Animal Phys: Respiratory Pigments and Gas Exchange

Tadpoles live in an environment with lower oxygen availability than adult frogs. Their blood has a __1__ oxygen, and a smaller__2__shift, than adult frogs.

1. higher affinity for 2. Bohr

Name the structure(s) of respiratory pigments

hemoglobin and hemocyanin

Oxygen diffuses across the respiratory epithelium and binds to a ______ that gives the blood its color.

respiratory pigment

Hemocyanin has many properties similar to those of hemoglobin. It __1__ when the partial pressure of oxygen is high, and __2__ when the partial pressure is low. It is less capable of binding oxygen, however, binding 1 mol of O2 for 75,000 gm of pigment, while hemoglobin binds 4 mol O2 for 68,000 gm of hemoglobin. Unlike hemoglobin, hemocyanin is not contained __3__, and is not associated with high levels of __4__ in the blood.

1. binds oxygen 2. releases it 3. in cells 4. carbonic anhydrase

Each hemoglobin molecule can bind to __1__ molecules. The extent to which hemoglobin binds oxygen is dependent on the__2__ of oxygen in the plasma. If all the sites on the hemoglobin molecules are occupied with O2, the blood is 100% saturated and the __3__ of the blood is equal to __4__. The__4__ increases in proportion to the hemoglobin concentration. Consequently, in order to compare blood of different hemoglobin content, we use the term __5__, expressing O2 content as a percentage of O2 capacity. __6__ describe the relationship between percent saturation and the partial pressure of oxygen. The curves for all vertebrates except for cyclostomes are __7__. This is due to __8__. Oxygenation of the first heme groups facilitates the oxygenation of subsequent heme groups in the same molecule owing to conformational changes in the protein globin. The steep portion of the curve corresponds to oxygen levels at which an oxygen molecule already occupies at least one heme group, increasing the affinity of the remaining heme groups for oxygen. An important property of respiratory pigments is that they bond oxygen __9__, over a range of partial pressures normally encountered in the animal. At a low PO2 a __10__ oxygen binds to the respiratory pigment. At high PO2, however, a __11__ O2 is bound. Thus, the respiratory pigments will load O2 at the __12__, where the oxygen concentration is high, and unload O2 at the __13__, where the concentration of oxygen is low. In some animals, respiratory pigments are used as an __14__, releasing oxygen when oxygen is relatively unavailable. Seals have large amounts of myoglobin in their muscles, which releases oxygen when oxygen levels in the muscles __15__, as they do during a dive.

1. four oxygen 2. partial pressure 3. oxygen content 4. the oxygen capacity 5. percent saturation 6.Oxygen dissociation curves 7. sigmoidal in shape 8. subunit cooperativity 9. reversibly 10. small amount of 11. large amount of 12. respiratory surfaces 13. tissues 14. oxygen reservoir 15. decrease

Hemoglobin has a molecular weight of about 68,000, and contains four iron porphyrin prosthetic groups - heme - associated with the protein globin. The __1__ is made up of two equal parts each consisting of one α and one β polypeptide chain in adults; one α and one γ (fetal hemoglobin) or ε (embryonic hemoglobin) chain in the fetus. Hemoglobin will dissociate into four subunits of approximately equal weight, each containing one __2__ and one heme group. __3__ is equivalent to one hemoglobin subunit, and is a respiratory pigment that stores oxygen in the muscles. If hemoglobin is oxygenated, it is called __4__; when there is no O2 bound it is called __5__. The oxygen-binding characteristics of hemoglobins vary, and these differences are related to the structure of the globin molecule. Oxygen binding to hemoglobin does not oxidize ferrous to ferric iron. However, this reaction does occur naturally in the body, rendering hemoglobin unable to release __6__ (it increases the binding affinity between O2 and the heme group containing the ferric ion, so it is __7__ release the O2 to the tissues). __8__ is the name for this inactive form of hemoglobin. Normally, an enzyme present in the red blood cells called, __9__, reduces ferric methemoglobin to the functional ferrous hemoglobin. Certain compounds (nitrates or chlorates, for example) act to either oxidize __10__ or to inactivate __9__, thereby increasing the amount of methemoglobin and impairing oxygen transport. __11__, specifically, greatly increase the rate of oxidation of ferrous to ferric ion, overwhelming the methemoglobin reductase system. Another molecule that can inactivate the O2 carrying ability of hemoglobin is __12__. The affinity of hemoglobin for __12__ is about 200 times as great as for oxygen, and as a result, __12__ will __13__ oxygen and __14__ hemoglobin, even at very low partial pressures of __12__, causing a marked __15__ in oxygen transport to the tissues. Because of this effect, __12__ produced by incomplete combustion in car exhaust and improperly stoked wood stoves is extremely toxic. Even driving in heavy city traffic can impair brain function owing to partial anoxia.

