NS 4

Assuming no alternative splicing occurs, approximately how many base pairs will be in a mature mRNA produced from the FAM83H gene? A. 1221 B. 1441 C. 1939 D. 2079`

WOW you confused what alternative splicing is. B is correct. A mature mRNA consists of a 5'-cap (one base pair), the 5' UTR, coding regions, the 3' UTR, and a poly(A) tail. Therefore, the length of a mature mRNA using the numbers given in Table 1 is: 1 + 130 + 300 + 250 + 150 + 180 + 200 + 90 + 140 = 1441. A: This answer choice neglects to include the 5'-UTR and the 3'-UTR. These regions have a significant influence on translation, so they certainly must be transcribed and end up in the mature mRNA product. Note also that these regions are distinct from the coding regions, since the UTRs typically do not end up in the final protein product. C, D: Values this large can only have been obtained if introns were included in the calculation. Remember, introns are spliced out during post-transcriptional modification and are not found in the mature mRNA!

Dynein

is a motor protein that moves cellular "cargo" along microtubule "train tracks."

Combined with passage information, which of the following results in an E9.5 respiration mixture would strengthen the hypothesis that the cell's metabolism is exclusively anaerobic?

READ THE QUESTION! The goal was to pick one that strengthens the hypothesis. D is correct. From Table 1 and the results of the test shown in Figure 2, inhibitors of Cx1, Cx2, and Cx4 do not change the rate of oxygen consumption in the respiration mixture containing E9.5 homogenate. If it were further shown that O2 use remains unchanged after addition of glutamate or succinate, this would continue to imply that the cell's metabolism is anaerobic, since neither stimulating nor blocking complexes of the ETC - the principal pathway by which ATP is formed aerobically in the cell - effects a change in cellular oxygen consumption. A, B: If the cell's metabolism were anaerobic, oxygen consumption would be unlikely to vary with the cellular ADP concentration or due to ETC inhibition. C: While this may be true if the cell's metabolism is anaerobic, it may also be true of aerobic metabolism. Under most conditions, the rates of electron transport, oxygen consumption, and ATP synthesis are tightly coupled to one another, as well as to the availability of ADP and inorganic phosphate.

Reciprocal altuism

Reciprocal altruism is a situation in which you help a person based on the expectation that they will in turn help you in the future.

Surround suppression

Surround suppression involves perceiving tactile information while ignoring stimuli immediately surrounding it

Symbiotic relationships

Symbiotic relationships are relationships between two individuals (or organisms) in which both need each other to survive.

Titin

Titin is a giant protein, greater than 1 µm in length, that functions as a molecular spring which is responsible for the passive elasticity of muscle. It is composed of 244 individually folded protein domains connected by unstructured peptide sequences.

Hypoventilation can lead to? What about Hyperventilation?

Acidocis and Alkilosis respectivily

In the U.S. population, the frequency of the allele for colorblindness, Xc, is 8%. Which of the following is the frequency of colorblind women and colorblind men in the population, respectively? A. 8%, 0.64% B. 0.64%, 4% C. 0.64%, 8% D. 64%, 8%

C is correct. For a woman to be colorblind, she must get two copies of the Xc gene. Since the frequency of this gene is 0.08, the odds of being homozygous for the gene are 0.0064, or 0.64%. Males only need a single copy of the Xc gene to be colorblind (since their other gene is Y), making the odds of a male being colorblind 8%. A, B, D: These answer choices are the result of miscalculation.

Collage is found in?

Collagen is a primary component in connective tissue, such as that found in the tendons, cartilage, and blood vessels

A student has just begun medical school and is seeing a patient with two third-year students. When the attending physician asks his opinion on the diagnosis, he states that he agrees with what the older students already said. Which of the following best describes the most likely reason for his response? A. Informative pressure B. Normative pressure C. Conformity pressure D. Groupthink

A is correct. Informative pressure is a subtype of conformity pressure. It occurs when an individual conforms his or her behavior to match that of the rest of a group out of the belief that the group is better informed and knows more than the individual. The medical student most likely believes that because he has only been in medical school a few weeks, the third-year students know more than he does. B: Normative pressure is a subtype of conformity pressure in which the individual knows that the others are incorrect, but still feels pressure to not dissent from the rest of the group. Since this pressure does not arise out of a belief that others know more, it is less likely than choice A based on this situation. C: The situation described is a type of conformity pressure, but option A is more specific. The question asks which of the following "best describes" the scenario. D: Groupthink refers to decision-making becoming more irrational or dysfunctional as a group increases in size. This does not accurately describe the situation above.

Some Kathoey have trouble relating to society around them and feel trapped by institutions and bureaucratic policies that fail to give them equality, a situation commonly known as the "iron cage." Which sociological thinker developed the concept of the iron cage? A. Max Weber B. Karl Marx C. Émile Durkheim D. Friedrich Engels

A is correct. Max Weber's theories of symbolic interactionism emphasize how individuals relate to society, and one of his ideas was the concept of the iron cage. He believed that the experience of the "iron cage" led to disenchantment with society. B: Karl Marx was an economist and philosopher and is closely associated with the ideas behind Marxism/communism. Within the realm of MCAT psychology and sociology, Marx is associated with conflict theory, one of the main theoretical approaches to sociology. Marx did not propose the idea of the "iron cage," so this option is incorrect. C: Émile Durkheim was a French sociologist who studied and wrote about topics ranging from religion to suicide. However, Durkheim did not develop the concept of the "iron cage." D: Friedrich Engels, a German philosopher, was best known for his work in collaboration with Karl Marx. As such, he has nothing to do with the proposal of the concept of the "iron cage."

Difference between a mediating and moderating variable

A mediating variable is one which explains the relationship between two other variables. Here, emotion explains the relationship between competence group and behavior. A moderating variable is one which changes the relationship between two variables. There is no indication that the level of emotion changes the strength of the relationship between group and behavior. Can strengthen.

Behaviorists would assert that self-defeating behaviors are maintained by immediate reinforcement in the form of: A. relief from anxiety. B. defending the ego. C. negating one's self-image. D. increasing existential anxiety.

A is correct. People are more likely to behave in a self-defeating or destructive manner either when they perceive a threat or when they have low self-esteem. These people are more likely to be susceptible to having anxiety and emotional distress, which are problems that are usually directly related to a less favorable self-appraisal. Self-defeating or self-destructive behaviors often manifest due to an inability to handle either anxiety or stress which results from a lack of self-confidence. Thus engaging in these behaviors offers an immediate relief from anxiety which then reinforces that behavior. B: Self-defeating behaviors are those that sabotage the self. This is very different from ego defense mechanisms, which include projection, rationalization, regression, etc. and which serve to protect the ego. C: This question asks about reinforcement, or a good/pleasant response to a behavior that causes us to continue performing that behavior. Negating (nullifying or canceling out) characteristics of one's self-image is not pleasant or likely to reinforce any behavior. D: Similarly to choice C, increasing existential anxiety is an unpleasant experience and would not serve as reinforcement. ("Existential" means "related to one's own existence," although that is not necessary to know here.)

