AAMC/Bio
A lower-than-normal blood pressure will cause which of the following effects on the rate of plasma clearance of Substance A? An increase, because the concentration of Substance A in the urine will increase An increase, because the ADH levels will be very low A decrease, because the decreased rate of urine output will allow more reabsorption by the kidney A decrease, because ADH levels will be very high
A decrease, because the decreased rate of urine output will allow more reabsorption by the kidney you know for sure you will have a decrease in urine because glomerulus will not be functioning as well due to low blood pressure Low blood pressure could have an effect on ADH levels (as suggested in answer choices B and D), which could, in turn, affect the amount of substance A in the urine, but there is not enough information in the passage to decide if such an effect exists and, if it does, whether its effect would overcome the certain affect of lowering the blood pressure. The best answer is answer choice C: that low blood pressure decreases the glomerular filtration rate, allowing more time for reabsorption and decreasing the amount of substance A in the urine. Blood pressure is the source of the energy that forces fluid into the capsular space. If the heart stopped and the blood in the glomerular capillaries had no hydrostatic pressure, fluid in the space around the glomerulus would flow back into the capillary bloodstream. This would occur because the protein-rich blood would be hypertonic with respect to the protein-poor fluid in the capsular space so that the fluid would flow down the osmotic gradient into the blood.
Albumin (plasma protein)
An increase in plasma albumin will upset the osmotic balance because the blood will become hypertonic with respect to the tissue. Water will have to flow into the bloodstream to reestablish equilibrium. One of the causes of edema, increased fluid in body tissues, is a decrease in the plasma protein level. This occurs, for instance, in starvation when the body is forced to use its albumin as an energy source. An increase in the plasma protein level would have the opposite effect: fluid would enter the bloodstream (answer D). The most abundant plasma protein; synthesized in the liver and provides colloid osmotic pressure which attracts tissue fluid into blood plasma; helps maintain normal blood volume and pressure.
endoderm
GI tract epithelium (liver, pancreas, etc.) respiratory epithelium lining of lungs urinary bladder
In mammals, which of the following events occurs during mitosis but does NOT occur during meiosis I? Synapsis The splitting of centromeres The pairing of homologous chromosomes The breaking down of the nuclear membrane
One of the key differences between mitosis and meiosis occurs during their respective anaphases. During anaphase of mitosis, sister chromatids are pulled apart at the centromeres, each becoming an independent chromosome in the two diploid daughter cells. During anaphase I of meiosis I, homologous pairs of chromosomes are separated into the two daughter cells. However, each chromosome still consists of two sister chromatids joined to each other at the centromere. It is not until anaphase II of meiosis II that the centromere is split and the sister chromatids separate. Thus, B is the best answer. Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis.
heart, uterus, veins and arteries, small intestines
Skeletal and cardiac muscles contain striated muscle fibers. Smooth muscles do not. Of the options listed, only A, the heart, is made of cardiac muscle and therefore has striated muscle fibers. The primary muscle type of the uterus (B), arteries and veins (C), and the small intestine (D) is smooth muscle. Thus, A is the best answer.
Capillaries in the kidney and elsewhere in the body maintain fluid homeostasis by balancing hydrostatic and osmotic pressures. Which of the following is the initial effect of a blood clot forming on the venous side of a capillary bed? Net fluid flow in the direction of interstitial spaces will increase. Net fluid flow in the direction of interstitial spaces will decrease. Capillary osmotic pressure will increase. Capillary osmotic pressure will decrease.
Solution: The correct answer is A. After introducing the idea of fluid homeostasis, which is obtained by balancing hydrostatic and osmotic pressures, the question asks the examinee to predict the consequences of a blood clot on the venous side of a capillary bed. To answer this, it is necessary to know that blood flows from arteries to capillaries and then to veins. If flow is blocked at the venous side, blood would accumulate in the capillaries. Thus, hydrostatic pressure would build up in the capillaries, causing a net increase in fluid flow into the interstitial spaces. A is therefore correct. B is incorrect because there will be an increase in net fluid flow into the interstitial spaces, not a decrease. C is not the best answer because the increase in osmotic pressure in the capillaries would be an indirect result of the fluid flow out of the capillaries. D is incorrect because the flow of fluid out of the capillaries would slightly increase, not decrease, the osmotic pressure. Thus, A is the best answer.
