BIOCHEM C785 POSSIBLE FINAL EXAM 2021

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Myoglobin and hemoglobin each have different numbers of subunits and this affects their respective oxygen storage and delivery capabilities. How many subunits do myoglobin and hemoglobin each have? ... Select one: a. Two, Three b. One, Two c. One, Four Correct! Myoglobin consist of one and hemoglobin consists of four subunits. The number of subunits affects their respective oxygen storage and delivery capabilities. d. Four, One Addition of ______________________alters the shape of the iron–heme complex, and therefore its absorption of light as indicated by its color change from dark purple (the color of hemoglobin in venous blood) to brilliant scarlet (the color of hemoglobin in arterial blood). Select one: a. iron b. oxygen Correct! c. globin subunit d. porphyrin Oxygen binding alters the structure of an entire hemoglobin tetramer, so the structures of oxyhemoglobin and deoxyhemoglobin are noticeably different. The oxyhemoglobin conformation is specifically referred to as the __________ state, whereas the deoxyhemoglobin conformation is referred to as the __________ state. Select one: a. O and D b. Oxygenated and Deoxygenated c. Relaxed or R and Tense or T Correct! Oxygen binding causes a marked change in hemoglobin structure. In the presence of oxygen, hemoglobin is in the Relaxed state or R state. In the absence of oxygen, hemoglobin is in the Tense state or T state. d. There is no difference between the two states Patients with sickle cell anemia have atypical hemoglobin, which will distort the red blood cells into sickle shape during oxygen delivery. The substitution of a hydrophilic amino acid with a ____________amino acid in hemoglobin subunits results in the polymerization of hemoglobin, leading to the sickling of red blood cells. Select one: a. hydrophobic Correct! In case of sickle cell anemia, a hydrophilic amino acid-glutamate is replaced by a non polar-hydrophobic amino acid-valine, leading to polymerization of hemoglobin, fibril formation and eventually sickling of the red blood cells. b. cysteine c. polar This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com d. hydrophilic Hemglobin consists of four proteins subunits. Each subunit contains a heme group that holds an iron atom, which can bind to an oxygen molecule. When binding hemoglobin or myoglobin, CO binds in place of _________. Select one: a. Iron b. Oxygen Correct! CO binds in place of oxygen. c. Histidine d. Heme Structurally, hemoglobin can bind ___ molecules of oxygen, all of which could potentially be replaced by carbon monoxide. Select one: a. 4 Correct! b. 2 c. 1 d. 3 Carbon monoxide outcompetes oxygen for attachment to the __________ group of hemoglobin where it is permanently, covalently attached. Select one: a. histidine b. sulfide c. ligand d. heme Correct As carbon monoxide binds to hemoglobin, the protein subunits change conformation to allow carbon monoxide to bind faster. This process is called __________. Select one: a. positive cooperativity Correct! Binding of one carbon monoxide molecule changes the conformation of the hemoglobin in a fashion such that more molecules of carbon monoxide can bind to the same protein. b. competitive inhibition c. non-competitive inhibition d. allosteric binding This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com Carbon monoxide shifts the Oxygen-Hemoglobin Dissociation Curve to the left, while carbon dioxide shifts this curve to the right. Based on your knowledge of the Bohr Effect, which of the following statements is true? Select one: a. Carbon dioxide and carbon monoxide decrease hemoglobin’s affinity for oxygen. Incorrect. b. Carbon dioxide and carbon monoxide have no impact on hemoglobin’s affinity for oxygen. c. Carbon dioxide increases hemoglobin’s affinity for oxygen, while carbon monoxide decreases it. d. Carbon dioxide decreases hemoglobin’s affinity for oxygen, while carbon monoxide increases it Carbon dioxide, released by the respiring cells, combines with the water molecules of plasma to form carbonic acid. Carbonic acid increases the H+ ion concentration (low or acidic pH). H+ ions stabilize the deoxy-conformation (T state) of hemoglobin and allow oxygen release and delivery to the tissues. On the other hand, carbon monoxide, which has a very high affinity for hemoglobin than oxygen, binds and maintains hemoglobin in oxy-conformation (R state). Oxy-conformation of HB is amenable to further binding of carbon monoxide and shifts the Oxygen-Hemoglobin Dissociation Curve to the left. Hemoglobin’s cooperative binding behavior is key to its physiological function. The binding of which