being studied from behind two-way glass. D) randomly separated subjects into two observation groups.
Answer B is correct. Basic knowledge of the differences between social science research methods is needed to successfully answer this question. Participant observation requires the researcher to directly participate in the social phenomena being studied, making Answer B correct. Answer A is incorrect because this does not include the fact that the researcher was immersed in the social situation being studied, which is the hallmark of the participant observation methodology. Answer C is incorrect because this would be nearly the opposite of taking part in the social phenomenon with the subjects. Answer D is incorrect because random assignment is a characteristic of the experimental research method, not participant observation.
A woman involved in a violent riot explains to the police that the vandalism in which she participated was a complete departure from her normal pattern of behavior. Such a change in behavior while participating in a large group activity could be the result of which phenomenon? A) Group think B) Deindividuation C) Social obedience D) Heuristic decision making
Answer B is the correct choice. Deindividuation occurs when people in a group cease to act as individuals with an individual sense of responsibility. Rather, they take on a mob mentality dictated by the group. Answer A is incorrect because group think is a different phenomenon whereby individuals value group cohesion over individual responsibility. This causes individuals to adopt the views of the rest of group even when contrary to their own views. Answer C, social obedience, occurs when individuals obey orders which may be contrary to their own values. While it is possible that a group leader could have ordered the woman to participate, this cannot be assumed when nothing in the stem suggests this specific circumstance. Answer D, heuristic decision making, is a cognitive shortcut individuals use when making decisions. This concept is not directly related to the scenario described in the stem.
A new bacteria is discovered that utilizes a novel nucleotide, designated as H. The H nucleotide replaces guanine in the bacteria's genome and base pairs with cytosine. This bacteria is likely to be highly successful at evading host immune system responses because the: A) bacteria's genome will not be recognized by antibodies in the host's immune system. B) bacteria will produce new proteins which cannot be detected by the host's immune system. C) H nucleotide will disrupt restriction endonucleases that target non-self DNA molecules to degrade them. D) H nucleotide will make the bacterial surface proteins more similar to human surface proteins.
Answer C is correct. The newly discovered bacterium has a genome that uses ATCH instead of ATCG, but no other changes are described. We are told that H base pairs with C, so one can assume that it behaves in most respects just like G does. Answer C is the best answer because one way that organisms fight foreign invaders is through restriction endonucleases that recognize 'non-self" DNA sequences. These endonucleases have very specific restriction sites (It would be very dangerous to have endonucleases without specific sites, since they could cleave any DNA). Answer A is incorrect because antibodies are generated against proteins, not DNA molecules. Answer B is incorrect because there is nothing to indicate that new proteins are being generated. If H base pairs with C, tRNA should interact with codons the same way whether H or G is being used. Answer D is incorrect for the same reason, there is no reason to believe the bacteria will produce new proteins, or that those proteins will be more like host surface proteins because of the H for G transition.
Suppose a molecule composed of atoms A and B features a permanent dipole. This dipole is mostly likely the result of: A) an odd number of neutrons in the central atom. B) an incomplete octet for either atom, or both atoms. C) the presence of pi bonds between atoms A and B. D) the uneven distribution of electrons between atoms A and B.
Answer D is correct. A polar molecule has a positive pole and a negative pole, resulting from the uneven distribution of electrons. The negative pole has a surplus of electrons, while the positive pole has a deficiency of electrons. Choice A is incorrect because neutrons do not affect the polarity of a molecule. Choice B is incorrect; an incomplete octet does not necessarily indicate a permanent dipole. BF3 is an example of a nonpolar molecule with a central atom that has an incomplete octet. Choice C is incorrect because pi bonds can be present in both polar molecules (CO for example) and nonpolar molecules (C2H4 for example).
If 1.0 mL of 1.0 M NaNO3 is added to 100.0 mL of 0.001 M HNO3 what change in pH is expected? A) No pH change B) Very large decrease C) Moderate decrease D) Very small increase
Answer D is correct. NO3- is the conjugate base of a strong acid, so adding NaNO3 does not affect pH other than by diluting the solution. By adding just 1.0 mL of the NaNO3 to 100 mL, the solution is diluted by about 1 %. Since pH = -log[H+], the final [H+] would be slightly lower and pH would be slightly higher, making Choice D correct. Choice A is incorrect; the change in pH would be very small. Choices B and C are both wrong because the pH will increase slightly, it will not decrease.
Under normal physiological conditions, DSBs in DNA are repaired by which mechanism? A) Nucleotide-excision repair B) Base-excision repair C) Mismatch repair D) Homologous recombination
Answer D is correct; all the other repair mechanisms listed are for single-stranded DNA. Answer D is the only repair mechanism for double-stranded DNA. Answers A and C are both mechanisms wherein a small region of a single strand of the DNA is removed and replaced. Answer B is a mechanism where a single base is removed and replaced.