Arinya is a new transgender female who seeks the help of other Kathoey in her community. She asks them to help her adopt new feminine behavior, roles, and expectations, and remove masculine behaviors and aspects of her identity. This process is known as: A. resocialization. B. anticipatory socialization. C. moral development. D. poor socialization.

A is correct. Resocialization is the process of removing the behaviors and roles we have developed over time and replacing them with newly-learned behaviors and roles. B: Anticipatory socialization is when we prepare for future life roles. For example, before her transition, Arinya may have prepared herself for her future life as a Kathoey. C: Moral development is the way that people learn what is considered "good" and "bad" in their society. D: Socialization is a process we go through over time as we learn to understand norms, expectations, beliefs, and values. Arinya's process involved learning new norms, expectations, beliefs, and values while discarding old socialization, so D is incorrect.

Zoologists discover a new species of lizard with a low degree of sexual dimorphism. Which of the following behaviors would the researchers most expect to find exhibited by members of this species? A. Repetitive mating between monogamous pairs of lizards B. Helping by juvenile relatives of lizards with young offspring C. More complex courtship rituals than other, similar species D. Males building large, ornate nests to attract females

A is correct. Sexual dimorphism refers to the degree to which males and females resemble each other. A species with low sexual dimorphism contains males and females that look mostly identical. High sexual dimorphism signals intense competition for mates, while animals from species with low sexual dimorphism typically form pair bonds and mate for life. B: Alloparenting, or caretaking of offspring by individuals other than the biological parents, is not related to dimorphism. C, D: These are traits that one would expect from a species with intense mate competition.

Which of the following is most likely true of the 5'-UTR region of the FAM83H gene? A. It is transcribed, but is typically not translated or is only partially translated. B. It is always both transcribed and translated. C. It is neither transcribed nor translated. D. It is cleaved from the pre-mRNA transcript as part of a post-transcriptional modification.

A is correct. The 5'-untranslated region (5′-UTR) is the region of mRNA that is directly upstream from the initiation codon. This region is important for the regulation of translation of a transcript; from this information alone, we know that the 5'-UTR must be transcribed (eliminating choice C). However, as it is the "untranslated" region, we can conclude that this region is not translated or only partially translated into a protein (eliminating B). B: The 5'-UTR is not always translated. In fact, it typically is not translated, hence its name. C: The 5'-UTR is transcribed. D: Since we know this region influences translation, it must still be present in the mature mRNA formed as a result of post-transcriptional modification.

Which of the following changes would most likely be found in patients with mitochondrial myopathy? A. Muscle aches due to lactic acid buildup B. Diabetes-like symptoms due to elevated plasma glucose concentration C. Increased rate of mitosis D. Increased energy production

A is correct. This is a question about the citric acid (Krebs) cycle and where cytochrome c oxidase fits in. Actually, the passage provides a reminder that this enzyme is involved in the electron transport chain, which regenerates NAD+. If less effective at this, the work will be taken up by the lactic acid fermentation process (in fact, this happens after a heavy work-out when enzymes are unable to keep up with all the by-products of the accelerated metabolism, so you can also reason that less effective enzymes will lead to a similar effect even if you don't know the citric acid cycle that well). So a surplus of lactic acid, i.e., the pain of lactic acidosis, is likely to be another symptom of mitochondrial myopathies. B: Patients with mitochondrial myopathy still perform glycolysis relatively normally, and nothing in the passage implies that glucose uptake is affected by this disease. C: Mitosis, or cell division, is unlikely to be directly affected by mitochondrial myopathy. We certainly would not expect the rate of mitosis to be increased (as in cancer). D: This is the opposite of the likely affect of mitochondrial myopathy.

A researcher's agar plate becomes partially contaminated with an unknown contaminant. When growing a culture of gram-negative bacteria on the plate, only the area with the contaminant is clear the next morning. The contaminant is most likely: A. a phage in the lytic phase. B. a nutrient broth lacking an essential nutrient for the bacteria. C. a phage in the lysogenic phase. D. distilled water. Remember that Lytic and Lyse have nearly the same letters despite lysogenic sounding like lyse

A is correct. Whatever has contaminated the plate is killing the bacteria, preventing them from growing into the contaminated region. A virus in the lytic phase will infect and kill, or lyse, bacteria. The lytic phase/cycle can be contrasted with the lysogenic cycle, during which the virus does not kill the infected bacterium. These two cycles are shown below. B: The agar itself has the necessary nutrients, since the bacteria aren't growing just where the contaminant is. Thus, adding some extra unnecessary nutrients wouldn't stop growth. C: Again, in the lysogenic phase, a virus incorporates into the bacterial genome and allows the bacteria to grow and reproduce. Since a virus in this phase does not kill the bacteria, it would not explain the clear area on the agar plate in this question. D: Distilled water would likely just diffuse across the plate and is unlikely to be so toxic as to prevent all growth.

Stimulus motives are: A. needs that are learned, such as the need for power or for achievement. B. innate but not necessary for survival. C. not innate but necessary for survival. D. innate and necessary for survival.

B is correct. A stimulus motive is defined as a motive that appears to be unlearned but causes an increase in stimulation, such as curiosity. These motives are not necessary for survival. A: Stimulus motives are not learned. C, D: Stimulus motives are not necessary for survival. For example, imagine a cat who lives inside an apartment. One of the cat's stimulus motives is the desire to explore his environment (for example, walk around the apartment, jump inside cupboards or cabinets, etc.). This is not necessary for survival — the cat could easily survive simply by sitting in one place and moving only to acquire food or water. Instead, this motive can be thought of as primarily for the cat's stimulation or entertainment.

Which of these statements, if observed in the early embryo, best explains changes in ATP generation thought to occur during rat cardiac embryonic development? A. Energetic demands are greatest early in development. B. Oxidative phosphorylation is limited by physiological hypoxia. C. Maternal oxygen tension is high. D. Mitochondrial mass is greatest early in embryogenesis.

B is correct. According to the first paragraph of the passage, "the early embryonic heart is thought to generate ATP exclusively anaerobically. During the late embryonic period, beginning at approximately embryonic day (E) 12, a transition to aerobic glycolysis occurs, which is followed by a switch to β-oxidation after birth." A potential explanation for this transition is that early in development, oxidative phosphorylation - required for both aerobic glycolysis and the generation of ATP from β-oxidation - is limited by a lack of available oxygen, forcing metabolism to occur via an anaerobic pathway. A: This does not provide a possible explanation for the switch from anaerobic to aerobic metabolism. Furthermore, in mammals, aerobic modes of metabolism tend to be more efficient than anaerobic ones. If the energetic demands of the embryo declined from the earliest stages of development, it is unlikely that this would precipitate a change to a more robust metabolic mode. C: Fetal oxygen is dependent on the supply of oxygen from maternal blood, and while a statement that maternal oxygen tension is high does not necessarily correspond to the oxygenation state of fetal blood, it does not imply fetal hypoxia. D: Such a condition is associated with the potential for an aerobic mode of respiration early in fetal development.

