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Question 1
Correct
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Regarding the human cell, which of the following cell organelles is responsible for the production of ATP:
Your Answer: Mitochondria
Explanation:Mitochondria are membrane-bound organelles that are responsible for the production of the cell’s supply of chemical energy. This is achieved by using molecular oxygen to utilise sugar and small fatty acid molecules to generate adenosine triphosphate (ATP). This process is known as oxidative phosphorylation and requires an enzyme called ATP synthase. ATP acts as an energy-carrying molecule and releases the energy in situations when it is required to fuel cellular processes. Mitochondria are also involved in other cellular processes, including Ca2+homeostasis and signalling. Mitochondria contain a small amount of maternal DNA.Mitochondria have two phospholipid bilayers, an outer membrane and an inner membrane. The inner membrane is intricately folded inwards to form numerous layers called cristae. The cristae contain specialised membrane proteins that enable the mitochondria to synthesise ATP. Between the two membranes lies the intermembrane space, which stores large proteins that are required for cellular respiration. Within the inner membrane is the perimitochondrial space, which contains a jelly-like matrix. This matrix contains a large quantity of ATP synthase.Mitochondrial disease, or mitochondrial disorder, refers to a group of disorders that affect the mitochondria. When the number or function of mitochondria in the cell are disrupted, less energy is produced and organ dysfunction results.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 2
Correct
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What type of pump is the Na+/K+ATPase pump?
Your Answer: An antiporter
Explanation:In order for primary active transport to pump ions against their electrochemical gradient, chemical energy is used in the form of ATP. This is facilitated by the Na+/K+-ATPase antiporter pump, which uses metabolic energy to move 3 Na+ions out of the cell for every 2 K+ions that come in, against their respective electrochemical gradients. As a result, the cell the maintains a high intracellular concentration of K+ions and a low concentration of Na+ions.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 3
Incorrect
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Regarding the resting membrane potential, which of the following statements is CORRECT:
Your Answer: The resting membrane potential is primarily determined by the Na + equilibrium potential.
Correct Answer: The resting cell membrane is more permeable to K + ions than to Na + ions.
Explanation:A membrane potential is a property of all cell membranes, but the ability to generate an action potential is only a property of excitable tissues. The resting membrane is more permeable to K+and Cl-than to other ions (and relatively impermeable to Na+); therefore the resting membrane potential is primarily determined by the K+equilibrium potential. At rest the inside of the cell is negative relative to the outside. In most neurones the resting potential has a value of approximately -70 mV.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 4
Incorrect
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Regarding transport across a membrane, which of the following statements is CORRECT:
Your Answer: Facilitated diffusion is an active process requiring metabolic energy.
Correct Answer: Ion channels may be voltage-gated or ligand-gated.
Explanation:Diffusion is the passive movement of ions across a cell membrane down their electrochemical or concentration gradient through ion channels. Ion channels can be voltage-gated (regulated according to the potential difference across the cell membrane) or ligand-gated (regulated by the presence of a specific signal molecule). Facilitated diffusion is the process of spontaneous passive transport of molecules or ions down their concentration gradient across a cell membrane via specific transmembrane transporter (carrier) proteins. The energy required for conformational changes in the transporter protein is provided by the concentration gradient rather than by metabolic activity. In secondary active transport there is no direct coupling of ATP but the initial Na+ electrochemical gradient that drives the secondary active transport is set up by a process that requires metabolic energy. Examples include the sodium/calcium exchanger, or the sodium/glucose symporter.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 5
Incorrect
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Regarding platelets, which of the following statements is CORRECT:
Your Answer: Normally about 60% of the total body pool of platelets is stored in the spleen.
Correct Answer: Platelets are produced in the bone marrow by fragmentation of the cytoplasm of megakaryocytes.
Explanation:Platelets are produced in the bone marrow by fragmentation of the cytoplasm of megakaryocytes, derived from the common myeloid progenitor cell. The time interval from differentiation of the human stem cell to the production of platelets averages 10 days. Thrombopoietin is the major regulator of platelet formation and 95% of this is produced by the liver. The normal platelet count is approximately 150 – 450 x 109/L and the normal platelet lifespan is 10 days. Under normal circumstances, about one-third of the marrow output of platelets may be trapped at any one time in the normal spleen.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 6
Incorrect
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Which of the following statements is incorrect regarding the Na+/K+ATPase pump?