The VC of a patient suffering from asthma was determined using the spirometer shown in Figure 1. If a volume of 0.43 L was recorded by the technician at 25 °C and 750 torr, how many moles of air were exhaled by the patient? A) 9.66 x 102 mol B) 1.68 x 10-1 mol C) 3.36 x 10-2 mol D) 1.68 x 10-2 mol
Answer choice D is correct. This question requires the calculation of the number of moles of a gas using the Ideal Gas Law: PV = nRT. In addition, the vapor pressure of water must be subtracted because the gas is collected over water. Therefore, the pressure of the gas = total pressure - water vapor pressure = 750 torr - 24 torr = 726 torr. The pressure of the gas must be converted to atm = 726 torr × (1 atm/760 torr) » 0.95 atm. The number of moles can then be calculated using n = PV/RT = (0.95 atm × 0.43 L)/(0.0821 L·atm·mol-1·K-1 × 298 K). Rounding and converting to scientific notation gives: n = (1 atm x 0.4 L)/(8 x 10-2 L·atm·mol-1·K-1 × 3 x 102 K) = (4 x 10-1)/(2.4 x 101) = 1.66 x 10-2 mol. This is very close to Answer D. Answers A, B and C all result from various calculation errors. Answer A could also be dismissed based on intuition because it is an enormously large number of moles for the relatively small volume of air that could be expelled by human lungs. It is worth noting that after we rounded to perform the calculation, the original step of subtracting vapor pressure was essentially negated. However, we have included this step because it is an important concept that must be recognized for any situation where gas pressure is being measured over a volatile liquid. In another MCAT question, the difference between considering vapor pressure and failing to do so could easily be the difference between the correct answer and one of the distractors.
Match the following with the correct theory of either psychoanalytical, social learning theory, behaviorism: B) People are motivated to repeat behaviors that are positively reinforced. C) Individuals are primarily motivated by unresolved childhood conflicts. D) Individuals achieve self-actualization by mirroring behaviors observed in others.
B- behaviorism C-psychoanalytical D- social learning theory
Which of the following represents the correct order in which visual cues would have been transmitted from a participant's eye to his or her brain? A) Photoreceptor, optic nerve, lateral geniculate nucleus, striate cortex B) Photoreceptor, optic nerve, medial geniculate nucleus, striate cortex C) Retinal ganglion cell, photoreceptor, optic nerve, striate cortex D) Retinal ganglion cell, optic nerve, inferior colliculus, striate cortex
Choice A is correct. Light activates photoreceptors in the retina, which subsequently transmit information through the optic nerve. The lateral geniculate nucleus of the thalamus receives visual input from the retina and then sends that information on to the primary visual cortex, also known as the striate cortex. This correct order of processing is only reflected by answer choice A. Answer B is incorrect because the medial geniculate nucleus of the thalamus is involved in processing auditory information. Answer C is incorrect because the retinal ganglion cells receive information from photoreceptors, rather than the reverse. Although retinal ganglion cells would actually be involved in the correct pathway described in Answer A, the ordering is correct; while in Answer C the order is incorrect. Light signals cannot be processed first by the ganglion and then by a photoreceptor. Answer D is incorrect because the inferior colliculus is a midbrain structure involved in auditory processing, not visual processing. Note: In terms of correct order of processing, "retinal ganglion cell" would be inserted in Answer A between "photoreceptor" and "optic nerve."
The IC3 stores a small amount of energy by charging an integrated capacitor using direct current from the transducer. If the transducer produces a voltage, V, and the capacitor has a capacitance of C, which expression gives the charge stored on the capacitor? A) CV B0 C/V C) V/C D) ½ CV2
Choice A is correct. This problem requires an understanding of the relationship between charge, voltage, and capacitance. Capacitance can be thought of as the amount of charge stored per volt: C = Q/V. Solving for charge gives the equation: Q = CV. This matches answer choice A. Choices B and C are incorrect because neither relation will give the magnitude of the charge stored on the capacitor. Choice D could be a tempting distractor because it is a correct expression for something else, the potential energy stored by a capacitor
One of the bone-resorbing enzymes secreted by osteoclasts requires a covalently bound zinc ion to exhibit normal enzyme function. In this scenario, zinc is acting as: I. a coenzyme. II. an allosteric effector. III. a prosthetic group. A) III only B) I and II only C) I and III only D) I, II, and III
Choice A is the best answer. Because the question states that the zinc is covalently bound and is necessary for normal function, the zinc is an example of a prosthetic group; which is a non-protein cofactor that is tightly bound to an enzyme and is necessary for its function. This eliminates Answer B because it does not include Statement III, Coenzymes are organic molecules that are required by an enzyme to function, but are not usually covalently bound. They are differentiated from prosthetic groups because they are loosely bound to the enzyme, whereas prosthetic groups are tightly bound (usually, but not universally, via a covalent bond). While coenzymes are always organic non-protein molecules, prosthetic groups can be either organic or inorganic. Because zinc is covalently bound to the enzyme, it is not "loosely" bound and therefore cannot be classified as a coenzyme. This makes Statement I false and eliminates answers B, C and D because they all include Statement I. Allosteric effectors are molecules that bind to an enzyme at a site other than the enzyme's active site and regulate its function. Because allosteric effectors either upregulate or downregulate enzyme function, the zinc mentioned in the stem cannot be an allosteric regulator. According to the stem, the enzyme cannot function normally without the zinc, whereas enzymes can and do function without allosteric modulators, they just function differently under that regulation (e.g., increased or decreased reaction rate, binding affinity, etc.). This makes Statement II false, eliminating answers B and D. Only Statement III is true, so choice A is the best answer.