To compare the percent of people experiencing crime in an area with the percent of people perceiving crime to be a problem, researchers could use what type of analysis? A. A paired samples t-test B. An independent samples t-test C. Linear regression D. A Pearson correlation coefficient

B is correct. An independent samples t-test is conducted when researchers wish to compare mean values of two groups. A: This test would be used if the results came from the same participants. C: Linear regression is used to predict scores from independent variables. D: A Pearson correlation coefficient is calculated to compare the association between two variables.

A pregnant couple is worried that their child will develop AI. Their respective genealogies are shown below. What is the probability that the first child of this couple will develop non-ENAM-related AI? Image A. 1/16 B. 1/9 C. 1/2 D. 8/9

B is correct. In Figure 1 and, more importantly, in the figure in the question stem, we can see that there is an instance of two unaffected parents having an affected child. We can also see that the trait is found equally in males and females. This means that the trait is inherited in an autosomal recessive fashion. We now know that each of the couples' parents are heterozygous carriers of the AI gene. This means each parent in generation 1 has a 50% chance of passing on their affected gene. Neither member of the couple is affected, but they may be carriers. If we designate "A" as the wild-type allele and "a" as the mutated allele, then (as shown in the Punnett square below) the probability that each member of the couple is a carrier is 2/3. The probability is NOT 1/2, because the only possible genotypes of the couple are AA and Aa. Image In order for the couple to have an affected child, both would need to be carriers. Thus the odds that they both are carriers is 2/3 x 2/3 and they would need to pass their mutated allele (not the healthy allele) to their child. If they were both carriers, the probability they would have an affected child is ¼. Therefore, the probability of the child with the '?' being affected by AI is (2/3)(2/3)(1/4) = 4/36 = 1/9. A, C, D: These answer choices are the result of miscalculation.

Thai beliefs about non-normative gender identities may stem from indigenous spiritual creation stories and traditions that asserted there are three sexes - male, female, and male-female. What term best describes this phenomenon? A. Cultural universal B. Non-material culture C. Material culture D. Counterculture

B is correct. Non-material culture refers to the ideas, beliefs and attitudes of a society; beliefs about non-normative gender identity are considered part of the non-material culture. A: Cultural universals are patterns or traits that are shared by all societies around the world. This belief is very specific to people from Thailand, so it is not a cultural universal. C: Material culture refers to the physical objects or belongings of individuals in a particular society. D: A counterculture is a small group within a culture that challenges or rejects the norms and values of the majority from the larger culture.

Which of the following would best explain the observation that pyrivinium is more effective against BP-CML than colon cancer? A. Colon cancers rely more on MR for energy production than many other cancers. B. Colon cancers rely less on glycolysis for energy production than BP-CML. C. BP-CML is a slower-growing type of cancer than colon cancers. D. Pyruvinium is absorbed into the mitochondria of colon cancer cells.

B is correct. Paragraph 2 tells us that pyrivinium is effective against cancers in glucose-starvation conditions. If colon cancers rely less on glycolysis (and thus would be less directly affected by glucose-starvation conditions) then we would expect pyrivinium to be less effective against colon cancers, and thus more effective against BP-CML. A: The phrase "many other cancers" is too vague to directly address the issue in the question - a comparison of BP-CML and colon cancers. C: The first paragraph implies that drugs like pyruvinium are effective because they can target the highly metabolic cancer cells over healthy cells. For this reason, if BP-CML were a slower-growing cancer than colon cancer, we would expect pyruvinium to be less effective against BP-CML. This is the opposite of the statement that we are trying to support here. D: This statement may be true, but it certainly does not explain why pyruvinium is more effective against BP-CML than against colon cancer.

It has been shown that pheromones induce the body to secrete sex hormones more readily. All of the following are expected effects of sex hormones EXCEPT: A. estrogen causes the endometrial lining to thicken. B. testosterone causes the Leydig cells in the seminiferous tubules to produce sperm. C. estrogen inhibits bone resorption. D. testosterone causes the development of secondary sex characteristics in boys.

B is correct. Sperm is produced by the Sertoli cells of the seminiferous tubules, not the Leydig cells. The seminiferous tubules and their location in the testes of the male reproductive system are shown below. A: This is true; estrogen and progesterone together cause the endometrium to thicken. Estrogen produced from the developing follicles stimulate endometrial growth, and progesterone is responsible for converting the estrogen-primed endometrium into a receptive state. C: Estrogen does inhibit bone resorption; in fact, this is the reason why post-menopausal women experience significant declines in bone density. D: This is also an accurate statement; testosterone causes secondary sex characteristics to develop during puberty in boys.

If a group of individuals diagnosed with personality disorder were found to believe that their socially destructive actions should have yielded neutral or positive social results with those around them, it would best support which personality theory? A. Humanistic perspective B. Social cognitive perspective C. Behaviorist perspective D. Biological perspective

B is correct. The correct answer must explain the behavior of the subjects in terms of their expectations of others. The social cognitive perspective is based upon expectations of others. A: The humanistic perspective is centered on the use of free will and how to best apply it, which would not apply in this case. C: The behaviorist perspective is related to external stimuli experienced by the person. Since this question stem focuses on the predicted experiences of others, this does not apply here. D: The biological perspective is based on biological inheritance, which is irrelevant to this scenario.

Which of the following could NOT explain a patient who presents with a blood pH of 7.0? A. Anaerobic respiration leading to lactic acid buildup B. Hypoventilation C. Carbonic anhydrase working only in the reverse direction D. Underproduction of bicarbonate

C is correct. A blood pH of 7.0 is very low (lower than typical physiological pH, which is 7.4 according to paragraph 2). Thus, it must be attributed to a mechanism that will increase hydrogen ion concentration. Therefore, the correct answer will be one that would have an opposite effect on pH or no effect. We learn from the passage that carbonic anhydrase catalyzes the reaction in Equation 1 (shown below). If carbonic anhydrase only worked in the reverse direction, there would be more CO2 and H2O, and less H+, in the blood. Therefore, blood pH would increase. A: This would result in a decreased pH because lactic acid is acidic. B: We are told in the passage that hypoventilation could result in respiratory acidosis. This would lower the pH. D: Bicarbonate is a weak base, so decreased bicarbonate production would be expected to make the blood less basic. This would help explain the acidosis (decreased pH) described in the question stem.

If an Arab IMG received an unflattering nickname from coworkers due to his tendency to forget English medical terms, this would be an example of: A. positive reinforcement. B. negative reinforcement. C. positive punishment. D. negative punishment.

C is correct. A punishment is intended to discourage a behavior from being repeated (in this case, forgetting English medical terms.) A positive punishment adds an unpleasant consequence that was not previously present to do this (in this case, an unflattering nickname.) A: Positive reinforcement adds a pleasant consequence that was not previously present in order to encourage a behavior to be repeated. B: Negative reinforcement removes an unpleasant factor that was previously present to encourage a behavior to be repeated. D: Negative punishment removes a pleasant factor that was previously present to discourage a behavior from being repeated.

A classic example of me not paying attention to the details The results in Table 1 suggest: A. that only a small portion of Z mRNA is translated to protein. B. that pre-transcriptional control of gene expression is of primary importance in regulating cytokine Z. C. that post-transcriptional control of gene expression is of primary importance in regulating cytokine Z. D. that cytokine Z gene expression is poorly regulated.