Dewlaps that reflect UV light would evolve by natural selection only if: individuals with UV-reflective dewlaps produced more offspring than did individuals without them. individuals with UV-reflective dewlaps were better able to communicate than individuals without them. individuals with UV-reflective dewlaps were less subject to predation than individuals without them. individuals with UV-reflective dewlaps mated more frequently than did individuals without them.
Solution: The correct answer is A. Although many different types of adaptations may help an individual organism survive, they will not be passed on to the next generation unless the organism produces offspring, passing on the genes that cause the advantageous phenotype. To evolve by natural selection and become a general characteristic of the species, the genes that cause dewlaps to reflect UV light must become a significant portion of the gene pool, which will most likely occur if individuals with UV-reflective dewlaps produce more offspring than do individuals without them. Thus, A is the best answer.
The discovery that the amount of thymine equals that of adenine and the amount of guanine equals that of cytosine in a given cell provides supporting evidence that: the Watson and Crick model of DNA is correct. DNA is the genetic material. the genetic code is universal. the code for one amino acid must be a triplet of bases.
Solution: The correct answer is A. In the Watson and Crick model of DNA structure, the nitrogenous bases form hydrogen bonds with each other in a 1:1 ratio: guanine pairs with cytosine, and adenine pairs with thymine. This implies that the amount of guanine and cytosine would be the same, and the amount of adenine and thymine would be the same. Thus, A is the best answer.
The confining membrane shown in Figure 1 is most similar structurally to a: eukaryotic cell membrane. prokaryotic cell wall. bacterial spore coat. bacterial capsule.
Solution: The correct answer is A. Many viruses form infective particles (virions) by budding off the surface of eukaryotic cells and becoming enclosed in a vesicle composed of the host's cell membrane. Such eukaryotic cell membrane is made up of a bilayer of amphipathic lipids with associated proteins. The diagram shows such a membrane, so the answer must be A. Most bacterial cells (prokaryotes) have an additional, thicker carbohydrate wall. Cell walls (choice B), spore coats (choice C) and capsules (choice D) do not have the lipid bilayer structure shown.
Contraction of the diaphragm results in a: more negative IPP and inspiration. more negative IPP and expiration. more positive IPP and inspiration. more positive IPP and expiration.
Solution: The correct answer is A. The diaphragm is a muscular partition between the abdominal and thoracic cavities. It is dome-shaped at rest curving up toward the lungs and heart. It flattens when it contracts during inspiration. Because it is anchored around its edges to the ribs and spine, when the diaphragm contracts the volume of the thoracic cavity increases. This decreases the pressure (IPP) in the pleural cavity between the thoracic wall and the lung. Fresh air flows in to equalize the pressure inflating the lung.
If blood pressure doubled and the resistance to blood flow increased by 50%, the amount of blood pumped by the heart would have: increased by 1/3. increased by 1/2. decreased by 1/3. decreased by 1/2.
Solution: The correct answer is A. The passage states that P = CO × VR. Solving the equation for cardiac output (CO) and letting the original CO equal P/VR the new CO would then equal 2P/(3/2)VR. Reducing this equation shows that the new CO is 4/3 the old CO, or an increase of 1/3. Thus, A is the best answer. **Remember: increase of 50% is 1.5 or 3/2
Most bacterial cells and human cells are alike in: the ability to produce ATP via ATP synthase. the chemical composition of their ribosomes. their enclosure within cell walls. the shape of the self-replicating structures that carry their DNA.
Solution: The correct answer is A. The question asks the examinee to identify a characteristic common to most bacterial and human cells. Of the options listed, only A, the ability to produce ATP via ATP synthase is common to both bacterial and human cells. Both types of cells possess a membrane-embedded electron transport chain capable of generating a H+ gradient, which drives synthesis of ATP via ATP synthase. This ATP synthesis takes place on the plasma membrane of bacteria and on the inner mitochondrial membrane in human cells. The chemical composition of prokaryotic and eukaryotic ribosomes (B), although similar, is distinct enough that several types of antibiotics are able to preferentially target prokaryotic ribosomes over eukaryotic ribosomes. Of human and bacterial cells, only bacterial cells have cell walls (C), and most bacterial chromosomes are circular whereas human chromosomes are linear (D). Thus, A is the best answer.