Which hypothetical finding provides the most support for the psychological theories espoused by Abraham Maslow? A) People with unresolved deficiency needs do not focus on self-actualization. B) People are motivated to repeat behaviors that are positively reinforced. C) Individuals are primarily motivated by unresolved childhood conflicts. D) Individuals achieve self-actualization by mirroring behaviors observed in others.
Choice A is the correct answer. Abraham Maslow is the creator of Maslow's hierarchy of needs. Maslow stated that the lower, or fundamental needs in this pyramid were "deficiency" or "d-needs." If these fundamental needs are not satisfied, a person is not motivated to work toward higher-order needs. Answer B is incorrect because this finding would support the theory of behaviorism, or more specifically, operant conditioning. Answer C is false because this finding would support the ideas suggested by psychoanalytic theorists such as Freud. Answer D is false because this finding would support social learning theory.
A person suffering from insomnia would receive the greatest short-term benefit from which type of therapy? A) Cognitive-behavioral therapy B) Group therapy C) Electroconvulsive therapy D) Aversion therapy
Choice A is the correct answer. Cognitive-behavioral therapy would be the most beneficial to someone who is suffering from insomnia, as this form of therapy is a short-term therapy that focuses on helping clients deal with a specific problem, such as insomnia, smoking cessation, or weight loss. During this form of therapy, clients learn how to identify and change patterns that negatively influence behavior. Answer A is incorrect because group therapy would not be particularly beneficial to someone suffering from insomnia. Group therapy is focused primarily on group dynamics such as support, interpersonal relationships, and group cohesion. Answer C is incorrect because electroconvulsive therapy is a procedure, performed under general anesthesia, in which small electric currents are passed through the brain, intentionally triggering a brief seizure. This treatment is rarely employed, and only after other therapeutic options have been exhausted. Answer D, aversion therapy, is a form of behavior therapy in which an aversive (causing a strong feeling of dislike or disgust) stimulus is paired with an undesirable behavior in order to reduce or eliminate that behavior. This form of therapy might be used to assist with something like alcohol or drug addiction, or to eliminate an undesirable habit such as nail biting, but could not be used to treat insomnia. The desired remedy is increased sleep and attempting to pair "awakeness" with an aversive stimulus to reinforce sleep would be extremely problematic.
Figure 1 suggests participants have more conservative attitudes when asked whether race inequality is due to structural factors, but have more liberal attitudes when asked if whites have the right to live in segregated neighborhoods. Which sociological concept best explains this trend? A) Symbolic racism B) Jim crow racism C) Prejudice theory D) Social control theory
Choice A is the correct answer. Figure 1 suggests that respondent attitudes about race are mixed. They do not support overtly racist practices such as segregation, but still believe that racism is not a structural or institutional issue in the United States. Many race scholars call this "symbolic racism," in which respondents believe that racism is wrong but do not see racism as a significant institutional problem in society since the 1960s. Answer B is wrong because this phrase is used to explain institutional racism, which is not what the respondents suggested in both responses. Answer C is wrong because this question does not ask about levels of prejudice and this theory suggests that people are prejudice due to outgroup competition. Answer D is wrong because social control theory does not apply to discussions about racism but rather to the processes of learning, particularly about social deviance and crime.A is correct. The data in Figure 1 shows that for angry expressions of emotion, females recognized anger in male actors better than their male counterparts, however there was no difference for female actors nor was there any difference between males and females for female actors.
Many viruses that invade human hosts have developed the ability to inhibit normal cellular transcription by expressing inhibitor molecules that act in the: A) nucleoplasm. B) mitochondria. C) cytoplasm. D) endoplasmic reticulum.
Choice A is the correct answer. Transcription occurs in the nucleoplasm of the nucleus. RNA polymerase uses the DNA template of the chromosomes to produce a pre-mRNA. The pre-mRNA is then processed to mRNA and moves to the cytoplasm for translation. Translation, not transcription, occurs in the cytoplasm, which eliminates Answer C. Translation of mRNA that encodes proteins for export is often associated with the rough endoplasmic reticulum, but this is translation, not transcription, which eliminates Answer D. Mitochondrial transcription and translation are labeled as "mitochondrial" to distinguish them from cellular process, eliminating Answer B.