Your Answer: The Na + /K + ATPase pump facilitates movement by primary active transport.
Correct Answer: The Na + /K + ATPase pump moves 3 Na + ions into the cell for every 2 K + ions out.
Explanation:In order for primary active transport to pump ions against their electrochemical gradient, chemical energy is used in the form of ATP. The Na+/K+-ATPase antiporter pump uses metabolic energy to move 3 Na+ions out of the cell for every 2 K+ions in, against their respective electrochemical gradients. As a result, the cell the maintains a high intracellular concentration of K+ions and a low concentration of Na+ions.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 7
Incorrect
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Regarding haemoglobin, which of the following statements is INCORRECT:
Your Answer: Haem synthesis occurs largely in the mitochondria.
Correct Answer: Haemoglobin synthesis occurs in mature erythrocytes.
Explanation:Haemoglobin is composed of four polypeptide globin chains each with its own iron containing haem molecule. Haem synthesis occurs largely in the mitochondria by a series of biochemical reactions commencing with the condensation of glycine and succinyl coenzyme A under the action of the key rate-limiting enzyme delta-aminolevulinic acid (ALA) synthase. The globin chains are synthesised by ribosomes in the cytosol. Haemoglobin synthesis only occurs in immature red blood cells.There are three types of haemoglobin in normal adult blood: haemoglobin A, A2 and F:- Normal adult haemoglobin (HbA) makes up about 96 – 98 % of total adult haemoglobin, and consists of two alpha (α) and two beta (β) globin chains. – Haemoglobin A2 (HbA2), a normal variant of adult haemoglobin, makes up about 1.5 – 3.5 % of total adult haemoglobin and consists of two α and two delta (δ) globin chains.- Foetal haemoglobin is the main Hb in the later two-thirds of foetal life and in the newborn until approximately 12 weeks of age. Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin. Red cells are destroyed by macrophages in the liver and spleen after , 120 days. The haem group is split from the haemoglobin and converted to biliverdin and then bilirubin. The iron is conserved and recycled to plasma via transferrin or stored in macrophages as ferritin and haemosiderin. An increased rate of haemoglobin breakdown results in excess bilirubin and jaundice.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 8
Incorrect
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In the extrinsic pathway of the coagulation cascade, the tenase complex is:
Your Answer: Factor IXa-Va complex
Correct Answer: Factor VIIa-tissue factor complex
Explanation:The extrinsic pathway for initiating the formation of prothrombin activator begins with a traumatized vascular wall or traumatized extravascular tissues that come in contact with the blood. Exposed and activated by vascular injury, with plasma factor VII. The extrinsic tenase complex, factor VIIa-tissue factor complex, activates factor X to factor Xa.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 9
Correct
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Which of the following globin chains makes up normal adult haemoglobin (HbA)?
Your Answer: Two alpha and two beta chains
Explanation:Total adult haemoglobin comprises about 96 – 98 % of normal adult haemoglobin (HbA). It consists of two alpha (α) and two beta (β) globin chains.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 10
Incorrect
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The correct statement regarding the parasympathetic nervous system is which of the following?
Your Answer: Parasympathetic postganglionic neurones release acetylcholine which acts on cholinergic nicotinic receptors.
Correct Answer: Parasympathetic preganglionic neurones run in cranial nerves III, VII, IX and X.
Explanation:The electron transfer system is responsible for most of the energy produced during respiration. The is a system of hydrogen carriers located in the inner mitochondrial membrane. Hydrogen is transferred to the electron transfer system via the NADH2 molecules produced during glycolysis and the Krebs cycle. As a result, a H+ion gradient is generated across the inner membrane which drives ATP synthase. The final hydrogen acceptor is oxygen and the H+ions and O2 combine to form water.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 11
Correct
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Parasympathetic preganglionic neurons originate in which of the following locations:
Your Answer: Brainstem and pelvic splanchnic nerves
Explanation:Parasympathetic preganglionic neurones originate in the brainstem from which they run in cranial nerves III, VII, IX and X and also from the second and third sacral segments of the spinal cord. Parasympathetic preganglionic neurones release acetylcholine into the synapse, which acts on cholinergic nicotinic receptors on the postganglionic fibre. Parasympathetic peripheral ganglia are generally found close to or within their target, whereas sympathetic peripheral ganglia are located largely in two sympathetic chains on either side of the vertebral column (paravertebral ganglia), or in diffuse prevertebral ganglia of the visceral plexuses of the abdomen and pelvis. Parasympathetic postganglionic neurones release acetylcholine, which acts on cholinergic muscarinic receptors.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 12
Incorrect
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Regarding the refractory period, which of the following statements is INCORRECT:
Your Answer: The relative refractory period is due to a temporary hyperpolarisation.
