Biology - MCAT Biological and Biochemical Foundations of Living Systems
Card 1 of 11296
The presence of which of the following feature would best indicate a eukaryotic cell?
The presence of which of the following feature would best indicate a eukaryotic cell?
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Organelles are only found in eukaryotic cells which set them apart from prokaryotic cells.
Organelles are only found in eukaryotic cells which set them apart from prokaryotic cells.
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Carbonic anhydrase is a very important enzyme that is utilized by the body. The enzyme catalyzes the following reaction:
A class of drugs that inhibits this enzyme is carbonic anhydrase inhibitors (eg. acetazolamide, brinzolamide, dorzolamide). These drugs are commonly prescribed in patients with glaucoma, hypertension, heart failure, high altitude sickness and for the treatment of basic drugs overdose.
In patients with hypertension, carbonic anhydrase inhibitors will prevent the reabsorption of sodium chloride 
in the proximal tubule of the kidney. When sodium is reabsorbed back into the blood, the molecule creates an electrical force. This electrical force then pulls water along with it into the blood. As more water enters the blood, the blood volume increase. By preventing the reabsorption of sodium, water reabsorption is reduced and the blood pressure decreases.
When mountain climbing, the atmospheric pressure is lowered as the altitude increases. As a result of less oxygen into the lungs, ventilation increases. From the equation above, hyperventilation will result in more 
being expired. Based on Le Chatelier’s principle, the reaction will shift to the left. Since there is more bicarbonate than protons in the body, the blood will become more basic (respiratory alkalosis). To prevent such life threatening result, one would take a carbonic anhydrase inhibitor to prevent the reaction from shifting to the left.
Carbonic anhydrase inhibitors are useful in patients with a drug overdose that is acidic. The lumen of the collecting tubule is nonpolar. Due to the lumen's characteristic, molecules that are also nonpolar and uncharged are able to cross the membrane and re-enter the circulatory system. Since carbonic anhydrase inhibitors alkalize the urine, acidic molecules stay in a charged state.
Which of the following statement(s) will contradict carbonic anhydrase inhibitors' usefulness in patients with hypertension?
Carbonic anhydrase is a very important enzyme that is utilized by the body. The enzyme catalyzes the following reaction:
A class of drugs that inhibits this enzyme is carbonic anhydrase inhibitors (eg. acetazolamide, brinzolamide, dorzolamide). These drugs are commonly prescribed in patients with glaucoma, hypertension, heart failure, high altitude sickness and for the treatment of basic drugs overdose.
In patients with hypertension, carbonic anhydrase inhibitors will prevent the reabsorption of sodium chloride
When mountain climbing, the atmospheric pressure is lowered as the altitude increases. As a result of less oxygen into the lungs, ventilation increases. From the equation above, hyperventilation will result in more
Carbonic anhydrase inhibitors are useful in patients with a drug overdose that is acidic. The lumen of the collecting tubule is nonpolar. Due to the lumen's characteristic, molecules that are also nonpolar and uncharged are able to cross the membrane and re-enter the circulatory system. Since carbonic anhydrase inhibitors alkalize the urine, acidic molecules stay in a charged state.
Which of the following statement(s) will contradict carbonic anhydrase inhibitors' usefulness in patients with hypertension?
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In patients with hypertension, the blood volume is too high resulting in high blood pressure. carbonic anhydrase inhibitors will prevent water absorption by preventing sodium chloride reabsorption. As described from the passage, without sodium reabsorption at the proximal tubule, there will be no electrochemical drive for the reabsorption of water. carbonic anhydrase inhibitors mainly work on the proximal tubule where the majority of water reabsorption occurs.
In patients with hypertension, the blood volume is too high resulting in high blood pressure. carbonic anhydrase inhibitors will prevent water absorption by preventing sodium chloride reabsorption. As described from the passage, without sodium reabsorption at the proximal tubule, there will be no electrochemical drive for the reabsorption of water. carbonic anhydrase inhibitors mainly work on the proximal tubule where the majority of water reabsorption occurs.
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Carbonic anhydrase is a very important enzyme that is utilized by the body. The enzyme catalyzes the following reaction:
A class of drugs that inhibits this enzyme is carbonic anhydrase inhibitors (eg. acetazolamide, brinzolamide, dorzolamide). These drugs are commonly prescribed in patients with glaucoma, hypertension, heart failure, high altitude sickness and for the treatment of basic drugs overdose.