I. CO2 (aq) + H2O (l) ⇄ H2CO3 (aq) II. H2CO3 (aq) + H2O (l) ⇌ H3O+ + HCO3- (aq) III. CO2 (aq) ⇌ CO2 (g) The enzyme carbonic anhydrase is named after which reaction from Figure 1? A) Reaction I B) The reverse of Reaction I C)Reaction II D) The reverse of Reaction II
Choice B is correct. With the exception of a few enzymes with common historical names, enzymes are usually named after the reaction they catalyze. In fact, this protocol is of such importance that it is included specifically on the AAMC's MCAT-2015 topics list (Enzymes: Classification by Reaction Type). The term "anhydrase" implies the removal of water, and only the reverse of Reaction I involves the removal of a water molecule from a compound. Although carbonic anhydrase is named after the reverse of this reaction, remember that enzymes catalyze reactions in BOTH directions. Choice A is incorrect because Reaction I is an example of hydration; adding a water molecule to CO2. Answer C is incorrect because Reaction II includes water as a reactant, not a product. Answer D is incorrect because although water is formed as a product of the reversal of Reaction II, an anhydrase enzyme removes water from a single substrate. It may also be helpful to recall the passage statement that "Carbonic anhydrase catalyzes the aqueous equilibrium between carbonic acid, water and carbon dioxide." This points directly to Reaction I, while the removal of a water molecule dictates the reversal of Reaction I.
Which physiological mechanism is LEAST likely to result in a significant decrease in blood acidity? A) Exhalation of carbon dioxide B) Release of H3PO4 into the blood stream C)Conversion of carbon dioxide into bicarbonate in the blood D)Excretion of protons into the urine by the kidneys
Choice B is the best answer. The major physiological mechanisms used to control blood pH include exhalation of carbon dioxide, conversion of carbon dioxide into bicarbonate in the blood, and the excretion of protons through the kidneys. In the precise way they are stated here, all three mechanisms will decrease blood acidity (i.e., increase blood pH). Answers A and C will decrease blood acidity according to Le Chatelier's Principle as it is applied to the following equation: CO2 + H2O ⇄ H2CO3 ⇄ H+ + HCO3- Answer D will decrease blood acidity by directly removing H+ ions from the blood. Answer B is the correct answer to this "LEAST" question type because the release of phosphoric acid into the blood would directly increase blood acidity, rather than decreasing it. However, this could be tempting to exclude if the student recalls that the phosphate buffer system plays a minor role in maintaining blood pH. However, this buffer is represented by the equation given below, and adding phosphoric acid to the blood would still increase blood acidity. Phosphoric acid will not only dissociate into dihydrogen phosphate and a hydrogen ion, but the resulting dihydrogen phosphate will result in the formation of additional protons according to Le Chatelier's Principle: H2PO4- ⇄ HPO42- + H+
Inactive osteoclasts feature smooth cell membranes, while activated osteoclasts feature a ruffled cell membrane with numerous invaginations. What is the most plausible purpose for this change in cell membrane morphology? A) To increase cytoplasmic volume B) To increase cell membrane surface area C) To decrease absorption of bone minerals through the cell membrane D) To increase secretion of bone minerals necessary for bone formation
Choice B is the correct answer. Generally, when membranes of any kind are ruffled or invaginated, this results in an increase in cell membrane surface area. In fact, the membrane cannot attain a ruffled morphology without an increase in the lipid content of the membrane. Other examples of this trend can be seen in the inner mitochondrial membrane and the villi of the intestinal lining. In all these cases, the invaginations increase the surface area of an enclosed space (either a cell or an organ) to increase the area available for interaction with the extracellular environment. For osteoclasts, the increased surface area gives the cell more area with which to contact bone structure, secrete bone dissolving agents, and absorb the dissolved bone minerals. Answer A is incorrect because invaginations will not substantially change the volume of the cell. The membrane itself might become much longer, but because of the wavy nature of the membrane, the actual volume of the cell will remain about the same. Choice C is incorrect because increased surface area would not decrease absorption, it would increase it. Further, active osteoclasts are associated with increased bone resorption, not decreased bone resorption. D is incorrect because osteoclasts degrade and absorb bone material, they do not secrete minerals used for bone formation (that is the role of osteoblasts).
Which relative level of enzyme activity is required on the leading and lagging strands during DNA replication? A) Ligase is more active on the leading strand. B) Ligase is more active on the lagging strand. C) Helicase is more active on the leading strand. D) Helicase is more active on the lagging strand.