Correct Answer: Action potentials can occur in the relative refractory period but the amplitude of the action potential is smaller.
Explanation:Following the action potential, Na+channels remain inactive for a time in a period known as the absolute refractory period where they cannot be opened by any amount of depolarisation. Following this there is a relative refractory period where the temporary hyperpolarisation (due to delayed closure of rectifier K+channels) makes the cell more difficult to depolarise and an action potential can be generated only in response to a larger than normal stimulus. The refractory period limits the frequency at which action potentials can be generated, and ensures that, once initiated, an action potential can travel only in one direction. An action potential is an all or nothing response so the amplitude of the action potential cannot be smaller.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 13
Correct
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What is the approximate lifespan of the mature erythrocyte:
Your Answer: 120 days
Explanation:Erythrocytes have a normal lifespan of about 120 days. Mature erythrocytes are biconcave discs with no nucleus, ribosomes or mitochondria but with the ability to generate energy as ATP by the anaerobic glycolytic pathway. The red cell membrane consists of a bipolar lipid layer with a membrane skeleton of penetrating and integral proteins anchoring carbohydrate surface antigens. The shape and flexibility of red cells allows them to deform easily and pass through capillaries.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 14
Correct
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Which of the following ions normally has the highest concentration in intracellular fluid:
Your Answer: K +
Explanation:Potassium (K+) is the principal intracellular ion; approximately 4 mmol/L is extracellular (3%) and 140 mmol/L intracellular (97%).
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 15
Correct
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How does an action potential in the motor end plate rapidly spread to the central portions of the muscle cells?
Your Answer: Transverse tubules
Explanation:When the concentration of intracellular Ca2+rises, muscle contraction occurs. The pathway of an action potential is down tube-shaped invaginations of the sarcolemma called T-tubules (transverse tubules). These penetrate throughout the muscle fibre and lie adjacent to the terminal cisternae of the sarcoplasmic reticulum. The voltage changes in the T-tubules result in the opening of sarcoplasmic reticulum Ca2+channels and there is there is release of stored Ca2+into the sarcoplasm. Thus muscle contraction occurs via excitation-contraction coupling (ECC) mechanism.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 16
Correct
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From which of the following cell types are platelets derived?
Your Answer: Megakaryocytes
Explanation:Synthesis of platelets occurs in the bone marrow by fragmentation of megakaryocytes cytoplasm, derived from the common myeloid progenitor cell. The average time for differentiation of the human stem cell to the production of platelets is about 10 days. The major regulator of platelet formation is thrombopoietin and 95% of this is produced by the liver. Normal platelet count is 150 – 450 x 109/L and the normal lifespan of a platelet is about 10 days. Usually about one-third of the marrow output of platelets may be trapped at any one time in the normal spleen.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 17
Correct
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Which of the following statements is correct regarding homeostasis?
Your Answer: In negative feedback mechanisms, effectors always act to move the variable in the opposite direction to the change that was originally detected.
Explanation:The vast majority of systems within the body work by negative feedback mechanisms. This negative feedback refers to the way that effectors act to move the variable in the opposite direction to the change that was originally detected. Because there is an inherent time delay between detecting a change in a variable and effecting a response, the negative feedback mechanisms cause oscillations in the variable they control. There is a narrow range of values within which a normal physiological function occurs and this is called the ‘set point’. The release of oxytocin in childbirth is an example of positive feedback.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 18
Correct
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You are seeing a child with known mitochondrial disease who has presented breathlessness and cough. Which of the following best describes the function of mitochondria:
Your Answer: Energy production
Explanation:Mitochondria are membrane-bound organelles that are responsible for the production of the cell’s supply of chemical energy. This is achieved by using molecular oxygen to utilise sugar and small fatty acid molecules to generate adenosine triphosphate (ATP). This process is known as oxidative phosphorylation and requires an enzyme called ATP synthase. ATP acts as an energy-carrying molecule and releases the energy in situations when it is required to fuel cellular processes. Mitochondria are also involved in other cellular processes, including Ca2+homeostasis and signalling. Mitochondria contain a small amount of maternal DNA.Mitochondria have two phospholipid bilayers, an outer membrane and an inner membrane. The inner membrane is intricately folded inwards to form numerous layers called cristae. The cristae contain specialised membrane proteins that enable the mitochondria to synthesise ATP. Between the two membranes lies the intermembrane space, which stores large proteins that are required for cellular respiration. Within the inner membrane is the perimitochondrial space, which contains a jelly-like matrix. This matrix contains a large quantity of ATP synthase.Mitochondrial disease, or mitochondrial disorder, refers to a group of disorders that affect the mitochondria. When the number or function of mitochondria in the cell are disrupted, less energy is produced and organ dysfunction results.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 19
Incorrect
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Regarding fluid balance, which of the following statements is CORRECT:
Your Answer: Osmosis is the passive movement of water from regions of high solute concentration to regions of low solute concentration.