1. globin 2. polypeptide chain 3. Myoglobin 4. oxyhemoglobin 5. deoxyhemoglobin 6. oxygen 7. unable to easily 8. Methemoglobin 9. methemoglobin reductase 10. hemoglobin 11. Nitrates 12. carbon monoxide (CO) 13. displace 14. saturate 15. reduction

Fishes such as brown bullheads are ectotherms. Therefore, warm-adapted fishes have a __1__(and express versions of enzymes that work best in warmer water) than do cold-adapted fishes of the same species. Their tissues will have a __2__ for O2, so their hemoglobin will have a __3__ O2 (when measured at their adapted temp of 24oC) than cold-adapted fishes (measured at their adapted temp of 9oC), which have a __4__. Look at the two middle lines of the curve. These differences within the same species are not accomplished by changing the hemoglobin molecule itself, but by changes in the __5__ of the red blood cells. Differences between species are usually due to differences in the __6__ of the two species.

1. higher metabolic rate 2. higher demand 3. lower affinity for 4. lower metabolic rate 5. internal environment 6. hemoglobins

Carbon dioxide diffuses into the tissues, is transported in the blood, and diffuses across the respiratory surface into the environment. Carbon dioxide reacts with water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate and carbonate ions. The proportions of CO2, HCO3-, and CO3-2 in solution are dependent on pH, temperature, and ionic strength of the solution. The ratio of CO2 to H2CO3 is about 1000: 1, and the ratio of CO2 to bicarbonate is about 1: 20. Bicarbonate is the dominant form of carbon dioxide in the blood. The carbonate content is usually negligible in birds and mammals. Carbon dioxide also reacts with -NH2 groups on proteins, and particularly hemoglobin, to form carbamino compounds. The extent of carbamino formation will depend on the number of available -NH2 groups as well as on blood pH and PCO2. The sum of all forms of CO2 in the blood - that is, molecular CO2, H2CO3, HCO3-, CO3-2, and carbamino compounds - is referred to as the total CO2 content of the blood. The CO2 content varies with PCO2, and the relationship can be represented graphically in the form of a CO2 dissociation curve. As PCO2 increases, the major change is the bicarbonate content of the blood. The formation of bicarbonate is pH dependent. A decrease in pH at constant PCO2 is associated with a fall in bicarbonate. The pH inside the red blood cells is less than that of plasma; therefore, the bicarbonate levels are lower in the red blood cells than in the plasma. Carbon dioxide is added to the blood in the tissues and removed at the respiratory surface, and the levels of CO2, HCO3-, and carbamino compounds all change during this transfer. Carbon dioxide both enters and leaves the bloodstream as molecular CO2 rather than as bicarbonate ions because CO2 molecules diffuse through membranes much more rapidly than HCO3- ions. In the tissues, CO2 enters the blood and is either hydrated to form bicarbonate or reacts with -NH2 groups of hemoglobin. The reverse process happens when the CO2 is unloaded from the blood. The CO2 hydration-dehydration reaction is slow and has an uncatalyzed time course of several seconds. In the presence of the enzyme carbonic anhydrase, found in the red blood cells, the reaction approaches equilibrium in far less than a second. Although the plasma has higher CO2 content than the red blood cells, most of the CO2 entering and leaving the plasma does so via the red blood cells. The reason for this is that carbonic anhydrase is present in the red blood cells, but not in the plasma. Therefore, bicarbonate or CO2 formation occurs much more rapidly in the red blood cell, and bicarbonate ions are subsequently transferred into or out of the plasma.