Choice B is the correct answer. Ligase seals the nicks after the RNA primers are removed and repaired by DNA polymerase. There is only one RNA primer on the leading strand, but many on the lagging strand as the result of Okasaki fragments. Therefore, ligase would be used more often on the lagging strand, which eliminates answer A. Helicase unwinds the double-stranded DNA to produce both the leading and lagging strand templates, so helicase does not favor one strand or the other strand, which eliminates answers C and D
Complete β-oxidation of the arachidic acid molecule shown will produce how many acetyl-CoA and succinyl-CoA molecules, respectively? (has 20 carbons) A) 19 and 1 B) 10 and 0 C) 8 and 1 D) 4 and 4
Choice B is the correct answer. The fatty acid shown is an even-numbered chain with 20 carbons. Therefore, it will be oxidized to form 10 acetyl CoA molecules and no succinyl CoA molecules. For each round of β-oxidation, an acetyl CoA is generated and the fatty acid is shortened by two carbons. The final round generates two acetyl CoA's. To calculate how many acetyl CoA's will be generated, simply divide the number of carbons by two. If the fatty acid shown had been an odd-numbered chain, the final step would involve cleaving a 5-carbon chain into an acetyl CoA (2 carbons) and a succinyl CoA (3 carbons). Answer A is incorrect because there are not enough carbons in the structure to support 19 acetyl CoA molecules, and also a succinyl CoA (that would require a fatty acid with 41 carbons). Answer C is incorrect because this would require a 19-carbon fatty acid, not a 20-carbon fatty acid. Answer D is incorrect because, to achieve these numbers, β-oxidation would have to cleave every 5 carbons into one acetyl CoA and one succinyl CoA. Succinyl CoA is only produced during the final step for odd-numbered fatty acid chains.
The diagram below depicts a transcription factor containing a zinc finger DNA-binding domain and an SH2 protein-protein interaction domain. If the transcription factor is necessary for expression of a recessive trait, which mutation would be most likely to result in the loss of the recessive phenotype in a homozygous recessive offspring? A) Silent point mutation in the SH2 domain B) Nonsense mutation near the amino terminus C) Frameshift mutation at the carboxy terminus D) Three-base insertion mutation near the amino terminus
Choice B is the correct answer. Translation proceeds from the 5' to the 3' end, such that the amino terminus end of the protein is translated first. Therefore, mutations at the amino terminus will have the potential to affect the rest of the protein sequence and thus eliminate the effect of the transcription factor. A silent mutation does not change amino acid sequence, so answer A is incorrect. A nonsense mutation at the amino terminus, however, would introduce a stop codon that would prevent translation of the rest of the protein. The mutation in answer B would therefore eliminate the production of the phenoytpe. By contrast, a frameshift mutation at the carboxyl terminus would probably have an effect on all subsequent codons, but the SH2 and zing finger domains would remain intact. A three-base insertion near the amino terminus could introduce an extra amino acid in the protein sequence and shift all subsequent amino acids toward the carboxyl terminus, but because the reading frame would be unaltered, the activity of the SH2 and zinc finger domains would remain intact. Answer B is therefore correct and answers C and D are incorrect.
I. CO2 (aq) + H2O (l) ⇄ H2CO3 (aq) II. H2CO3 (aq) + H2O (l) ⇌ H3O+ + HCO3- (aq) III. CO2 (aq) ⇌ CO2 (g) Which of the following is a logical finding from a subsequent study involving blood homeostasis? A) Carbonic anhydrase violates Le Chatelier's Principle. B) CO2 gas is nearly insoluble in human blood at physiological pH. C) Reaction II resists dramatic pH shifts in solutions titrated with acid. D)Ambient air PCO2 is greater than alveolar PCO2.
Choice C is correct. Although this fact was not discussed in the passage, Reaction II is the buffer responsible for maintaining blood pH, a concept that is widely taught in undergraduate chemistry courses. Choice A should be ruled out because Le Chatelier's Principle holds for all chemical equilibriums. Choice B is a clearly false relationship; CO2 must be soluble to some degree in blood or it could not be transported by the blood. Therefore, this is a highly unlikely, if not impossible, hypothetical finding from a subsequent study. Choice D is also a false statement; alveolar PCO2 must be greater than ambient PCO2 because CO2 diffuses from the blood into the alveoli at the lungs.
Calcium is a necessary structural or functional component in which of the following processes? I. Bone tissue formation II. Blood clotting III. Muscle contraction IV. Nerve signal transmission A) I and IV only B) III and IV only C) I, III, and IV only D) I,II, III, and IV
Choice C is correct. Calcium combines with phosphate and hydroxide in hydroxyapatite, the major component of the extracellular bone matrix. This makes Statement I true and allows the student to reject Answer B because it does not include Statement I. Calcium is not required in blood clotting, so Statement II is false, and therefore Answer D can be eliminated. As described in the passage, calcium is required for muscle contraction. Thus, Statement III is true and Answer A can be eliminated. However, please note that the role of calcium in both smooth and skeletal muscle contraction is required background knowledge for the MCAT. In other words, this would be a fair question even if the passage had not explained the role of calcium in smooth muscle contraction. Finally, calcium in necessary for the release of neurotransmitter bundles at the synapse, so Statement IV is also true. This makes Answer C correct, because statements I, III and IV are all true.