of the following molecules influences this behavior? Select one: a. Heme b. None of these c. Oxygen Correct! d. Iron Carbonic anhydrase is an important __________ present in the red blood cells that aids in efficient transportation of carbon dioxide in the form of _________, from tissues to lungs. Select one: a. enzyme, carbon dioxide b. chemical, carbon monoxide c. substrate, bicarbonate ions d. enzyme, bicarbonate ions Correct! Carbonic anhydrase is an enzyme which catalyzes the conversion of carbon dioxide to bicarbonate ions. This mechanism enables efficient transport of carbon dioxide by warding off bubble formation in the blood. Hemoglobin’s ability to bind or release oxygen depends on the pH of the environment. This behavior is known as the Bohr effect. Considering this, which of the following statements is true? Select one: a. At high pH hemoglobin is able to bind and release oxygen. IncorrectIncorrect. This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com b. Hemoglobin binds to the oxygen at low pH and releases oxygen at high pH. c. At low pH hemoglobin is able to bind and release oxygen. d. Hemoglobin binds to the oxygen at high pH and releases oxygen at low pH. pH is a measure of H+ ion concentration. High pH indicates a more basic environment in which the H+ ion concentration is low, as seen in the lungs. Under these conditions, hemoglobin binds more oxygen. Low pH indicates an acidic environment in which the H+ ion concentration is high. Such conditions encourage the binding of H+ ions to hemoglobin and stabilizing a form of hemoglobin which decreases the affinity for oxygen, resulting in release of oxygen. Hemoglobin acts as a buffer and controls the pH of the blood by binding to __________. Select one: a. H+ ions Correct! A high concentration of H+ ions, if left unbound, will result in an acidic environment (low pH value). Hemoglobin by binding b. oxygen c. bicarbonate ion d. carbon dioxide In the lungs, the CO2 concentration is low and the pH is high, while in the tissues, the CO2 concentration is high and the pH is low. In locations where the pH is low, hemoglobin will be in the T state, allowing it to release oxygen more effectively. Increased levels of 2,3-BPG will decrease the affinity for oxygen by binding to and stabilizing the T state of hemoglobin. The action of 2,3-BPG allows hemoglobin to release oxygen more effectively, which is similar to the effect of low pH on the action of hemoglobin. In comparison to adult hemoglobin, fetal hemoglobin has a higher affinity for oxygen because it doesn’t bind 2-3BPG well. Which statement about hemoglobin binding to carbon monoxide (CO) is true? Select one: a. Hb binds to CO with a lower affinity than oxygen and stabilizes the R state. b. Hb binds to CO with a higher affinity than oxygen and stabilizes the T state. Incorrect. CO has a higher affinity for hemoglobin than oxygen, and this binding stabilizes the R state. This means that any oxygen that does bind to hemoglobin remains bound and is therefore unavailable to the body's cells. c. Hb binds to CO with a higher affinity than oxygen and stabilizes the R state. d. Hb binds to CO with a lower affinity than oxygen and stabilizes the T state. When hemoglobin changes from T to R, it has ________ affinity for oxygen. This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com Select one: a. zero b. low Incorrect. The R state has a higher affinity for oxygen than the T state. c. high d. none of these are correct When hemoglobin changes from R to T, it has _______________ affinity for oxygen. Select one: a. low b. high Incorrect. The T state has a lower affinity for oxygen than the R state. c. zero d. none of these are correct Cooperativity refers to _____. Select one: a. the exchange of oxygen that happens in the placenta between maternal and fetal blood b. The ability of hemoglobin to supply the RBC with oxygen for ATP production c. hemoglobin structural changes that increase its affinity for oxygen. Correct! The four subunits of hemoglobin, along with the heme groups, communicate or "cooperate" with each other to increase hemoglobin's affinity for oxygen. When oxygen binds to the iron atom in a heme group, the heme changes from a bent to a planar state. The change in the heme shape also "tugs" on the protein chain holding the heme group, causing a conformational shift in the protein subunit. Once one subunit has undergone the conformational shift, it influences the conformations of the neighboring subunits such that oxygen binding occurs more easily. d. The increased affinity for oxygen that myoglobin has when oxygen concentration is low When the oxygen concentration is high, the heme shape is _____________. When the oxygen concentration is low, the heme shape is ______________shape. Select one: a. bent (non-planar), bent (non-planar) b. planar, planar c. bent (non-planar) , planar Incorrect. When oxygen concentration is high, the oxygen binds to iron which pulls the iron and brings heme into a planar position. When oxygen is low, the iron is deoxygenated and the heme is then bent. d. planar, bent (non-planar) The Bohr effect is a relationship between hemoglobin's oxygen binding behavior in conjunction with the pH of the surroundings. When the pH is low, hemoglobin has _____________ affinity for oxygen and ________ oxygen. Select one: a. low, releases This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com b. low, binds c. high, releases d. high, binds Incorrect. Low pH induces the T state which decreases hemoglobin affinity for oxygen; hemoglobin releases oxygen . Bohr effect is a relationship between hemoglobin's oxygen binding behavior in conjunction with the pH of the surroundings. When the pH is high, hemoglobin has _____________ affinity for oxygen and ________ oxygen. Select one: a. low, binds b. high, releases c. high, binds d. low, releases Incorrect. High pH induces the R state which increases hemoglobin's affinity for oxygen so oxygen would remain bound. Relative to the lungs, the pH in the peripheral tissues is _______ because __________________. Select one: a. lower, the CO2 generated by metabolism is converted to bicarbonate, which releases protons (H+). b. higher, the concentration of CO2 decreases. Incorrect. The pH of the tissue is lower than in the lungs because the concentration of CO2 increases. This CO2 is converted to bicarbonate by the enzyme carbonic anhydrase. Bicarbonate releases H+ which causes the pH to decrease. c. lower, the concentration of oxygen decreases. d. lower, carbonic anhydrase sequesters protons (H+). The Bohr effect is a relationship between hemoglobin's oxygen binding behavior in conjunction with the pH of the surroundings. When the H+ ion concentration increases, the pH of the solution _________________. Select one: a. decreases b.changes only if the oxygen concentration increases c. increases Incorrect. pH is a measure of H+ ion concentration. Since the number calculated for pH is the d. negative of a base 10 logarithm, the more H+ ions present in solution, the lower the pH. does not change Myoglobin stores oxygen, whereas hemoglobin transports oxygen. Which one of the following statements is true? Select one: This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com a. Myoglobin has a higher affinity for oxygen compared to hemoglobin Correct! At lower oxygen concentrations, a much higher fraction of myoglobin would be saturated with oxygen compared to hemoglobin. b. Hemoglobin and myoglobin both have the same affinity for oxygen c. Hemoglobin has a higher affinity for oxygen compared to myoglobin d. Myoglobin has exactly one-quarter of the affinity for oxygen because it has only one subunit Hemoglobin is an oxygen transport protein, whereas myoglobin is an oxygen storage protein. They exhibit different binding curves when plotted on a graph with total partial pressure of the oxygen (x-axis) plotted against the percentage saturation of hemoglobin (y-axis). Which pattern of binding curves do these proteins exhibit? Select one: a. Myoglobin has a sigmoidal curve whereas the hemoglobin has a hyperbolic curve b. Both have a sigmoidal binding curve c. Hemoglobin has a sigmoidal curve whereas the myoglobin has a hyperbolic curve Correct! Myoglobin has a much higher affinity for oxygen with percent saturation increasing rapidly in low oxygen concentrations; this is demonstrated by a hyperbolic curve. Hemoglobin initially binds to oxygen at a slower rate at low oxygen concentrations, demonstrated by a sigmoidal curve. d. Both have a hyperbolic binding curve Hemoglobin and myoglobin proteins bind to molecular oxygen. However, the protein part of the hemoglobin does not bind directly to the oxygen. Instead, a specific atom helps bind the oxygen. Which one of the following will help hemoglobin directly bind to the oxygen? Select one: a. Heme b. Iron Correct! Iron is the atom that binds directly with oxygen. c. Carbon monoxide d. Histidine The symptoms of sickle cell anemia are primarily because red blood cells are misshaped. This is due to ____. Select one: a. a mutation in the alpha hemoglobin gene which leads to the insertion of valine into the hydrophobic patches on oxygenated hemoglobin. b. a mutation in the beta hemoglobin gene which leads to the insertion of valine into the hydrophobic patches on deoxygenated hemoglobin. c. a mutation in the beta hemoglobin gene