C is correct. In examining Table 1, you should notice that the plasma concentrations of Z increases far more than the concentrations of Z pre-mRNA during exercise. This implies that the rate of transcription is not increasing as much as the rate of translation due to exercise; if pre-transcriptional control was most important to the exercise mechanism, the concentrations of pre-mRNA would increase more significantly. This indicates that the regulatory mechanism that causes plasma [Z] to increase does so by increasing the translation of Z, not its transcription. This is referred to as post-transcriptional control. A: This is the opposite of what is occurring; the skyrocketing levels of cytokine Z suggest that virtually all of the mRNA is being translated. B: If pre-transcriptional control were important in regulating Z, much more mRNA would be present post-exercise. D: There is nothing in the passage to suggest that cytokine Z gene expression is poorly regulated. In fact, the evidence shows that there is a level of control related to physical activity.

Defects in which of the following proteins would most likely lead to loss of structural integrity in skin epithelial cells? A. Microtubules B. Titin C. Intermediate filaments D. Myosin

C is correct. Intermediate filaments such as keratin are directly responsible for structural integrity in skin. A: Microtubules are not involved in structural integrity, but in mitosis, meiosis, cell trafficking of vessels, and ciliar/flagellar motion. Microtubules are composed of tubulin protein dimers, as shown below. B: Titin is a component of muscle. D: Myosin is a motor protein.

During an isoelectric focusing procedure, cytokine Z migrated closer to the cathode than the control protein. This is most likely because Cytokine Z has a higher concentration of which amino acid? A. D B. E C. K D. T Even if you forget the charge of the cathode in IEF, rationalize what the answer is. The other 3 are negatively charged so how could you differentiate between them? You can't!

C is correct. Isoelectric focusing (IEF) is used to separate proteins by isoelectric point, which depends on the amino acid composition of the protein. In an IEF setup, the cathode is the negatively-charged electrode. Because Z migrated closer to the cathode than the control protein, it likely has a larger net positive charge than the other protein. Therefore, it would experience a greater electrostatic attraction towards the cathode. Lysine (K) is the only positively charged amino acid listed, so it must be correct. A, B: Aspartic acid (D) and glutamic acid (E) are negatively charged at physiological pH. Note that since both of these amino acids have extremely similar charge properties (and since both answers cannot possibly be correct at once), we can eliminate both even if we do not fully understand isoelectric focusing. D: Threonine (T) does not carry a charge at physiological pH.

A person with intact mirror neurons would be expected to perform similar to a person with mirror neuron dysfunction on: A. an assessment of theory of mind. B. an assessment of empathy. C. an assessment of tactile perception. D. an assessment of another individual's repeated behavior.

C is correct. Tactile perception involves perceiving information related to touch, not an activity which requires observation and understanding of others. A: Theory of mind involves being able to take another person's perspective, an activity that would involve mirror neurons. B: Empathy involves being able to understand another person and relate to that person's experience. D: This assessment would involve an action very similar to what was described in the studies, which involves mirror neurons

Which of the following is a mental process that could explain the findings about the relationship between emotion and behavior? A. Stereotype threat B. Cognitive dissonance C. Affect heuristic D. Anchoring

C is correct. The affect heuristic is the process of making a judgment based on emotions that are evoked. A: A stereotype threat occurs when an individual's behavior changes based on perceived negative stereotypes about himself or herself. B: Cognitive dissonance happens when a person's beliefs and reality do not match, or when beliefs conflict with other beliefs. D: Anchoring is the act of relying too much on the first information encountered.

Which of the following best describes why hyperventilation would lead to a decreased blood CO2 concentration? A. The rate of CO2 production in the cells exceeds the rate of CO2 exhalation. B. The rate of CO2 exhalation exceeds the rate of CO2 inhalation. C. The rate of CO2 exhalation exceeds the rate of CO2 production in the cells. D. The rate of CO2 excretion in urine exceeds the rate of CO2 in the cells.

C is correct. The main source of CO2 in the human body is cellular production during the Krebs cycle. If an individual breathes very rapidly, he will exhale CO2 more quickly than his cells produce it. This leads to an unusually low concentration of carbon dioxide in the body, which correlates to a higher blood pH (alkalosis). A: This would explain the opposite of the situation described in the question stem. B: Inhalation of CO2, which has a very low concentration in air, is not a significant source of CO2 in blood. D: This doesn't relate to exhalation or inhalation. Remember, the question stem asked about hyperventilation.

A research subject is shown the following list of the following words: wing, engine, tail, and window. When later presented with and asked to recall whether the presented word was on the original list, the participant identifies "runway" as having been on the list. This is an example of: A. the context effect. B. a miss. C. a false alarm. D. déjà vu.

C is correct. The subject is primed with airplane-related words, then incorrectly identifies another airplane-related word as having been a part of the list. This is a false alarm because the participant incorrectly responds positively when the stimulus was in fact not present. The concept of a false alarm is part of signal detection theory, which focuses on the mechanisms by which individuals detect certain stimuli over others. The diagram below shows a false alarm in relation to other concepts from signal detection theory, in the context of the question stem. A: Do not fall for this answer simply because the word "context" looks correct here! In psychology, context effects refer to increased recall when the subject is in a similar environment as the one in which the original learning took place. B: A "miss" implies that the stimulus was indeed present on the list, but the participant did not recognize it. D: Déjà vu is an example of a context effect in which a person believes he has experienced an event before.

By approximately what percentage of its original length is a free DNA strand shortened by the coiling around a single histone? (Note: A histone has a diameter of 11 nm; assume inter-histone length is negligible.) A. 25% B. 50% C. 75% D. 100%

C is correct. This question asks us to determine how much each histone shortens the DNA strand. We can imagine this linking as winding a string around a tennis ball. From paragraph 3, we know that 200 nucleotides wrap around 1 histone. Initially, a 200-nucleotide sequence will be 200 (0.3 nm) = 60 nm in length. Once coiled around the protein, we can assume (without getting into unnecessary surface area calculations) that a single layer of DNA strand will be wrapped around the protein (strand thickness = 2 nm), meaning we now have the strand condensed to a ~ 4-nm layer (2 nm on each side) around the 11-nm-diameter protein. Thus, about 60 nm of DNA is replaced by 15 nm, meaning there is approximately a 45-nm decrease in length. 45/60 = 0.75 = a 75% decrease in length. A, B: These answers are the result of miscalculation. D: This is impossible, as a 100% decrease in length would mean the DNA strand was 0 nm after histone coiling.

It was discovered that in those whose stress levels are significantly elevated by traumatic events, the incidence of bedwetting was increased. During which stage of sleep is bedwetting most likely to occur? A. 1 B. 2 C. 4 D. REM

C is correct. Typically, sleepers pass through five stages: 1, 2, 3, 4, and REM (rapid eye movement) sleep. Stage 4 is referred to as Delta sleep because of the delta waves that occur during this stage. Stage 4 is a deep sleep that typically lasts about 30 minutes. Sleepwalking and bed-wetting typically occur at the end of Stage 4. During this "deep sleep," there is no eye movement or muscle activity. This is when some children may also experience sleepwalking, or night terrors. A: Stage 1 represents light sleep, where one drifts in and out of sleep and can be awakened easily. In this stage, the eyes move slowly and muscle activity slows. B: In stage 2 sleep, eye movement stops and brain waves become slower, with only an occasional burst of rapid brain waves called sleep spindles. D: During REM sleep, breathing becomes more rapid, irregular and shallow; eyes jerk rapidly, and limb muscles are temporarily paralyzed. Brain waves during this stage increase to levels experienced when a person is awake. Also, heart rate increases, blood pressure rises, and the body loses some of the ability to regulate temperature.