One characteristic common to arteries, veins, and capillaries is the: presence of a layer of endothelial cells. presence of numerous valves that prevent the backflow of blood. ability to actively dilate or constrict in regulating blood flow. ability to supply surrounding tissues with nutrients by filtration and diffusion.
Solution: The correct answer is A. The question asks the examinee to identify one characteristic common to arteries, capillaries, and veins. A is correct because all three types of vessels possess an inner layer of endothelial cells. B is incorrect because only veins have valves. C is incorrect because only certain types of arteries dilate or constrict to regulate blood flow. D is incorrect because the exchange of nutrients with the surrounding tissues occurs only in capillaries. Thus, A is the best answer.
Hemophilia, a disease in which the time required for blood to clot is greatly prolonged, is determined by a sex-linked gene. Suppose a man with normal blood clotting marries a woman with normal blood clotting whose father was a hemophiliac. If this couple has three sons, what is the probability that hemophilia will be transmitted to all three of them? 1/8 1/4 3/8 1/2
Solution: The correct answer is A. The woman inherited one X chromosome from her father and one from her mother. The father only had one X chromosome to contribute and that X chromosome contained the hemophilia gene. The mother will pass on one X chromosome to her sons, either the X chromosome containing the normal (wild type) gene, or the X chromosome containing the hemophilia gene. The probability of a son receiving the hemophilia gene and being a hemophiliac is 1/2, because there is a 50-50 chance that this son received an X chromosome carrying the defective gene from his carrier mother. The cumulative probability of all three sons inheriting the hemophilia gene would be the product of the individual probabilities, or 1/2 × 1/2 × 1/2. Thus, answer choice A, 1/8, is the answer.
Kidney failure during severe dehydration is most likely due to: inadequate blood volume for effective filtration. inability to produce sufficient urine. buildup of salts in the distal tubules. increased body temperature.
Solution: The correct answer is A. This question asks the examinee to identify the cause of kidney failure during times of extreme dehydration. As the passage states, severe dehydration greatly reduces the volume of filtrate moving through the nephrons of the kidney. If fluid volume is too drastically reduced, the kidney will be unable to effectively do its job of filtering and maintaining homeostasis within bodily fluids. Thus, A is the best answer.
The chemical valinomycin inserts into membranes and causes the movement of K+ into the mitochondria. Based on Figure 1, if mitochondria are treated with valinomycin, the rate of ATP synthesis in the mitochondria will most likely: decrease, because the K+ will compete with protons at the active site on ATP synthetase. decrease, because movement of K+ into the mitochondrial compartments will disrupt proton movement into the intermembrane space. increase, because the net positive charge in the mitochondria will cause increased movement of protons into the intermembrane space. increase, because the additional positive charge will further activate ATP synthetase.
Solution: The correct answer is B. Any disruption of mitochondria is likely to decrease ATP production since they are a major cellular source of that molecule. Answer choices C and D can not be right because they propose an increase in ATP production. There is no information in the question to suggest that valinomycin will cause K+ to compete with H+ for an active site on ATP synthetase. Furthermore, one would suspect that ATP or precursor molecules such as phosphate and ADP would occupy the active site on the ATP synthase molecule. Answer choice A, therefore, does not seem plausible. The question does provide the information that valinomycin increases the flow of K+ across the membrane. An influx of another positively charged ion into the compartment would disrupt the electrochemical gradient responsible for the necessary flow of protons. Answer B, therefore, seems more plausible than any other choice.
An ulcer that penetrated the wall of the intestine would allow the contents of the gastrointestinal tract to enter: the perineum. the peritoneal cavity. the pleural cavity. the lumen of the intestine.
Solution: The correct answer is B. If an ulcer penetrated the walls of the intestine, this would allow the contents of the gastrointestinal tract to enter the peritoneal cavity. Membranes surround this cavity, which would prevent further transport of the gastrointestinal contents through the rest of the body. An ulcer in the small intestine would not allow the contents to enter the lumen because this is the normal place in which the contents are found.