In patients with hypertension, carbonic anhydrase inhibitors will prevent the reabsorption of sodium chloride 
in the proximal tubule of the kidney. When sodium is reabsorbed back into the blood, the molecule creates an electrical force. This electrical force then pulls water along with it into the blood. As more water enters the blood, the blood volume increase. By preventing the reabsorption of sodium, water reabsorption is reduced and the blood pressure decreases.
When mountain climbing, the atmospheric pressure is lowered as the altitude increases. As a result of less oxygen into the lungs, ventilation increases. From the equation above, hyperventilation will result in more being expired. Based on Le Chatelier’s principle, the reaction will shift to the left. Since there is more bicarbonate than protons in the body, the blood will become more basic (respiratory alkalosis). To prevent such life threatening result, one would take a carbonic anhydrase inhibitor to prevent the reaction from shifting to the left.
Carbonic anhydrase inhibitors are useful in patients with a drug overdose that is acidic. The lumen of the collecting tubule is nonpolar. Due to the lumen's characteristic, molecules that are also nonpolar and uncharged are able to cross the membrane and re-enter the circulatory system. Since carbonic anhydrase inhibitors alkalize the urine, acidic molecules stay in a charged state.
Based on the passage, which of the following statements, if true, would contradict the effectiveness of carbonic anhydrase inhibitors as a treatment?
Carbonic anhydrase is a very important enzyme that is utilized by the body. The enzyme catalyzes the following reaction:
A class of drugs that inhibits this enzyme is carbonic anhydrase inhibitors (eg. acetazolamide, brinzolamide, dorzolamide). These drugs are commonly prescribed in patients with glaucoma, hypertension, heart failure, high altitude sickness and for the treatment of basic drugs overdose.
In patients with hypertension, carbonic anhydrase inhibitors will prevent the reabsorption of sodium chloride
When mountain climbing, the atmospheric pressure is lowered as the altitude increases. As a result of less oxygen into the lungs, ventilation increases. From the equation above, hyperventilation will result in more
Carbonic anhydrase inhibitors are useful in patients with a drug overdose that is acidic. The lumen of the collecting tubule is nonpolar. Due to the lumen's characteristic, molecules that are also nonpolar and uncharged are able to cross the membrane and re-enter the circulatory system. Since carbonic anhydrase inhibitors alkalize the urine, acidic molecules stay in a charged state.
Based on the passage, which of the following statements, if true, would contradict the effectiveness of carbonic anhydrase inhibitors as a treatment?
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The proximal tubule has a high permeability for water. In patients with hypertension and/or heart failure, blocking the reabsorption of water at the proximal tubule will lower the blood's volume and blood's pressure. Therefore, if the proximal tubule is impermeable to water, then regulating the site with a carbonic anhydrase inhibitor has no purpose.
The proximal tubule has a high permeability for water. In patients with hypertension and/or heart failure, blocking the reabsorption of water at the proximal tubule will lower the blood's volume and blood's pressure. Therefore, if the proximal tubule is impermeable to water, then regulating the site with a carbonic anhydrase inhibitor has no purpose.
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The process of excretion officially begins after the collecting duct since the collecting duct is the last point of reabsorption.
Urine passes through all of the following structures except the .
The process of excretion officially begins after the collecting duct since the collecting duct is the last point of reabsorption.
Urine passes through all of the following structures except the .
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The path of urine excretion from the body, after filtrate passes through the collecting ducts of the nephrons, begins in the renal pelvis. The renal pelvis collects the concentrated filtrate and transfers it to the bladder via the ureters. During urination, the bladder contracts, and urine exits the body through the urethra.
Vasa recta are capillaries found near nephrons within the kidneys.
The path of urine excretion from the body, after filtrate passes through the collecting ducts of the nephrons, begins in the renal pelvis. The renal pelvis collects the concentrated filtrate and transfers it to the bladder via the ureters. During urination, the bladder contracts, and urine exits the body through the urethra.
Vasa recta are capillaries found near nephrons within the kidneys.
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Which cell type is occasionally called "the fourth germ layer" due to its migratory properties and critical developmental importance?
Which cell type is occasionally called "the fourth germ layer" due to its migratory properties and critical developmental importance?
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The ectoderm is the outer layer of the embryo, which gives rise to the external ectoderm and the neuroectoderm. The neuroectoderm can further be divided into the neural crest and the neural tube. The neural crest migrates from the neural tube early in development. While both external ectoderm and the neural tube form an epithelial layer, the neural crest does not and is actually a highly migratory cell lineage. Furthermore, the neural crest is required for innervation of endodermal organs (forming the enteric nervous system), craniofacial features, innervation of the diaphragm for breathing, and many more critical features. Due to its structural and migratory properties, and its importance in development, the neural crest is often referred to as the "fourth germ layer."