In humans, the quadriceps muscle is a skeletal leg muscle under voluntary control. As such, it contracts in response to signals from the motor cortex in the cerebrum. If such a muscle contracts involuntarily, that indicates: A. a pathological hyperpolarization of the nerve innervating the muscle. B. an appropriate modulation of Ca2+ ions in the muscle tissue. C. the operation of a reflex arc. D. significant sodium efflux from the neuron.

C is correct. Voluntary muscles may contract involuntarily due to a reflex arc. The classic example is the patellar tendon reflex, in which sudden stretching of the patellar tendon leads to an involuntary contraction of the quadriceps. Such contraction occurs before the signal has even reached the brain. A typical reflex arc is shown below. This arc contains a sensory neuron, which carries sensory information from peripheral receptors toward the spinal cord, and a motor neuron, which carries a signal from the spinal cord to an effector muscle. This particular reflex arc also contains an interneuron, which is a neuron within the spinal cord that synapses on both the sensory and motor neurons, connecting them.

In the first trial of the PCR procedure, only one primer was added to the mixture. What was the most likely outcome during this trial? A. Both of the DNA strands were linearly amplified. B. Only one strand of the DNA was exponentially amplified. C. Only one strand of the DNA was linearly amplified. D. PCR amplification was unable to proceed.

C is correct. When performing PCR, if only one primer is added to the mixture, then that primer will bind to one of the strands and initiate replication of that strand to produce the complementary strand. For one double-stranded template DNA molecule, after one cycle, we are left with two of the complementary strand while still having only one of the strands where the primer binds. In the next cycle, the primer again binds to the strand to which it is complementary. Therefore, only the complementary strand will be replicated again; this time we have three of the complementary strand. As you can see here, one of the strands is being replicated linearly (1 → 2 → 3 →...n), while the other strand is not replicated at all. After 30 cycles, for example, assuming that we began with one copy of each strand, we would have 30 copies of one strand and only one copy of the other. This differs from PCR that includes two primers (which is typical), where we would expect exponential amplification (230 copies of each strand). A: Only one of the primers is added to the mixture, so one of the strands will not have a primer to be replicated. B: The amplification is linear, not exponential (2n copies would be produced after n cycles), as explained above. D: PCR amplification will operate because one of the strands can still be replicated.

It can be inferred that researchers chose the emotions cited in the study because: I. the emotions are distinct from one another. II. the emotions are culturally bound. III. the emotions are associated with certain behaviors. A. I only B. II only C. I and II only D. I and III only

CULTURALLY BOUND means to be confined to a single culture! Could have got this one correct! A is correct. The passage states that each of the emotions activated a separate part of the brain. This suggests that the emotions are distinct. II: The passage stated that the emotions were universal across cultures, not culturally bound (or confined to a single culture). III: This was a finding that emerged in the study, but it was not initially anticipated. B: RN I is correct, while RN II is incorrect. C: RN II is incorrect. D: RN III is incorrect

Cadherins roles in adhesion

Cadherins are transmembrane proteins which play a primary role in cell-to-cell adhesion (remember that C stands for cell-to-cell), forming adherens junctions to bind cells within tissues together. They would not play a role in the cell-to-extracellular matrix interactions required to bind the macrophages to collagen or fibronectin.

Difference between cohesion and adhesion

Cohesion involved an attraction between the same type of molecule while adhesion involves an attraction between 2 different type of molecules.

Researchers discover another cytokine (X) that is upregulated even more than Z as a result of exercise. Cytokine X binds to receptors in skeletal muscle to stimulate angiogenesis. After strenuous exercise, local [X] would be LEAST similar to post-exercise [Z] in: A. subjects in Group D. B. subjects in Group C. C. subjects in Group B. D. subjects in Group A.

D is correct. After you exercise, your body repairs or replaces damaged muscle fibers by fusing muscle fibers together to form new muscle protein strands (myofibrils). These repaired myofibrils increase in thickness and number to create muscle hypertrophy. These larger muscles require additional blood vessels. If cytokine X acts to promote angiogenesis in the new muscle tissue, this means we would expect large increases in the local concentration of X. Thus the group that is LEAST similar to this large increase in local [X] would be the group with the smallest increase in [Z]. That's group A. B, C, D: Groups B, C, and D did not have as small an increase in [Z] during exercise compared to group A.

A much-feared outcome of Alzheimer's disease is: A. functional psychosis. B. paranoia. C. general paresis. D. senile dementia.

D is correct. Dementia is a loss of brain function that occurs with certain diseases. Alzheimer's disease is one form of dementia that gradually gets worse over time. It affects memory, thinking, and behavior. A: This is a a severe emotional disorder characterized by personality derangement and loss of ability to function in reality, but without evidence that the disorder is related to the physical processes of the brain. This is not associated with Alzheimer's. B: Paranoia is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. This is not associated with Alzheimer's. C: General paresis is one form of neurosyphilis, an infection of the brain or spinal cord. It usually occurs in persons who have had untreated syphilis for many years. This is not associated with Alzheimer's.

Arrange the following in increasing order of compactness. I. Nucleosome II. Heterochromatin III. Euchromatin IV. DNA helix A. IV, I, II, III B. III, I, II, IV C. I, III, IV, II D. IV, III, II, I

D is correct. Examining the choices, we can see right away that a DNA helix will be the least compact structure given and should be listed first (eliminate choices B and C). Now we need only to compare the remaining structures. Beginning with structure I (a nucleosome), note that according to the information in paragraph 3, nucleosomes are approximately 11-15 nm in diameter. These form the fundamental repeating units of eukaryotic chromatin, meaning that they are more compact than either chromatin structures and should be listed last. At this point, we have our answer. However, if you look further, you must remember that chromatin is primarily the combination of DNA and histones, the proteins responsible for packaging DNA into smaller volumes so that they can fit inside the cell. There are two varieties of chromatin: euchromatin and heterochromatin. Heterochromatin is formed from compactly coiled regions, while euchromatin is loosely coiled. Thus, II is more compact than III. A: "Increasing order of compactness" means "least compact to most compact." Knowing this, we can see that this option incorrectly states that euchromatin (III) is more compact than heterochromatin (II). B: Heterochromatin is less compact, not more compact, than a single nucleosome. Also, the DNA helix (IV) should be the least compact structure of the four, as DNA is not compact unless it is associated with histone proteins. This choice incorrectly states that the DNA helix is the most compact option. C: Again, the DNA helix (IV) should be the least compact option and should be listed first.