Suppose it is discovered that women are more likely to respond positively to inventory questions that ask about episodes of "crying," "self-dislike," or "body image preoccupation." Such a finding may be an example of: A) stereotype threat. B) implicit bias. C) measurement bias. D) depressive realism.
Choice C is correct. If a depression inventory captures behaviors or feelings that women in general are more likely to report, or more willing to endorse, regardless of their actual level of depression, then this represents a potential measurement bias in the inventory itself. The inventory would be measuring behaviors and feelings that are related to being female, rather than symptoms related directly to depression. This supports Answer C. Answer A, stereotype threat, refers to being at risk of confirming, by one's own performance or behavior, a negative stereotype about one's own stereotyped group. This is not relevant to the self report of depressive symptoms, so Answer A should be dismissed. Answer B, implicit bias, refers to attitudes or stereotypes that affect our understanding, actions, and decisions in an unconscious manner. This is also unrelated to self-reports of depression symptoms. Answer D, depressive realism, refers to the hypothesis that depressed individuals make more realistic inferences than do non-depressed individuals. This is also unrelated to self reports of depressive symptoms, so Answer D cannot be correct.
Which macromolecule is capable of acting in vivo as a structural component, a catalyst, and a mediator of cell communication? A) Nucleic acids B) Phospholipids C) Proteins D) Lipids
Choice C is correct. Proteins are frequently discussed in biochemistry as enzymes, but they also have many non-enzymatic functions, including acting as structural components, components in plasma membranes, cell signaling molecules, antibodies, and so forth. Answer A is not correct because nucleic acids usually contain the information to make proteins, but cannot participate in all of the functions listed. Choice B is not correct because phospholipids are structural parts of the plasma membrane but they do not act as enzymes. Choice D is not correct because lipids do not act as enzymes.
Sound levels are measured in decibels according to the equation below, where I0 is the nominal threshold of human hearing, 10-12 W/m2.A sound source located 1.0 m from a microphone is measured at 80 dB. The same sound measured at a distance of 3.0 m from the microphone will have a decibel rating of: β = 10log10(I/I0) A) 50 dB B) 60 dB C) 70 dB D) 77dB
Choice C is the correct answer. This problem requires understanding two important principles. The first principle is that typically sound waves spread out in all directions according to an inverse square law. One can see this by noting that if there is no loss of energy due to absorption/attenuation, the energy passing through the area of any imaginary sphere surrounding the source must be the same. Since the sphere area grows with the radius squared, the sound level must drop as the inverse of radius squared. The same would apply to light intensity from a light bulb. Therefore, doubling the distance from the source causes the intensity to go down by a factor of 4. Or, in this case, tripling the distance causes the intensity to go down by a factor of 9. The second principle one must understand is how the logarithmic decibel scale works: multiplying the intensity by 10 causes a +10 change to the decibel number. For example, 90 dB is 10 times more intense than 80 dB, and 110 dB is 1000 times more intense than 80 dB. In this problem, the intensity goes down by a factor of 9, which is close to 10, so the decibel number should have 10 subtracted from it. Thus 70 dB is the correct answer (Answer C). Choices A or D (reducing the decibels by 30 or by 3, respectively) might be tempting if you don't know how tripling distance actually affects the decrease in intensity. Choice B is similarly incorrect as the number must be close to a 10 dB decrease.
In what way does smooth muscle contraction differ from skeletal muscle contraction? A) Only smooth muscle contraction involves the formation of myosin cross bridges. B) Only smooth muscle contraction utilizes troponin and transverse tubules. C) For skeletal muscle contraction only, troponin is necessary to expose the actin binding site. D) For skeletal muscle contraction only, calcium is necessary to initiate contraction.
Choice C is the correct answer. Troponin is required for skeletal muscle contraction, but is not involved in smooth muscle contraction. Answer A is not correct because skeletal muscle cells do utilize cross bridges. Choice B is not correct because it is skeletal muscle contraction which utilizes troponin and T-tubules, not smooth muscle contraction. Choice D is not correct because calcium is required for contraction in both smooth and skeletal muscle.
A mother is frustrated with her son who refuses to complete his math homework. A behaviorist would suggest which intervention to increase the amount of time the son spends doing his math homework? A) Promise the child a "math-free" weekend to reduce homework-related stress. B) Give the child additional chores as a punishment for poor math scores. C) Promise the child a monetary reward if he earns a high grade in his math class. D) Give the child small gifts each time he studies his math homework.