The sequence of events in the human menstrual cycle involves close interaction among which organs? Hypothalamus-thyroid-ovary Hypothalamus-pituitary-ovary Pituitary-thyroid-ovary Pituitary-adrenal glands-ovary
Solution: The correct answer is B. Neither the thyroid gland nor the adrenal glands are particularly involved in the menstrual cycle. The hypothalamus exerts control over the pituitary hormones involved in menstruation by secreting hormone-releasing factors into the pituitary portal circulation. The gonadotropic hormones FSH and LH produced by the pituitary and the ovarian hormones estrogen and progesterone all have a role in regulating the human menstrual cycle. Therefore, close interaction among the hypothalamus, the pituitary, and the ovary is necessary for the human menstrual cycle. Thus, answer choice B is the best answer.
Colchicine most likely relieves gout symptoms through what mechanism? Prevention of uric acid diffusion through cell membranes Inhibition of leukocyte phagocytosis of uric acid crystals Inhibition of uric acid crystal formation Maintenance of the pH optimum for PRPP synthetase
Solution: The correct answer is B. Phagocytosis requires that the cell change shape dramatically as it surrounds and engulfs large extracellular particles. Microtubules are one of the cytoskeletal elements that help determine cell shape. This function relies on the ability of the microtubules to disassemble and reorganize. The drug colchicine inhibits microtubule reorganization and would therefore inhibit phagocytosis of uric acid crystals by leukocytes. Thus, B is the best answer.
What is the net volume of fresh air that enters the alveoli each minute, assuming that the breathing rate is 10 breaths/min, the tidal volume is 800 mL/breath, and the nonalveolar respiratory system volume (dead space) is 150 mL? 65 mL 95 mL 6500 mL 7850 mL
Solution: The correct answer is C. The amount of air entering the lungs in a single breath, or tidal volume, is given as 800 mL/breath. Of that 800 mL only 650 mL reaches the alveoli per breath (800 mL of air inhaled minus 150 mL of nonalveolar respiratory volume). Therefore the net volume of air that reaches the alveoli each minute is equal to 650 mL/breath multiplied by 10 breaths/min, or 6500 mL. Thus, C is the best answer.
The autonomic nerve fibers that directly innervate the heart to cause cardiac slowing are: sympathetic motor fibers. sympathetic sensory fibers. parasympathetic motor fibers. parasympathetic sensory fibers.
Solution: The correct answer is C. The autonomic nerve fibers that innervate the heart to slow it are the parasympathetic motor fibers of the vagus nerve. Sympathetic motor fibers increase heart rate. Sensory fibers carry information from the heart to the central nervous system. Thus, answer choice C is the best answer.
The validity of the Regulative Hypothesis could best be demonstrated in an organism by showing that: incomplete embryos develop from separated cells. cell fate is dependent on factors within the cell. transplanted embryonic cells show position-dependent development. genes determining cell development are distributed asymmetrically.
Solution: The correct answer is C. The development of incomplete embryos, described in choice A, falsifies the Regulative Hypothesis. Answer choice B states that the fate of a cell depends on its own internal factors, but this would be true whether the Mosaic Hypothesis or the Regulative Hypothesis was true. Cells must have genes to guide their fate. The question is whether they have a full complement of the organism's genes or just a part. Answer choice D restates the Mosaic Hypothesis, that genes are distributed unevenly to daughter cells during development. Answer choice C, the correct answer, however, supports the Regulative Hypothesis. If all cells contain identical information for construction of the organism, then some external factor must tell different parts what they should become. If specific courses of development were shown to be dependent on the position of the cell in the embryo, it would explain this aspect of the Regulative Hypothesis. By supplying an answer to the question of how the parts of an animal develop differently when they have the same genes, that information buttresses the Regulative Hypothesis. Thus, answer choice C is the best answer.
In comparison with the wall of the right ventricle of the heart, the left ventricular wall is: thinner and generates a higher pressure when it contracts. thinner and generates a lower pressure when it contracts. thicker and generates a higher pressure when it contracts. thicker and generates a lower pressure when it contracts.