Cardiomyocytes refer to cardiac muscle cells, while hepatocytes are liver cells. Beta cells are found in the pancreas and secrete insulin.
The ectoderm is the outer layer of the embryo, which gives rise to the external ectoderm and the neuroectoderm. The neuroectoderm can further be divided into the neural crest and the neural tube. The neural crest migrates from the neural tube early in development. While both external ectoderm and the neural tube form an epithelial layer, the neural crest does not and is actually a highly migratory cell lineage. Furthermore, the neural crest is required for innervation of endodermal organs (forming the enteric nervous system), craniofacial features, innervation of the diaphragm for breathing, and many more critical features. Due to its structural and migratory properties, and its importance in development, the neural crest is often referred to as the "fourth germ layer."
Cardiomyocytes refer to cardiac muscle cells, while hepatocytes are liver cells. Beta cells are found in the pancreas and secrete insulin.
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In all vertebrates, when the optic cup does not develop in the embryo the lens also does not develop either. This provides evidence for which of the following statements?
In all vertebrates, when the optic cup does not develop in the embryo the lens also does not develop either. This provides evidence for which of the following statements?
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The failure of the lens to form in the absence of the optic cup indicates that the optic cup is necessary for lens development, and may in fact induce it.
This fact says nothing in regards to the timing of neurulation, nor the timing of eye development. Finally, cell differentiation is a gradual process, not all-or-nothing, and the statement is irrelevant to the development of the optic cup and lens.
The failure of the lens to form in the absence of the optic cup indicates that the optic cup is necessary for lens development, and may in fact induce it.
This fact says nothing in regards to the timing of neurulation, nor the timing of eye development. Finally, cell differentiation is a gradual process, not all-or-nothing, and the statement is irrelevant to the development of the optic cup and lens.
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What is the function of anti-Müllerian hormone (AMH)?
What is the function of anti-Müllerian hormone (AMH)?
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Anti-Mullerian hormone is present only in male fetuses. It is responsible for the degeneration of the Mullerian ducts, which form the oviducts, uterus, and upper vagina in females.
Anti-Mullerian hormone is present only in male fetuses. It is responsible for the degeneration of the Mullerian ducts, which form the oviducts, uterus, and upper vagina in females.
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A deficiency of calcium in the diet can result in which of the following conditions?
A deficiency of calcium in the diet can result in which of the following conditions?
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Osteoporosis is a disease that causes a decrease in bone mass and density and can be induced by malnutrition or calcium deficiency. Even if the disease appears unfamiliar, the prefix "osteo-" indicates a relationship to bone, which is closely linked to calcium levels int he body.
Calcium is also an important ion involved in neural action potentials; it is responsible for triggering the release of neurotransmitters into the synaptic cleft. A calcium deficiency may cause improper action potentials that result in spasms.
Osteoporosis is a disease that causes a decrease in bone mass and density and can be induced by malnutrition or calcium deficiency. Even if the disease appears unfamiliar, the prefix "osteo-" indicates a relationship to bone, which is closely linked to calcium levels int he body.
Calcium is also an important ion involved in neural action potentials; it is responsible for triggering the release of neurotransmitters into the synaptic cleft. A calcium deficiency may cause improper action potentials that result in spasms.
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When a neuron is unable to produce another action potential no matter how much stimulation is provided, what period is the neuron said to be in?
When a neuron is unable to produce another action potential no matter how much stimulation is provided, what period is the neuron said to be in?
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During the absolute refractory period, no action potential can occur. In the relative refractory period, an action potential can occur with more stimulation than is normally required.
During the absolute refractory period, no action potential can occur. In the relative refractory period, an action potential can occur with more stimulation than is normally required.
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Which of the following correctly pairs neuron structure with function?
Which of the following correctly pairs neuron structure with function?
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Voltage-gated calcium channels do not cause depolarization in neurons, but are integral to depolarization in muscle. Voltage-gated sodium channels are responsible for neural depolarization; there are no sodium leaky channels in neurons, as these would disrupt the resting potential. Voltage-gated potassium channels actively import potassium, whereas the sodium-potassium pump actively exports potassium. There is no such thing a potassium-calcium pump.