Choice D is correct. Based on behaviorism, an immediate reward for the desirable behavior would be the most successful strategy in changing the child's behavior. Answer A is incorrect because a behaviorist would not suggest removal of the desirable behavior as a method for encouraging the same behavior. Answer B is incorrect because, based on behaviorism, punishment for poor grades is not likely to improve study habits as effectively as positive reinforcement. Answer C is incorrect because promising the son a monetary reward is not as likely to improve his behavior because the reinforcement is not immediate. It is worth noting that reinforcement schedules do suggest that an interval schedule may improve results to the maximum level, but no answer choice is given that differentiates between reinforcement schedules.
Which physiological process prevents cross-species fertilization among hominids? A) Social constraints that prevent interspecies mating. B) Eggs fertilized with sperm from another species are always unviable. C) Cross-species fertilization results in polyspermy and death of the zygote. D) Species-specific receptors on the egg bind species-specific ligands on the sperm.
Choice D is correct. The mechanism that prevents cross-species fertilization is species-specific receptors expressed on the outside of the egg, which are bound by species-specific ligands expressed on the outside of the sperm. Answer D is therefore the correct answer. Social constraints may be a tempting answer because human beings would logically express social opposition to interspecies mating, but this is neither a physiological process, nor would it prevent fertilization if mating did occur contrary to social constraints. Eggs fertilized with sperm from another species do not always die, if the genetic material is almost identical. An example is the ability of a horse and a donkey to mate and produce a mule. Therefore, Answer B is incorrect. Answer C is incorrect because there is no reason to believe that polyspermy, or the fusion of more than one sperm with the egg, would automatically occur if a sperm and an egg were from two different species. It may also be helpful to note that only Answers A and D would actually prevent fertilization. Answers B and C allow for fertilization, but the fertilized egg or zygote is unviable. Because the questions stem asks for something that PREVENTS fertilization, this is another reason to dismiss choice B and C
The pyruvate dehydrogenase complex (PDH) is naturally inhibited by ATP because: A) ATP mimics pyruvate, acting as a competitive inhibitor for the ATP synthase enzyme. B) pyruvate is converted to ATP in a subsequent oxidation step, leading to feedback inhibition. C) enzymes of this class utilize ADP, rather than ATP, to dehydrogenate substrates. D) the PDH product generates ATP via the citric acid cycle, leading to feedback inhibition.
Choice D is the correct answer. The pyruvate dehydrogenase complex converts pyruvate to acetyl CoA, which enters the citric acid cycle, ultimately generating ATP and NADH. The NADH then donates electrons to the electron transport chain, generating ATP. If enough ATP is already present in the cell, it will inhibit pyruvate dehydrogenase in order to stop the production of more ATP. This is an example of feedback inhibition. Answer A is incorrect because ATP is not a competitive inhibitor of the PDH complex. ATP is considerably larger than pyruvate and would not be a good candidate for competitive inhibition. Answer B is incorrect because pyruvate is the substrate of the pyruvate dehydrogenase complex, not the product of it. Answer C is incorrect because dehydrogenases do not typically utilize ADP or ATP as cofactors
A study reports that women spend an average of 18 hours per week doing housework, while men spend an average of 10 hours per week doing housework. How can social conflict theory be used to explain this finding? A) Men, on average, work more hours outside the home, which balances out women's household work. B) Women do more household work because most women do not work outside of the home. C) Some women are not married, and therefore their inclusion in the study skews the data. D) The housework performed by women is an example of the "second shift" experienced by working women.
Choice D is the correct answer. The term "second shift" is a concept used within the conflict theory perspective to explain the unequal division of labor in the household between women and men. Answer A is wrong because, although this observation could be true, it does not explain the observation in the stem from a conflict theorist perspective. Answer B is wrong because research shows that women do work outside the home more today and this explanation does not suggest a conflict over the division of labor as social conflict theory would. Answer C is wrong because a skew in the data might explain the gender discrepancy in household work, but it is not related to social conflict theory.
Protein-based vaccines stimulate an immune response because they: A) bind glycans on the plasma membrane of foreign cells. B) recruit inflammatory cytokines and increase blood flow. C) stimulate T cells to produce antigen-specific antibodies. D) contain antigens similar to the antigens found on pathogens.
Choice D is the correct answer. Vaccines that are protein-based work because the antigens they contain resemble the antigens of the invading pathogen. For example, viral vaccines usually contain viral capsid proteins, and bacterial vaccines contain surface proteins. This allows the host immune system to initiate a primary immune response and prepare for a secondary immune response without an actual pathogen infection. Answer A is not correct because protein-based vaccines do not recognize glycans. This is a main theme from the first paragraph of the passage. Schistosomes are unique because it is the glycans on their membranes that interact with the host immune system, whereas in most cases immune responses are initiated in response to foreign proteins. Furthermore, vaccines are not intended to bind to foreign cells directly; they are intended only to stimulate the host immune system. Answer B is incorrect because it describes common components of a non-specific innate immune response, whereas vaccines utilize the antigen-specific nature of adaptive immunity. Answer C is false because antibodies are produced by B cells, not T cells.