Correct Answer: About three-quarters of extracellular fluid is interstitial.
Explanation:An ‘average’ person (70 kg male) contains about 40 litres of water in total, separated into different fluid compartments by biological semipermeable membranes; plasma cell membranes between extracellular and intracellular fluid, and capillary walls between interstitial and intravascular fluid. Around two-thirds of the total fluid (27 L) is intracellular fluid (ICF) and one-third of this (13 L) is extracellular fluid (ECF). The ECF can be further divided into intravascular fluid (3.5 L) and interstitial fluid (9.5 L). Transcellular fluid refers to any fluid that does not contribute to any of the main compartments but which are derived from them e.g. gastrointestinal secretions and cerebrospinal fluid, and has a collective volume of approximately 2 L.Osmosis is the passive movement of water across a semipermeable membrane from regions of low solute concentration to those of higher solute concentration.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 20
Incorrect
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Regarding skeletal muscle, which of the following best describes the Z-line:
Your Answer: A line dividing the thick and the thin myofilaments
Correct Answer: A line dividing muscle fibres into sarcomeres
Explanation:Each muscle fibre is divided at regular intervals along its length into sarcomeres separated by Z-lines. The sarcomere is the functional unit of the muscle.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 21
Correct
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Foetal haemoglobin (HbF) comprises about how much of the total haemoglobin in adults:
Your Answer: 0.5 - 0.8%
Explanation:Foetal haemoglobin (HbF) makes up about 0.5 – 0.8 % of total adult haemoglobin and consists of two α and two gamma (γ) globin chains.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 22
Correct
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Regarding haemoglobin, which of the following statements is CORRECT:
Your Answer: In degradation of haemoglobin, the haem group is split from the haemoglobin and converted to biliverdin and ultimately to bilirubin.
Explanation:Haemoglobin is composed of four polypeptide globin chains each with its own iron containing haem molecule. Haem synthesis occurs largely in the mitochondria by a series of biochemical reactions commencing with the condensation of glycine and succinyl coenzyme A under the action of the key rate-limiting enzyme delta-aminolevulinic acid (ALA) synthase. The globin chains are synthesised by ribosomes in the cytosol. Haemoglobin synthesis only occurs in immature red blood cells.There are three types of haemoglobin in normal adult blood: haemoglobin A, A2 and F:- Normal adult haemoglobin (HbA) makes up about 96 – 98 % of total adult haemoglobin, and consists of two alpha (α) and two beta (β) globin chains. – Haemoglobin A2 (HbA2), a normal variant of adult haemoglobin, makes up about 1.5 – 3.5 % of total adult haemoglobin and consists of two α and two delta (δ) globin chains.- Foetal haemoglobin is the main Hb in the later two-thirds of foetal life and in the newborn until approximately 12 weeks of age. Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin. Red cells are destroyed by macrophages in the liver and spleen after , 120 days. The haem group is split from the haemoglobin and converted to biliverdin and then bilirubin. The iron is conserved and recycled to plasma via transferrin or stored in macrophages as ferritin and haemosiderin. An increased rate of haemoglobin breakdown results in excess bilirubin and jaundice.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 23
Incorrect
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Which of the following statements is correct regarding the neuronal action potential?
Your Answer: Action potentials can have a graded response depending on the stimuli.
Correct Answer: Initial depolarisation occurs as a result of a Na + influx.