Which additional control experiment would allow the researchers to conclude that the macrophage migration differences in NCM and ACM are due primarily to chemoattractant in the medium? A. No additional experiments are needed to reach this conclusion. B. The NCM and ACM should be analyzed by MALDI-TOF spectroscopy to ensure that the protein sequence of the chemoattractant is not the same in the NCM and the ACM. C. The NCM and the ACM should be filtered to remove all protein, and the filtrates should be used to repeat the experiment. D. The migration of both CA and AA phenotypes towards MCP-1, a potent chemoattractant of macrophages, should be measured.

D is correct. Figure 2 shows that CA macrophages are less motile than AA macrophages. In order to conclude that this distinction is due to chemoattractant in the neuron- and astrocyte-conditioned media, the researchers must show that the difference in migration is NOT caused by variation in intrinsic migratory capability. To control for this capability, they could determine the relative number of macrophages of each type that migrate toward a known chemoattractant of macrophages. A: As stated above, we need to rule out the possibility that AA cells are simply better at migrating than CA cells. B: It is not necessary to isolate the chemoattractant in each of the conditioned media in order to conclude that chemotaxis is caused by one of them. This might be helpful information for a follow-up experiment, but would not serve as a control. C: This experiment will tell the researchers whether the chemoattractant was a protein or a smaller molecule, but it would not rule out chemotaxis being affected by intrinsic differences in migration between CA and AA macrophages.

A psychosis arising from an advanced stage of syphilis, in which the disease attacks brain cells, is called: A. Korsakoff's syndrome. B. delirium tremens. C. schizotypal personality disorder. D. general paresis.

D is correct. General paresis, also known as general paralysis of the insane or paralytic dementia, is a neuropsychiatric disorder affecting the brain, caused by late-stage syphilis. A: Korsakoff's syndrome is a neurological disorder caused by a lack of thiamine (vitamin B1) in the brain. Its onset is linked to chronic alcohol abuse or severe malnutrition, or both. B: Delirium tremens is an acute episode of delirium that is usually caused by withdrawal from alcohol. C: Schizotypal personality disorder is a personality disorder characterized by a need for social isolation, anxiety in social situations, odd behavior and thinking, and often unconventional beliefs.

The researchers' original hypothesis about the motives Arab IMGs have for adopting American medical culture would be best described as grounded in: A. conflict theory. B. functionalist theory. C. behaviorist theory. D. symbolic interaction theory.

D is correct. Symbolic interaction theory states that people act based on the meanings of cultural symbols that are derived from social interaction. In this case, the hypothesis is that Arab IMGs want to attain the identity of "American doctor," which has certain cultural symbols and norms attached to it. By adding these attributes to their own identity, they will affect their own and others' perceptions and beliefs, causing themselves and native doctors to view the IMG as a legitimate American doctor. A: Conflict theory has to do with disparities of resources between groups like social classes, ethnic groups, and genders, none of which are mentioned in the hypothesis. B: Functionalist theory is concerned with finding out how existing social structures promote social stability. It typically concerns itself with the interaction of macro-level institutions and social structures rather than individuals' beliefs and identities. D is a better fit given the focus on socially defined meaning. C: Behaviorism is related to the theories of B. F. Skinner. It is a school of psychological research that focuses on individual behavior alone, ignoring mental states such as beliefs and identities.

During rat embryogenesis, researchers noticed the development of a fluid-filled cavity in cells that had previously undergone morulation. That cavity was most likely a: A. trophoblast. B. gastrula. C. inner cell mass. D. blastocoel.

D is correct. The question is asking us to identify the developmental stage after the morula (a mass of 16 undifferentiated cells). A good way to remember the development of the zygote is the mnemonic "More blasting gas, I'm nervous," which outlines the process of morula to blastula to gastrula to neurulation. The blastocoel is a fluid-filled central region present in the blastocyst during mammalian embryogenesis. The blastocyst consists of an inner cell mass (ICM), along with an outer cell layer called the trophoblast, which surrounds both the ICM and blastocoel. These structures are depicted below. A: The trophoblast is the outer layer of the blastocyst. B: Gastrulation is the stage in embryonic development in which the single-layered blastula becomes the three-layered gastrula, the three germ layers of which are the ectoderm, endoderm, and mesoderm. C: The inner cell mass is the mass of cells within the blastocyst that will eventually give rise to the fetus.

In red blood cells, bicarbonate can be exchanged for chloride in the plasma. Why do red blood cells in venous circulation have a higher concentration of chloride ions? A. Lower concentrations of CO2 in the venous plasma produce bicarbonate and drive the exchange of Cl- from the plasma into the cell. B. Lower concentrations of CO2 in venous erythrocytes produce bicarbonate and drive the exchange of Cl- from the cell into the plasma. C. Higher concentrations of CO2 in venous plasma produce bicarbonate and drive the exchange of Cl- from the cell into the plasma. D. Higher concentrations of CO2 in venous erythrocytes produce bicarbonate and drive the exchange of Cl- from the plasma into the cell.

D is correct. The question stem tells us that erythrocytes can exchange chloride from the plasma with bicarbonate anions. When more bicarbonate is available, there should thus be a higher concentration of chloride ions in the cells. Since an increase in CO2 corresponds to an increase in bicarbonate concentration in erythrocytes, more chloride should enter the cells to take its place. A, B: Venous blood has a relatively high concentration of CO2. C: Most CO2 is not found in the plasma. Additionally, chloride is exchanged from the plasma into the cell, not the other way around.

A particular type of bird makes its home inside the saguaro cactus by burrowing a hole in the side of the cactus. Such holes do not harm the cactus, although the cactus derives no benefit from the presence of the birds. This is an example of which of the following? A. Parasitism B. Competition C. Mutualism D. Commensalism

D is correct. This question asks us to understand the difference between different types of relationships that exist between species. When one species benefits but the other species is neither helped nor harmed, that is commensalism. That best characterizes the relationship in the question. A: Parasitism benefits one species at the cost of harm to another. B: Competition is when two species compete for access to a limited resource. C: Mutualism requires that both species benefit.

Upon reading the results of the study, a student concludes that cytokine Z must act as an anti-inflammatory signaling molecule on cardiac and vascular tissue. The results described in the passage: A. are sufficient to prove his conclusion; subjects in group D had the lowest relative incidence of heart disease. B. are insufficient to prove his conclusion; the relative increase in [Z pre-mRNA] is similar in all groups. C. are sufficient to prove his conclusion; the sample size of the study increases its statistical power. D. are insufficient to prove his conclusion; a mediating variable may be responsible for the observed correlation.

D is correct. This question asks you to critique the student's conclusion based on the information presented in the passage. The student concludes that Z must directly cause the association between plasma [Z] and heart disease. He essentially labels a correlation between the two variables as a causal relationship, which is a sin! Correlation is not necessarily causation. On this basis, you can eliminate choices A and C. Answer choice B is accurate in that the student's conclusion is not sufficiently supported by the results, but the relative increase in [Z pre-mRNA] is not the reason why. Choice D is correct because it points out the possibility that a third variable is responsible for the correlation between heart disease and Z levels. A, C: Again, the relationship between plasma [Z] and heart disease is not necessarily causal. It is possible that another variable is entirely responsible for the heart disease findings, and that [Z] only happens to correlate with that variable. B: The fact that the relative increase in [Z pre-mRNA] is similar across all groups is irrelevant to the fact that we cannot determine whether a causal relationship exists here.