During the repair of a DSB in human DNA, which nucleotide polymer is used as the homologous template? A) ssDNA in the nucleus B) DNA reverse transcribed from mRNA C) The template strand D) The sister chromatid
Choice D is the correct answer. When homologous recombination is used to repair a double-strand break, the template used is the sister chromatid. During this process, the recombination machinery seeks out DNA that compliments the overhangs on each side of the break, and the sister chromatid will have that exact sequence. The sister chromatid is not likely to be damaged in the same region that the broken DNA on the other chromatid, so incorporating DNA from the sister chromatid is an efficient method. Answer A is incorrect because there is no reserve of ssDNA in the nucleus. Answer B is incorrect because humans do not have a gene for a reverse transcriptase enzyme. Further, processed mRNA will no longer contain all of the bases that were present in the original DNA, so a reverse-transcribed DNA strand would be incomplete. Answer C is incorrect because the template strand is one of the two strands in double-stranded DNA, so in a double-strand break the template strand will have been removed or damaged.
Eukaryotic plasma membranes usually contain: I. carbohydrates. II. steroids. III. phospholipids. IV. proteins. A) III only B) III and IV only C) I, II, and III only D) I, II, III, and IV
D
If a patient's original lung volume (V1) is decreased by 33% (V2), what is the relationship between the total pressure in the patient's lungs before (P1) and after (P2) this change? A) P2 = 1/3P1 B) P2 = 2/3P1 C) P2 = 3P1 D) P2 = 3/2P1
D
Long-term potentiation (LTP) refers to changes in the strength of a nerve synapse that are necessary for long-term memory storage. Which neurotransmitter system is most likely implicated in LTP?
Glutamate
What is intersectionality?
Intersectionality suggests that the interconnected nature of social categorizations such as race, class, and gender create overlapping and interdependent systems of discrimination or disadvantage
What is miscegnation?
Miscegenation refers to the mixing of racial and ethnic groups in intimate relationships.
Do molecules without chiral centers undergo polarized light?
NO! Only chiral centers (which must be determined experimentally)
Are inner or outer hair cells of the cochlea responsible for mechanical amplification?
Outer
What is the Expectancy Value Theory?
The Expectancy-Value Theory of motivation suggests that motivation is related to the interplay of two primary factors: 1) the individual's perceived likelihood of success and 2) the relative value of the rewards likely to be associated with success.
Which theory of emotion best predicts how the study actors will feel after demonstrating nonverbal expressions of happiness?
The Facial Feedback Hypothesis- The facial feedback hypothesis is the theory suggests that the physical expression of an emotion also activates the experience of that emotion. Therefore, expressing a 'happy' body language in one's face should engage the experience of happiness within the person making those expressions.
What do valence and arousal code for?
Valence codes for events as positive or negative emotions -Angry= negative; Happy= positive Arousal codes for fight or flight responses Positive= high arousal (alert, jumpy, stressed out, excited) Negative= low arousal (tired out, calm, relaxed)
Small batteries are used to provide electrical power for pacemakers. How does the current (I) supplied by the pacemaker battery relate to the load resistance (R) in the pacemaker circuit?
Voltage, current, and resistance are related through Ohm's Law: V = IR. A battery holds the voltage constant. Therefore, current and resistance have a linear inverse relationship.
What is the difference between Z and E configurations?
Z= highest priority groups are on the same side E= highest priority groups are on opposite sides
What is symbolic racism?
coherent belief system that can be expressed in several beliefs: that Blacks no longer face much prejudice or discrimination, that Blacks' failure to progress results from their unwillingness to work hard enough, that they make excessive demands, and that they have gotten more than they deserve.
What does the fluid mosaic model state? What type of amino acids is the transmembrane composed of?
he fluid mosaic model states that cellular membranes consist of a lipid bilayer populated by peripheral and integral membrane proteins. A chloride channel will allow chloride ions to pass from one side of the membrane to the other, so it must be a transmembrane integral protein. Transmembrane proteins consist of hydrophilic or polar amino acids at both ends of the protein, which associate with the extracellular and cytosolic fluids, which are both hydrophilic. However, for the protein to remain dissolved within the hydrophobic center of the lipid bilayer, the core of the membrane protein must contain a sufficient number of hydrophobic (non-polar) amino acids. Finally, when the transmembrane protein is an ion channel, the surface of the channel formed through the membrane must also contain hydrophilic residues in order for charged ions to easily pass through the channel.
An anomeric position of a sugar is called what?
invertible epimer
Define the term "glass ceiling"
women face serious barriers to obtaining positions in management positions.