Explanation:The resting potential in most neurons has a value of approximately -70 mV. The threshold potential is generally around -55 mV. Initial depolarisation when there is Na+influx through ligand-gated Na+channels. Action potential is an all or nothing response. The size of the action potential is constant and so, the intensity of the stimulus is coded by the frequency of firing of a neuron. K+efflux is responsible for repolarisation.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 24
Correct
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Which of the following statements is incorrect regarding the electron transfer system?
Your Answer: The electron transfer system occurs in anaerobic respiration.
Explanation:The electron transfer system is responsible for most of the energy produced during respiration. The is a system of hydrogen carriers located in the inner mitochondrial membrane. Hydrogen is transferred to the electron transfer system via the NADH2molecules produced during glycolysis and the Krebs cycle. As a result, a H+ion gradient is generated across the inner membrane which drives ATP synthase. The final hydrogen acceptor is oxygen and the H+ions and O2 combine to form water.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 25
Correct
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The only statement that is correct regarding diffusion is which of the following?
Your Answer: The permeability of a membrane is related to the membrane thickness and composition.
Explanation:Passive diffusion is a process that describes the movement down a concentration gradient. This process accounts for movement across small distances like within the cytosol or across membranes. Factors that affect the diffusion of a substance across a membrane are the permeability (p) of the membrane, a difference in concentration across the membrane and the membrane area over which diffusion occurs. The membrane thickness and composition, and the diffusion coefficient of the substance also affects the permeability. Fick’s law describes the rate of diffusion of a substance within a solution, which can be modified to describe the rate of diffusion across a membrane.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 26
Correct
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The resting membrane potential of a neurone is usually about:
Your Answer: -70 mV
Explanation:In most neurones the resting potential has a value of approximately -70 mV. The threshold potential is generally around -55 mV. Initial depolarisation occurs as a result of a Na+influx through ligand-gated Na+channels. Action potential is an all or nothing response; because the size of the action potential is constant, the intensity of the stimulus is coded by the frequency of firing of a neuron. Repolarisation occurs primarily due to K+efflux.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 27
Correct
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Which of the following neurotransmitter and receptor combinations is present at the neuromuscular junction:
Your Answer: Acetylcholine acting at nicotinic receptors
Explanation:At the neuromuscular junction, acetylcholine is released from the prejunctional membrane which acts on cholinergic nicotinic receptors on the postjunctional membrane.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 28
Correct
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Which of these is NOT a naturally occurring anticoagulant:
Your Answer: Factor V Leiden
Explanation:It’s crucial that thrombin’s impact is restricted to the injured site. Tissue factor pathway inhibitor (TFPI), which is produced by endothelial cells and found in plasma and platelets, is the first inhibitor to function. It accumulates near the site of harm induced by local platelet activation. Xa and VIIa, as well as tissue factor, are inhibited by TFPI. Other circulating inhibitors, the most potent of which is antithrombin, can also inactivate thrombin and other protease factors directly. Coagulation cofactors V and VIII are inhibited by protein C and protein S. Tissue plasminogen activator (TPA) from endothelial cells facilitates fibrinolysis by promoting the conversion of plasminogen to plasmin.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 29
Correct
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Which of the following ions is more abundant in extracellular fluid than in intracellular fluid:
Your Answer: Cl -
Explanation:Protein and phosphate are the primary intracellular anions, while chloride (Cl-) and bicarbonate are the predominant extracellular anions (HCO3-).
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 30
Correct
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Which of the following statements is not true regarding ion channels?
Your Answer: Ion channels provide a charged, hydrophobic pore through which ions can diffuse across the lipid bilayer.
Explanation:Ion channels are pore-forming protein complexes that facilitate the flow of ions across the hydrophobic core of cell membranes. They are present in the plasma membrane and membranes of intracellular organelles of all cells, and perform essential physiological functions. They provide a charged, hydrophilic pore through which ions can move across the lipid bilayer. They are selective for particular ions and their pores may be opened or closed. Because of this ability to open and close, ion channels allow the cell to have the ability to closely control the movement of ions across the membrane. Gating refers to the transition between an open and closed ion channel state, and is brought about by a conformationational change in the protein subunits that open or close the ion-permeable pore. Ion channels can be:1. voltage-gated these are regulated according to the potential difference across the cell membrane or2. ligand-gated – these are regulated by the presence of a specific signal molecule.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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SESSION STATS - PERFORMANCE PER SPECIALTY