Solution: The correct answer is C. The difference in size between the thin wall of the right ventricle and the thick wall of the left ventricle is dramatic when viewed in cross section. The peak pressure in the left ventricle is 120 mmHg while the peak pressure in the right ventricle is only 25 mmHg. The right ventricle pumps blood through the lungs. The left ventricle pumps blood through the entire rest of the body. The difference in the size of the lung compared to the rest of the body suggests that the left ventricle develops more pressure and has a thicker wall than the right. The organs through which the left ventricle pumps blood are farther away from the heart than the lungs and resistance in a tube is inversely proportional to the length of the tube. This would also suggest a thicker wall for the left ventricle and greater pressure. The correct answer is choice C, that the left ventricle has a thicker wall and develops more pressure than the right.
A man is treated with low doses of an estrogen analogue to destroy an estrogen-responsive adrenal tumor. Compared to an age-matched control (no estrogen treatment), this patient's chances of developing osteoporosis will most likely be: increased. decreased. approximately the same. approximately the same, but the disease will appear at an earlier age.
Solution: The correct answer is C. The passage only states that post-menopausal women show the accelerated bone loss and the acceleration slows after eight to ten years. From this it seems likely that the acceleration has something to do with withdrawal of estrogen. Administration of estrogen to men would then have no therapeutic effect on bone loss, since they should not be suffering from withdrawal of the hormone, having never had high levels. Men given estrogen should have the same chance of developing osteoporosis as a control population, answer choice C.
According to the passage, superantigens increase the number of activated T cells over activation levels observed with conventional antigens by a factor of: 20. 5,000. 20,000. 100,000.
Solution: The correct answer is C. The passage states that 20 percent of T lymphocytes are activated by superantigens, while one in 100,000 is activated by conventional antigens. Taking 20 percent of 100,000 yields 20,000, so the correct response is answer choice C.
It is now generally accepted that H. pylori can cause ulcers. Proof of this most likely depended on the demonstration that: people with stomach ulcers have antibodies to H. pylori. healthy individuals have antibodies to H. pylori. ulcers could be produced in healthy organisms by infecting them with H. pylori. the organism can be passed from mother to fetus during pregnancy.
Solution: The correct answer is C. The question asks the examinee to identify a key criterion that an organism must meet before it can be declared the infectious agent responsible for causing a particular disease or condition. One of these criteria is the demonstration that the putative infectious agent is capable of causing the disease or condition in an organism that was healthy prior to exposure to the agent. C correctly identifies this criterion by stating that proof that H. pylori can cause stomach ulcers depended on demonstrating that ulcers can be produced in healthy organisms by infecting them with H. pylori. Although A, B, and D may or may not be true, they do not demonstrate causality. Thus, C is the best answer.
Which of the following processes is LEAST directly influenced by adrenergic drugs? Peristalsis Secretion of digestive enzymes Enzymatic breakdown of food molecules Nutrient delivery to muscles and organs
Solution: The correct answer is C. The question asks the examinee to identify the bodily process among the options listed that is LEAST directly influenced by adrenergic drugs. According to the passage, adrenergic drugs mimic activation of the sympathetic nervous system; therefore, the best answer will be the process that is LEAST directly controlled by the sympathetic nervous system. The sympathetic nervous system directly inhibits peristalsis (A) and secretion of digestive enzymes (B). It also increases the blood glucose concentration and causes dilation of the blood vessels that supply the deep muscles and internal organs, which aids nutrient delivery (D) to these tissues. The sympathetic nervous system does not directly affect the activity of digestive enzymes (C) after they have been secreted. Thus, C is the best answer.
The amount of NE released by sympathetic nerve terminals will be most strongly influenced by a change in which of the following? Alpha receptor sensitivity Alpha receptor density Extracellular [Ca2+] COMT activity
Solution: The correct answer is C. The question asks the examinee to identify the factor among the options listed that will most strongly influence the amount of NE released by the sympathetic nerve terminal. Of these options, only C, extracellular [Ca+], will influence the amount of NE released by the sympathetic nerve terminal. When an action potential reaches a nerve terminal it triggers the opening of Ca+ channels in the neuronal membrane. Because the extracellular concentration of Ca+ is greater than the intracellular Ca+ concentration, Ca+ flows into the nerve terminal. This triggers a series of events that cause the vesicles containing NE to fuse with the plasma membrane and release NE into the synapse. Thus, C is the best answer.