which leads to insertion of glutamate into the hydrophobic patches on oxygenated hemoglobin. Incorrect.Glutamate is a charged amino acid; its R group will not interact with a hydrophobic pocket. d. a mutation in the alpha hemoglobin gene which leads to the insertion of valine into the hydrophobic patches on deoxygenated hemoglobin. This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com Relative to the peripheral tissues, the pH in the lungs is _______ because __________________. Select one: a. higher, the protons (H+) that were combined with hemoglobin quickly bind to bicarbonate (HCO3-) to form CO2; the CO2 is then exhaled. b. higher, there is more oxygen in the lungs c. lower, there is more CO2 present. d. lower, the protons (H+) that were combined with hemoglobin quickly bind to bicarbonate (HCO3-) to form CO2; the CO2 is then exhaled. Incorrect. Relative to the tissues, the lung tissue has a higher pH because there are fewer protons (H+) in solution. Carbon monoxide is poisonous because Select one: a. it binds hemoglobin 20 times less than oxygen. b. it binds hemoglobin 200 times better than oxygen. Correct! Carbon monoxide has an affinity for hemoglobin that is 200 times stronger than that of oxygen. c. it binds hemoglobin 200 times less than oxygen. d. None of the options are correct. 2,3 BPG stabilizes the _____ state(s) of hemoglobin. Select one: a. R b. R and T c. T Correct! 2,3 BPG stabilizes the T state of hemoglobin. This reduces hemoglobin's affinity for O2 and promotes O2 release to the tissues, in much the same way as low pH. d. None of the options are correct Even though the amino acid sequence between subunits of hemoglobin and myoglobin are not exactly the same, there are other similarities between the two proteins. Which level of protein structure is not found in both molecules? Select one: a. Tertiary b. Quaternary Correct! Myoglobin consists of a single subunit, while hemoglobin has four. Myoglobin has primary, secondary, and tertiary levels of protein structure, however, it does not have a quaternary structure. Any protein composed of only one subunit does not have quaternary structure. c. Primary d. Secondary In the deoxygenated state the heme is ____________, where as in the oxygenated state, the heme is _____________________. This study source was downloaded by 100000812856574 from CourseHero.com on 11-10-2021 05:51:04 GMT -06:00 https://www.coursehero.com/file/26662459/Biochemistry-Module-3docx/ This study resource was shared via CourseHero.com Select one: a. planar, planar b. bent (non-planar), planar c. planar, bent (non-planar) Incorrect. In the deoxygenated state the heme is bent (non-planar), where as in the oxygenated state, the heme is planar. When oxygen binds, the iron is pulled toward the oxygen the the heme flattens to the planar shape. In the absence of oxygen, the histidine residue that binds to the Fe atom will pull on the Fe and distort, or slightly bend, the heme plane. d. bent (non-planar), bent (non-planar) Fetal hemoglobin _____. Select one: a. is never in the R state. b. has the exact same polypeptide chains as adult hemoglobin. c. binds to oxygen tightly at lower oxygen concentrations since its R state is the preferred structure. Correct! Fetal hemoglobin binds oxygen tightly at lower oxygen concentrations since its R state is the preferred structure. d. exhibits an oxygen binding curve that is the same shape as myoglobin oxygen binding curve When the blood pH is low, the heme is in_______________ shape. When the blood pH is high, the heme is in ______________shape. Select one: a. planar, bent (non-planar) Incorrect. When the blood pH is low, the heme is in bent (non-planar) shape because hemoglobin has been deoxygenated. The T state of hemoglobin is favored by low pH and induces the release of oxygen, while the R state is favored by higher pH and stimulates hemoglobin to bind more O2 by increasing its affinity for oxygen. b. planar, planar c. bent (non-planar), planar d. bent (non-planar), bent (non-planar) In which of the following patients is the planar conformation of the heme group in hemoglobin favored? Select one: a. In a firefighter who is brought to the emergency room after entering a burning building Correct! The oxygen concentration is higher in the emergency room than in the burning building. This would favor the R state of the hemoglobin protein, and planar conformation of the heme group. b. In an older woman with pneumonia and sepsis who has a blood pH of 7.1 c. In a girl with diabetic ketoacidosis d. In the muscle capillaries of a patient who is on a treadmill for a cardiac stress test [Show More]

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