Which of the following theories would provide the best support to the idea that mirror neurons are involved in language acquisition? A. Chomsky's language acquisition theory B. Freud's drive theory C. Skinner's operant conditioning theory D. Vygotsky's social learning theory

D is correct. Vygotsky's social learning theory heavily stresses the role of people and interactions in language acquisition, which would involve mirror neurons. A: According to Chomsky's view, individuals have an innate language acquisition device. B: Drive theory contends that development is motivated by innate drives. C: Operant conditioning contends that behavior is motivated by contingencies.

Which of the following best explains the failure of doxycycline to inhibit human protein synthesis? A. Eukaryotes do not have ribosomes. B. Eukaryotic transcription occurs in the nucleus, which protects it from doxycycline. C. Eukaryotes have lysosomes, which degrade the drug. D. Eukaryotic ribosomes lack a binding site for the drug.

D is correct. We are told in paragraph 2 that doxycycline works via targeting the 30S ribosomal subunit. Eukaryotic ribosomes are larger and contain more rRNA than their prokaryotic cousins. Prokaryotes have 70S ribosomes, with a 50S and a 30S subunit, whereas eukaryotes have 80S ribosomes, with 60S and 40S subunits. As a result, the aminoacyl-tRNA binding site in eukaryotes is different enough that doxycycline cannot interfere with it. Prokaryotic vs. eukaryotic ribosome structure is depicted below. A: All cells have ribosomes. This answer is just flat-out wrong. B: Doxycycline targets translation, not transcription. While transcription does occur in the nucleus, translation occurs at ribosomes which we are told is the target of the drug. C: Although eukaryotic cells have lysosomes and prokaryotic cells do not, the lysosome does not usually participate in drug metabolism. If the drug was degraded by lysosomes, then it would not be a very good antibiotic against endosymbiotic organisms like Wolbachia.

Empathy Altruism

Empathy altruism is the idea that you are more likely to help people towards whom you feel empathy.

Absolute vs relative refractory period

First, we need to understand the difference between the absolute and relative refractory periods. The absolute refractory period lasts nearly the entire duration of an action potential, during which time a second action potential cannot be generated. During this time, voltage-gated sodium channels are "inactivated." If this term is not familiar, note that voltage-gated sodium channels have two gates that must be open for sodium to flow inward and depolarize the cell membrane. If the "inactivation gate" is closed, the channels are inactivated. If the inactivation gate is open but the activation gate is closed, the channel is "de-inactivated" — it isn't inactivated, but it is not yet open either. This "de-inactivation" occurs once the action potential nears its end and the membrane voltage becomes sufficiently low (generally during the hyperpolarization phase). At this time, the inactivation gate opens and the activation gate closes. Since the channel is not inactivated, a stimulus could theoretically produce an action potential, but since the cell is hyperpolarized, this stimulus would need to be larger than normal. This interval is termed the relative refractory period, which is what this question asks about. At this time, again, sodium channels are de-inactivated; potassium channels are still activated, allowing potassium to continue flowing out of the cell to finish the action potential. Absolute: Na+ inactivation gate closes, activation gate still open Relative: Na+ inactivation gate reopens and activation gatecloses [de-inactivation] - ready to participate in AP again During the relative refractory period, a stronger than normal stimulus is needed to elicit neuronal excitation. After the absolute refractory period, Na+ channels begin to recover from inactivation and if strong enough stimuli are given to the neuron, it may respond again by generating action potentials.

Which of the following patients will be expected to show the symptoms of mitochondrial myopathy? A. A man whose paternal grandmother had the disorder B. A woman whose paternal grandmother had the disorder C. A man whose son has the disorder D. A woman whose son has the disorder

Focus on the fact that A and B are essentially the same ambigous statement whereby there is too much we don't know. It's possible, but unlikely, especially because it's a rare disorder. D is correct. In fact, any one of the individuals described could have the disease, but which of them will be expected to have it? Remember, mitochondrial myopathy is always passed down through the maternal line. Thus, choice D must be correct. A woman whose son has the disorder would have to have given it to him herself, since he inherited her mitochondria. A, B: If one's paternal grandmother carries the faulty mitochondria, she will pass them on to all of her children, including sons. Her son, however, will not pass the disorder on. Unless the woman he has children with coincidentally has the disorder as well (and it's a rare disorder), there is no reason for the children of this man to have it, whether male or female. C: Since men do not pass their mitochondria down to offspring, the son of this man must have inherited the disease from his mother. While the father (the man in question) may have mitochondrial myopathy, we have no way of knowing for certain, and it is unlikely due to the rarity of the condition.

Based on the passage, CR-3 is most likely to be: A. an immunoglobulin. B. an antigen receptor. C. a transcription factor. D. a receptor tyrosine kinase.

HOLY SHIT BE CAREFUL AND DON'T JUST JUMP TO CONCLUSIONS WITHOUT PROOF. SOMETIMES IT IS THAT SIMPLY BUT OTHERS IT ISN'T. B is correct. The passage states that CA macrophage phagocytosis can be inhibited by blocking CR-3. Since this inhibition involves antibodies, we know that CR-3 must "live" in the membrane and face the exterior, meaning that it is likely to be some kind of receptor. Phagocytosis in macrophages occurs after the macrophage has identified its target via antigen receptors. Without an antigen receptor, the macrophage is effectively blind to pathogens (or, in this case, myelin). A: This is tempting, but the final paragraph states that the phagocytosis was inhibited by anti-CR3 antibodies (immunoglobulins), not that CR3 is an antibody itself. Note that macrophages do not produce antibodies. C: Phagocytosis is not under the control of a single transcription factor. D: Receptor tyrosine kinases are commonly found as hormone receptors; they do not play a direct role in macrophage phagocytosis.

Integrin's role in adhesion

Integrins are transmembrane receptors that modulate cell-to-extracellular matrix interactions. Specifically, these proteins often attach the cell to collagen and fibronectin fibers.

Interaction variable

Interaction variables have effects that, when combined with the effects of other variables, are not additive. In other words, two variables may impact the dependent variable much more when presented together than one would expect if the effects of each variable alone were added.

According to the passage, what total length of DNA is found in the average human cell before it is condensed for mitosis? A. 0.3 m B. 0.9 m C. 1.8 m D. 2.6 m

Key here was to realize that the nuclear material would be duplicated. So there are 6 billion nucleotides (3 billion on each strand) but there are 6 billion basepairs upon being replicated. Each base pair then has 0.3 nm length. C is correct. This question asks us to determine the total length of the nuclear material in a cell. Prior to being condensed, the DNA will be duplicated, giving us ~6 billion base pairs (bp) of DNA. If each one has a length of 0.3 nm (paragraph 3), this gives: (6 x 109 bp)(0.3 x 10-9 m/bp) = 1.8 m. A: This answer may result from confusion between the average length of one nucleotide (0.3 nm) and what the question is asking for, which is the total length of DNA found in an average human cell. B: This is the total length of DNA found in an average haploid human cell. Human cells are diploid prior to the time when DNA is condensed. D: This answer results from miscalculation.

kin selection theory

Kin selection is a concept from evolutionary psychology and sociology, in which people will help their relatives even when it is costly to them.