If restriction of blood flow to the kidneys (by placing clamps on the renal arteries) resulted in an immediate but small increase in blood pressure, followed by the gradual development of severe hypertension, which hypothesis would these results best support? Hypothesis A, because the clamps increased the vascular resistance to blood flow Hypothesis A, because the clamps caused the kidneys to receive less blood Hypothesis B, because the kidneys were responding to decreased glomerular blood pressure Hypothesis B, because the volume of body fluids was probably decreasing
Solution: The correct answer is C. The reduced flow of blood through the renal arteries due to the clamps would cause a decrease in glomerular blood pressure. The kidneys respond to this drop in pressure by activating the renin-angiotensin system of hormones. This increases the amount of sodium and water that is reabsorbed by the kidneys, therefore increasing blood volume and pressure. Thus, C is the best answer.
In addition to the skin and circulatory systems, which of the following organ systems is most likely to be affected by TSS? The musculoskeletal system The digestive system The lymphatic system The respiratory system
Solution: The correct answer is C. The symptoms mentioned in the passage suggest involvement of the circulatory system (hypotension) and skin (rash, desquamation), so the question is asking what other bodily system might be involved in toxic shock syndrome. The other system that is most prominently discussed is the lymphatic system, so choice C must be correct. The other systems are not discussed in the passage and there is no other reason to think they might be involved, so the musculoskeletal system (answer A), digestive system (answer B), and respiratory system (answer D) can be eliminated from consideration.
If these lizards use UV light in communication, a mutation that eliminated UV photoreceptors would probably cause the LEAST disadvantage to: species A. species B. species D. species E.
Solution: The correct answer is D. Assuming that the lizards use the UV-reflectivity of the dewlap primarily as a means of intraspecies communication, species E would most likely be least affected by a mutation that eliminated UV photoreceptors. Its dewlaps are the least UV-reflective of the five lizard species, which indicates that species E is least likely to rely heavily upon this form of communication in the first place. Thus, D is the best answer. remember RIVUXGA
If Anolis lizards have X-Y chromosomal sex determination, the locus of a gene for the UV reflectance pigment: must be on the X chromosome. must be on the Y chromosome. must be on an autosome. could be on a sex chromosome or on an autosome.
Solution: The correct answer is D. Based on the information presented, the gene encoding UV-reflectance pigment could be on a sex chromosome or an autosome. The fact that the pigment is expressed in the dewlap, a structure found only in males, is not sufficient to eliminate any chromosome as the location of this gene. Thus, D is the best answer.
If the dose of Streptococcus Strain A required to cause infection is 1 x 10^5 bacteria and that of Streptococcus Strain B is 5 x 10^4 bacteria, which of the following statements describes the relative potencies of these strains? Strain A is five times as potent as Strain B. Strain A is one-fifth as potent as Strain B. Strain A is twice as potent as Strain B. Strain A is half as potent as Strain B.
Solution: The correct answer is D. Since it takes fewer strain B bacteria to cause an infection than strain A (50,000 versus 100,000, respectively), then strain B is more potent. How much more potent is it? Since 100,000 is twice 50, strain B is twice as potent. Therefore, the correct answer is option D, which states that the strain A is half as potent as strain B. READ THE QUESTION!!!!!!
The pancreas produces which of the following substances for the digestive system? Bile salts Emulsifier Gastric juices Proteolytic enzymes
Solution: The correct answer is D. The pancreas produces several proteolytic enzymes, which are released into the small intestine where they are converted to their active forms of trypsin, chymotrypsin, and carboxypeptidase. Thus, D is the best answer.