Voltage-gated calcium channels do not cause depolarization in neurons, but are integral to depolarization in muscle. Voltage-gated sodium channels are responsible for neural depolarization; there are no sodium leaky channels in neurons, as these would disrupt the resting potential. Voltage-gated potassium channels actively import potassium, whereas the sodium-potassium pump actively exports potassium. There is no such thing a potassium-calcium pump.
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During an action potential, depolarization is associated with which of the following?
During an action potential, depolarization is associated with which of the following?
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During depolarization, voltage-gated sodium channels open and allow a rapid influx of sodium ions. The membrane voltage rises from its resting potential of -70 mV to 35 mV. Depolarization is not associated with endocytosis of neurotransmitters.
During depolarization, voltage-gated sodium channels open and allow a rapid influx of sodium ions. The membrane voltage rises from its resting potential of -70 mV to 35 mV. Depolarization is not associated with endocytosis of neurotransmitters.
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Which of the following refers to the process by which action potentials jump from one node of Ranvier to another?
Which of the following refers to the process by which action potentials jump from one node of Ranvier to another?
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The answer is saltatory conduction. Saltatory conduction is the term used to define the process of action potential jumping described in the question. The other possbilities, while involved in the nervous system and its function, do not adaquately describe the process in question.
The answer is saltatory conduction. Saltatory conduction is the term used to define the process of action potential jumping described in the question. The other possbilities, while involved in the nervous system and its function, do not adaquately describe the process in question.
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Which muscle tissue type has the most nuclei per fiber?
Which muscle tissue type has the most nuclei per fiber?
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Skeletal muscle tissue has the most nuclei out of the different types. Cardiac has one or two nuclei per fiber, and smooth muscle cells only have one. This is because of the high metabolic demands of these cells. There is a constant need for protein production and repairs to maintain muscle tissue, processes which originate in the nucleus. It makes sense that skeletal muscle, which is most active and has the highest energy demands, has the greatest number of nuclei.
Skeletal muscle tissue has the most nuclei out of the different types. Cardiac has one or two nuclei per fiber, and smooth muscle cells only have one. This is because of the high metabolic demands of these cells. There is a constant need for protein production and repairs to maintain muscle tissue, processes which originate in the nucleus. It makes sense that skeletal muscle, which is most active and has the highest energy demands, has the greatest number of nuclei.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A scientist shows that the protein labeled "1" has a voltage gate, as well as an inactivation gate, while proteins 2 and 3 lack this dual gate architecture. What ion is most likely to be controlled by protein 1?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
A scientist shows that the protein labeled "1" has a voltage gate, as well as an inactivation gate, while proteins 2 and 3 lack this dual gate architecture. What ion is most likely to be controlled by protein 1?
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Sodium channels have an inactivation gate, as well as a voltage gate. This allows the sodium channels to be turned off, even while voltage changes persist, thereby facilitating repolarization. This dual gate structure also causes the refractory period.
Sodium channels have an inactivation gate, as well as a voltage gate. This allows the sodium channels to be turned off, even while voltage changes persist, thereby facilitating repolarization. This dual gate structure also causes the refractory period.
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In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The protein labeled "2" in the diagram facilitates repolarization following the peak of an action potential. What ion is most likely to be controlled by this protein channel?
In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon.
Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.
The protein labeled "2" in the diagram facilitates repolarization following the peak of an action potential. What ion is most likely to be controlled by this protein channel?
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Potassium is the major species that repolarizes a neuron following depolarization. After sodium has entered the cell to create depolarization, repolarization is driven by potassium ion efflux.
Potassium is the major species that repolarizes a neuron following depolarization. After sodium has entered the cell to create depolarization, repolarization is driven by potassium ion efflux.
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Which important structure(s) line the small intestine and are key for maximizing nutrient absorption?
Which important structure(s) line the small intestine and are key for maximizing nutrient absorption?
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Microvilli surround villa which line the small intestine. These structures greatly increase the surface area (and therefore nutrient absorption capability) of the small intestine.
Microvilli surround villa which line the small intestine. These structures greatly increase the surface area (and therefore nutrient absorption capability) of the small intestine.
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A certain type of plant is only tall when it has a heterozygous genotype. If two heterozygous plants are crossed, what is the probability their offspring will also be tall?
A certain type of plant is only tall when it has a heterozygous genotype. If two heterozygous plants are crossed, what is the probability their offspring will also be tall?
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The cross between two heterozygous plants (Tt and Tt) will result in 25% TT, 50% Tt and 25% tt.