Kinesthetic Sense

Kinesthetic sense refers to our ability to sense linear and rotational acceleration. The organ responsible for this is the ear, which is divided into three major parts: the outer, middle, and inner ear. The inner ear contains the cochlea, which is crucial for hearing, and the vestibule and the semicircular canals, which account for linear and rotational acceleration, respectively. The kinesthetic sense is also linked to proprioception, which occurs due to receptors found mostly in the muscles and joints. Proprioception allows us to perceive where our bodies are in space. For example, even with your eyes and ears covered, you can know where your foot is in space.

Following puberty, the testes begin producing large amounts of testosterone. After production, the testosterone: A. is stored in secretory granules until needed to be secreted in response to declining plasma testosterone concentrations. B. diffuses into the circulatory system and is transported around the body while bound to a plasma protein. C. is sequestered in the nucleus, where it upregulates genes associated with secondary sex characteristics in males. D. is transported to target tissues, where it binds to cell surface receptors and triggers a second messenger cascade.

SHOULD HAVE BEEN ABLE TO RATIONALIZE THIS ONE. B is correct. Remember that testosterone (shown below) is a steroid hormone. As such, it can freely diffuse through cell membranes. Also, as a hormone, testosterone is transported throughout the body in the circulatory system, not confined to the nuclei of the testes. Testosterone must bind to a transport protein since it is not hydrophilic and thus cannot simply dissolve in the blood plasma directly. A, D: Both of these characteristics describe peptide hormones. Also, choice A is incorrect because testosterone (like any steroid hormone) could just diffuse through the membranes of vesicles. C: As a steroid, testosterone can't be sequestered in any membrane-bound organelle.

Which of the following best describes how a shift to the right in the dissociation curve in Figure 1 results in more oxygen delivered to tissue? A. The distance between the curves at 100 mmHg is less than the distance between the curves at 40 mmHg. B. The distance between the curves at 100 mmHg is more than the distance between the curves at 40 mmHg. C. On the right-shifted curve, hemoglobin will pick up significantly more oxygen in the lungs. D. On the right-shifted curve, hemoglobin will pick up significantly less oxygen in the lungs.

SHOULD HAVE GOTTEN THIS ONE RIGHT IF YOU USED GOOD POE SKILLS. A is correct. When the curve is shifted to the right, the oxygen affinity of hemoglobin at high partial pressures is less affected than it is at lower pressures. We can see this by looking at Figure 1. At a PO2 of 100 mmHg, the difference in saturation between a normal and right-shifted curve is minimal. However, at a PO2 of 40 mmHg, the difference is more profound. As a result, the amount of oxygen that each red blood cell picks up in the alveoli of the lungs is not significantly decreased, but the amount of oxygen release in the tissues increases markedly. The difference in distance between the curves at 40 mmHg and 100 mmHg is shown below. B: This is not a true statement; the distance between curves at 100 mmHg is less than the distance between curves at 40 mmHg. C: Again, this is untrue. The oxygen affinity is still slightly decreased on a right-shifted curve, even at a high PO2. D: Even if this statement were true, it would not explain how a rightward shift could result in more oxygen being delivered to the tissue.

Sleep Stuff

Scientists can monitor the electrical activity of the brain during sleep. Sleep is divided into four stages, each with its own associated electrical, psychological, and physical manifestations. The brain waves of a fully-awake person oscillate between a high-frequency, low-amplitude pattern (beta waves) and higher-amplitude, high-frequency, faster patterns (alpha waves), depending on the state of alertness. Alpha waves are more consistent (synchronous) than beta waves. When a person falls asleep, they enter the first of the four stages of sleep. Stage 1 sleep primarily shows theta waves (low amplitude, irregular frequency). In this stage, rolling movement of the eyes occurs with moderate skeletal muscle activity. In Stage 2 sleep, theta waves continue, but are now interspersed with K-complexes (single high-amplitude, low-frequency waves) and sleep spindles (bursts of multiple high-frequency, moderate-amplitude waves). During this stage, there is no eye movement, but skeletal muscle activity remains at a similar level as Stage 1. During Stage 2, heart rate, temperature, and respiration rate decrease. Stage 3 sleep marks the transition into slow-wave sleep, which includes both Stage 3 and Stage 4. In this stage, delta waves (high amplitude, low frequency) predominate. As Stage 3 progresses, higher-frequency waves disappear and Stage 4 sleep begins. During Stage 4, digestion and heart rate slow and growth hormones are released. In the final stage, rapid-eye-movement (REM) sleep occurs. During REM sleep, very little skeletal movement takes place. In fact, during REM sleep, brainwaves, heart rate, and respiration rate are very similar to what is observed when a person is awake. REM is also the stage when a person typically dreams. A sleep cycle is a complete progression through all of the stages of sleep, from Stage 1 to REM and over again. At the beginning of the night, a person spends most time in Stage 4, but as the night progresses, REM predominates, and a person may even have very brief moments of being awake. The length of the sleep cycle increases from childhood to adulthood, from about 50 minutes to 90 minutes, respectively.

A patient is administered a drug which mimics the effects of the antagonist hormone of calcitonin. Which of the following is a likely direct effect of this drug? A. Increased buildup of hydroxyapatite crystals in long bones B. Decreased plasma concentrations of Ca2+ C. Increased metabolic rate D. Increased osteoclast activity

THIS ONE WAS SO EASY! READ CAREFULLY. D is correct. Calcitonin decreases plasma concentrations of Ca2+ by exerting a number of effects. One key example is that calcitonin stimulates bone formation by increasing osteoblast activity and decreasing osteoclast activity. The antagonist hormone to calcitonin is parathyroid hormone (PTH), which acts to increase plasma Ca2+ concentrations by (among other things) decreasing bone formation by osteoblasts and increasing bone degradation by osteoclasts. Thus, a drug which mimics parathyroid hormone would increase osteoclast activity. In typical individuals, calcitonin and PTH act antagonistically to facilitate bone remodeling, or the degradation of older, existing bone and the formation of new bone in its place. A highly simplified schematic of bone remodeling, including the roles of these hormones, is shown below. A, B: These are effects of calcitonin, which reduces plasma Ca2+ levels by increasing the rate of bone formation. However, the question does not ask about calcitonin; it asks about the antagonist hormone to calcitonin, which would promote the opposite effects. C: Metabolic rate is regulated by thyroid hormone, not calcitonin or parathyroid hormone.

Even if something is true it doesn't mean what?

That it's "correct" in the sense that it doesnt necessarily answer the question. Make sure it answers the question

Inactivated state WRT Na+ channels

The channels gate will not open regardless of the membrane potential

If a trait skips generations and there are equal numbers of affected girls and boys then?

The trait follows an autosomal recessive pattern of inheritance.

Universal Emotions

These include: anger disgust fear surprise happiness sadness contempt.

endosymbiotic

a smaller organism that lives within another organism, the theory of how eukaryotic cells were formed. If this word is used then it means that something is living within something else.