1. increases 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

The rate of oxygen uptake __1__ in proportion to the difference in __2__ across an epithelium. Hemoglobin with a __3__ for oxygen will facilitate movement of oxygen into the blood from the environment because O2 is bound to the hemoglobin at __4__. Thus, a large difference in __4__ across the respiratory epithelium - and therefore a __5__ of O2 transfer into the blood - is maintained until the hemoglobin is __6__. Only then does plasma __4__ rise. Hemoglobin with a __7__, however, will not release O2 to the tissues until the __4__ of the tissues is very __8__. In contrast, hemoglobin with __9__ will facilitate the release of O2 to the tissues. Thus, hemoglobin with __10__ facilitates uptake of O2 from the environment, while hemoglobin with __11__ facilitates the transfer of O2 to the tissues. From a functional standpoint, therefore, the ideal hemoglobin should have __12__ at the respiratory surfaces and __13__ at the tissues. This is actually effected because the hemoglobin affinity is __14__ on conditions within the red blood cells. It is reduced either by increases in __15__, temperature, and pH, for example. The __16__, or __17__, describes the effect of __18__ on the oxygen affinity. Increases in [H+] (__19__ in pH) cause a __20__ in the O2 affinity of the hemoglobin, and an __21__ in pH causes an __22__ in the O2 affinity. Increases in CO2 can affect pH by reacting with __23__ to form __24__, and by reacting with -NH2 groups on __25__ and hemoglobin to form __26__. This decrease in pH will affect the oxygen affinity of hemoglobin, causing it to __27__ oxygen more __28__. This increase in CO2 occurs in the __29__ as a result of cellular respiration. CO2 leaves the plasma at the __30__, increasing the __31__, and thus __32__ the affinity of the blood for oxygen in the lungs or gills, and __33__ oxygen loading.

1. increases 2. partial pressure 3. high affinity 4. low PO2 5. high rate 6. fully saturated 7. high oxygen affinity 8. low 9. low oxygen affinity 10. high oxygen affinity 11. low oxygen affinity 12. high O2 affinity 13. low O2 affinity 14. labile and dependent 15. PCO2 16.Bohr Effect 17. Bohr Shift 18. pH 19. decrease 20. reduction 21. increase 22. increase 23. water 24. carbonic acid 25. plasma proteins 26. carbamino compounds 27. unload 28. easily 29. tissues 30. respiratory surfaces 31. pH 32. increasing 33. increasing

High elevation animals have __1__ available to them, and thus their hemoglobin has __2__ oxygen than their relatives at lower elevations.

1. less oxygen 2. higher affinity for

Hemoglobins that have high oxygen affinities are saturated at __1__ oxygen, whereas hemoglobins with low oxygen affinities are completely saturated only at __2__ oxygen. This difference in oxygen affinity is attributed to differences in the __3__ of the globin portion of the molecule. Animals in different environments would be expected to have different needs for the ability to __4__from the environment.

1. low partial pressures of 2. relatively high partial pressures of 3. amino acid sequence 4. remove oxygen

Smaller mammals' hemoglobins have a __1__ for oxygen than larger animals. Since air-breathers have 100% saturation of hemoglobin for blood leaving the lungs at sea level, a __1__ means that the oxygen will unload in the tissues more readily. Since smaller animals have a __2__ per gram metabolic rate, they need more __3__ to their tissues.