Aldosterone stimulates Na+ reabsorption by the kidneys. What changes in blood volume and pressure would be expected as a result of aldosterone deficiency? Increased volume and increased pressure Increased volume and decreased pressure Decreased volume and increased pressure Decreased volume and decreased pressure
Solution: The correct answer is D. The question asks the examinee to determine the result of an aldosterone deficiency on blood volume and blood pressure, given that aldosterone stimulates Na+ reabsorption in the kidney. An aldosterone deficiency would result in lower Na+ reabsorption into the bloodstream. Because H2O passively follows Na+ during reabsorption in the kidney, less Na+ reabsorption would result in less H2O reabsorption into the bloodstream. This would result in decreased blood volume. Blood volume would also be affected by lower blood Na+ levels because there would be less of this ion to osmotically hold water in the extracellular fluid. Decreased blood volume would result in decreased blood pressure as well (D). Thus, D is the best answer.
If DDT accumulates in the liver, all of the following bodily functions may be significantly impaired EXCEPT: absorption of fats in the small intestine. production of bile. detoxification of poisons. regulation of blood pressure.
Solution: The correct answer is D. The question asks the examinee to identify the bodily function that would NOT be significantly impaired by DDT accumulation in the liver. DDT would be expected to affect all liver functions, and, therefore, all options associated with a major liver function are incorrect. The detoxification of poisons and the production of bile, which facilitates fat absorption in the small intestine by breaking large fat droplets into smaller ones, are major liver functions. Therefore, A, B, and C are not correct. The production of factors involved in blood pressure regulation (D) is not a major function of the liver. Thus, D is the best answer. do NOT overthink!!!!!!!
When the environmental temperature is 45° C, which of the following organisms will have the highest body temperature? Human Kangaroo rat Camel Lizard
Solution: The correct answer is D. The question asks the examinee to identify the organism with the highest body temperature in response to elevated external temperatures. This organism will be the organism that is least able to utilize the cooling mechanisms of vasodilation and sweating. A lizard (D) has an impermeable integument, thereby eliminating vasodilation and sweating as options for cooling. Thus, D is the best answer.
Which of the following tissues have cells that are in direct contact with the external environment or elements of the external environment? The lining of the reproductive tract The lining of the respiratory tract The lining of the gastrointestinal tract I and II only I and III only II and III only I, II, and III
Solution: The correct answer is D. The question asks the examinee to identify those tissues that are in direct contact with the external environment or elements of the external environment. Tissues that are exposed to the external environment have mucosal membranes. All of the tissues listed contain an element of mucosa (e.g., the nasal cavity, vagina and anus). Thus, D is the best answer.
Delayed ovulation, as a cause of tubal pregnancy, would most likely be associated with delayed secretion of which of the following hormones? Progesterone Estrogen HCG Luteinizing hormone
Solution: The correct answer is D. The question requires the examinee to identify that luteinizing hormone (D) is the hormone responsible for triggering ovulation. While the sex hormones progesterone (A) and estrogen (B) are either secreted in response to the luteinizing hormone surge or actually trigger the luteinizing hormone surge, respectively, they are not directly involved in triggering ovulation. HCG (C) is the pregnancy hormone, but it doesn't have a role in the typical ovulatory cycle. Thus, D is the best answer. hCG - stimulated by placenta, signals corpus luteum to continue progesterone secretion to maintain endometrium (uterine wall to nourish zygote)
What mechanism could account for this oscillation of cyclin protein concentration?
The graph shown in the question indicates that the concentration of cyclin rises and falls in a regular manner throughout the cell cycle, reaching a peak just at the beginning of mitosis, gradually declining during mitosis, reaching a minimum at the end of mitosis, and gradually increasing during interphase. The mechanism that can best account for this oscillation in the concentration of cyclin is translation of cyclin mRNA (creating the protein from mRNA template) followed by proteolysis (destruction) of cyclin protein during mitosis.
nucleus, ribosome, proteins and related structures
The nitrogenous base, uracil, combined with the sugar ribose and phosphate makes up the nucleotide uridine. It is found in RNA, but not in DNA. The corresponding DNA nucleotide is thymine. Uridine is incorporated into RNA in the nucleus where transcription of DNA into RNA takes place. RNA is manufactured in the nucleus from a DNA template. Therefore, the correct answer is answer choice A. RNA is necessary for protein synthesis by free ribosomes and those attached to endoplasmic reticulum, but it is not synthesized there, so answer choices C and D are incorrect. Proteins are packaged for export in the Golgi apparatus, but it too takes no part in RNA synthesis, so answer choice B is incorrect.