The cross between two heterozygous plants (Tt and Tt) will result in 25% TT, 50% Tt and 25% tt.
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Which of the following is characteristic of a chemical synapse?
I. Signal transmission involves neurotransmitters
II. They are bidirectional
III. They are more common than electrical synapses
Which of the following is characteristic of a chemical synapse?
I. Signal transmission involves neurotransmitters
II. They are bidirectional
III. They are more common than electrical synapses
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A chemical synapse is a type of synapse that uses neurotransmitters to transmit signals. A presynaptic neuron receives an action potential, which prompts neurotransmitters to be released into the synaptic cleft. These neurotransmitters traverse across the synaptic cleft and bind to receptors on the postsynaptic neuron. Binding of neurotransmitters initiates a signal pathway in the postsynaptic neuron.
One of the characteristics of a chemical synapse is that it is unidirectional. This means that the signal can only be propagated in one direction. The signal is always transmitted from the presynaptic to the postsynaptic neuron, never the other way around.
Chemical synapses are indeed more common than electrical synapses. Most nerves, neuromuscular junctions, and major organs in the body use chemical synapses to transmit action potentials. The only major exception is the heart; cardiac cells in the heart use electrical synapses to transmit signal from one cell to the other.
A chemical synapse is a type of synapse that uses neurotransmitters to transmit signals. A presynaptic neuron receives an action potential, which prompts neurotransmitters to be released into the synaptic cleft. These neurotransmitters traverse across the synaptic cleft and bind to receptors on the postsynaptic neuron. Binding of neurotransmitters initiates a signal pathway in the postsynaptic neuron.
One of the characteristics of a chemical synapse is that it is unidirectional. This means that the signal can only be propagated in one direction. The signal is always transmitted from the presynaptic to the postsynaptic neuron, never the other way around.
Chemical synapses are indeed more common than electrical synapses. Most nerves, neuromuscular junctions, and major organs in the body use chemical synapses to transmit action potentials. The only major exception is the heart; cardiac cells in the heart use electrical synapses to transmit signal from one cell to the other.
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In a chemical synapse, which structure contains the neurotransmitter receptors?
In a chemical synapse, which structure contains the neurotransmitter receptors?
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In a chemical synapse, the presynaptic neuron transmits a signal to the adjacent postsynaptic neuron. The postsynaptic neuron receives this signal via neurotransmitters. Recall that a neuron has directionality, with dendrites on one end and an axon on the other end. Dendrites receive an outside signal (signal enters neuron), whereas an axon transmits the signal to an adjacent neuron or muscle (signal exits neuron). This means that the axon end of the presynaptic neuron transmits the signal to the dendrite end of the postsynaptic neuron via a chemical synapse.
In a chemical synapse, the presynaptic neuron transmits a signal to the adjacent postsynaptic neuron. The postsynaptic neuron receives this signal via neurotransmitters. Recall that a neuron has directionality, with dendrites on one end and an axon on the other end. Dendrites receive an outside signal (signal enters neuron), whereas an axon transmits the signal to an adjacent neuron or muscle (signal exits neuron). This means that the axon end of the presynaptic neuron transmits the signal to the dendrite end of the postsynaptic neuron via a chemical synapse.
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Tetrodotoxin TXX is a poison commonly found in pufferfish that blocks the voltage-gated Na+ channels. Which of the following is a most likely consequence of TXX ingestion?
Tetrodotoxin TXX is a poison commonly found in pufferfish that blocks the voltage-gated Na+ channels. Which of the following is a most likely consequence of TXX ingestion?
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During normal impulse conduction, 3 Na+ ions move out of a neuron while 2 K+ ions move in. This results in a high concentration of Na+ outside the cell and low K+ outside the cell. TXX will disrupt the electrochemical gradient by blocking the Na+/K+ voltage-gated channel. A patient suffering from TXX intoxication usually dies from respiratory paralysis brought on by the disruption of neural conduction along nerve fibers and axons. The most appropriate response to the question is the disrupted conduction of nerve impulses.
During normal impulse conduction, 3 Na+ ions move out of a neuron while 2 K+ ions move in. This results in a high concentration of Na+ outside the cell and low K+ outside the cell. TXX will disrupt the electrochemical gradient by blocking the Na+/K+ voltage-gated channel. A patient suffering from TXX intoxication usually dies from respiratory paralysis brought on by the disruption of neural conduction along nerve fibers and axons. The most appropriate response to the question is the disrupted conduction of nerve impulses.
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