1. lower oxygen affinity 2. higher 3. oxygen delivery

The effect of __1__ in red blood cells can explain many peculiarities about O2 dissociation curves that were confusing. The mammalian red blood cell has no nucleus, and for many years this cell was viewed as little more than an inert sac packed full of __2__. The red cell, however, has active __3__ that is not only essential to the viability of the cell, but also has a profound effect on the function of __4__. The red cell also has a high concentration of __5__ and an even higher level of __6__. The presence of these organic phosphates helps explain why a purified solution of __7__ has a much higher __8__ than whole blood (a Hb solution has a dissociation curve that lies far to the left of the curve for whole blood). If organic phosphates, particularly __6__, are added to a Hb solution, its O2 affinity is greatly __9__ and approaches that of intact cells. This __9__ is attributable to a combination of the hemoglobin with the DPG, which alters the O2 affinity. The discovery of the __6__ effect helps explain many observations that were previously puzzling. It helps explain why, if we examine whole blood, we can observe many features of dissociation curves that would be unnoted in a purified Hb solution. For example, the __6__ levels in the red blood cells of people living at high altitudes are __10__ people living near __11__. As a consequence, there is a shift to the _12_ of the O2 dissociation curve at high altitude. Thus, paradoxically a person at higher elevation will have Hb with a __13__ for O2 than a person at sea level (just the opposite as seen in llamas compared to camels). The explanation for this becomes clear when we consider that this means that the Hb will unload its O2 more __14__ at the __15__ in altitude-adapted humans than in humans adapted to sea level. During pregnancy, the amount of __6__ in the maternal red blood cells __16__, so the mother's Hb has a __17__ for O2 than normal, and can more readily __18__ O2 to the __19__ Hb. Stored blood has a __20__ for O2 than fresh blood. This occurs because as the blood ages, the amount of __6__ in the red blood cells __21__.

1. organic phosphates 2. hemoglobin 3. carbohydrate metabolism 4. O2 transport 5. ATP 6. 2,3-diphosphoglycerate (DPG) 7. hemoglobin 8. O2 affinity 9. decreased 10. greater than 11. sea level 12. right 13. lower affinity 14. readily 15. tissues 16. rises 17. lower affinity 18. give up 19. fetus 20. greater affinity 21. decreases

Respiratory pigments are made up of __1__ bound with a __2__, __3__ for hemoglobin and __4__ for hemocyanin. The binding of the respiratory pigment with oxygen greatly increases the blood's ability to transport __5__. In the absence of a __6__, the O2 content of the blood would be __7__. In humans it would be about 0.3% O2 by content. However, with hemoglobin, human arterial blood is about 20% O2 by volume. This 70-fold increase in the ability of the blood to carry oxygen is attributable to the ability of __8__ to bind __9__. In most vertebrates, the oxygen dissolved in the __10__ is a small fraction of the total oxygen transported. However, the Antarctic icefish is unique in that it lacks hemoglobin in its blood, relying entirely on the __11__ in the plasma. This lack of a respiratory pigment renders the fish transparent. It can do this because its body temperature is below 0o C (due to supercooled, highly saline water beneath the ice), and thus its metabolic rate is very low. In addition, they compensate by having an __12__ and __13__

1. protein molecules 2. metal ion 3. iron 4. copper 5. oxygen 6. respiratory pigment 7. very low 8. hemoglobin 9. oxygen 10. plasma 11. dissolved oxygen 12. increase blood volume 13. cardiac output

Fetuses need to take up oxygen from the maternal circulation. Fetal hemoglobin has a different subunit construction from adult hemoglobin, being made up of an__1__ and either an __2__ (early in development) or a __3__ (later in development). After birth, normal adult subunits of one __4__ are made, and gradually replace the fetal hemoglobin.

1. α chain 2. ε chain 3. γ chain 4. α and one β chain

Hemoglobin is red when ____ and dark maroon-red when ___; hemocyanin is blue when ____ and transparent when ____.

oxygenated deoxygenated oxygenated deoxygenated