What type or class of chemical messenger traveling in the blood would most probably link the brain with the digestive tract and fat cells in the control of body weight? Neurotransmitters Digestive enzymes Protein receptors Hormones
The question asks the examinee to identify the class of substances that would travel through the bloodstream, linking the brain with the digestive tract. D is the best answer because most hormones travel from the endocrine gland in which they were produced, through the blood, to their target tissue. Neurotransmitters by definition are released at neural synapses, although there are chemicals that act both at synapses and like hormones in the bloodstream. Therefore, A is not the best answer. Digestive enzymes are found in the digestive tract, but they do not travel through the bloodstream. Therefore, B is incorrect. Protein receptors interact with chemical messengers but are not the signal themselves. Therefore, C is not the best answer. Thus, D is the best answer.
muscle contraction
The sliding filament model describes the interaction of actin and myosin during muscle contraction. According to this model, neuronal impulses cause the release of calcium from the sarcoplasmic reticulum within muscle cells. The calcium then binds to troponin, a molecule that along with tropomyosin, blocks the binding sites for myosin on actin molecules. Calcium binding to troponin causes a shift in the troponin/tropomyosin complex, revealing the binding site for myosin. Myosin then binds to actin, causing a conformational change in myosin that "cocks" the head of the myosin molecule and slides the actin filament relative to myosin. ATP binds to myosin, causing it to detach from actin and "recharge" (rebend again). If another binding site is available on actin, myosin will bind again, and slide the actin filament even further. Thus, D is the best answer.
mesoderm
all muscle, bone, and connective tissue Dermis of skin entire cardiovascular and lymphatic system, including blood (circulatory system) urogenital organs (kidneys, ureters, gonads, reproductive ducts)
sensory and motor neurons
can be depolarized with Na+
ectoderm
entire nervous system pituitary gland (both lobes), adrenal medulla cornea and lens inner ear epidermis of skin and derivatives (hair, nails, sweat glands, sensory receptors) Nasal, oral, anal epithelium
nucleic acids and replication processes
https://quizlet.com/109109328/biology-finalchapter-14-flash-cards/
hydrostatic pressure vs. osmotic pressure
https://quizlet.com/19618511/hydrostatic-pressure-vs-osmotic-pressure-flash-cards/
MCAT 3A/B (12.5%): nervous, endocrine, reproductive, muscle, skeletal, skin
https://quizlet.com/249150434/mcat-3ab-125-nervous-endocrine-reproductive-muscle-skeletal-skin-flash-cards/ has other mcat flashcards
MCAT Biochemistry Chapter 1 AA and fatty acids
https://quizlet.com/99473106/mcat-biochemistry-chapter-1-flash-cards/
increased blood pressure will affect the glomerular filtration rate increase flow of fluid through the kidney system and decrease, rather than increase, water reabsorption
increase flow of fluid through the kidney system and decrease, rather than increase, water reabsorption in response to excess ADH being introduced After ADH increases blood pressure, counter measures taken so opposite will happen
Which of the following conclusions regarding virion biology is supported by information given in the passage? Virions lack genetic material. Virions can synthesize proteins. Virions lack enzymes. Virions are obligate parasites.
viruses are obligate parasites Solution: The correct answer is D. One of the characteristics of viruses is that they are obligate intracellular parasites. They are unable to reproduce without the aid of the host cell's metabolic machinery. The passage describes the attempt to grow the particles on "sterilized, noncellular growth media." The failure to grow the unknown agent on such media supports the idea that they are viruses, but does not prove it (many bacteria are also difficult to grow on artificial media). The answer is therefore D that viruses (virions) are obligate parasites. There is no information in the passage to support the idea that the viruses lack genetic material (choice A), no information pertaining to the virion's ability to synthesize enzymes (choice C), and the figure does show a virus containing the enzyme reverse transcriptase (choice D), so those options can be rejected.
