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Circulation and Gas Exchange

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1 Circulation and Gas Exchange
Chap 42 Circulation and Gas Exchange

2 Gastrovascular cavities and body walls only two layers thick allow for easy distribution of nutrients and gas exchange

3 In insects, other arthropods, and most mollusks, blood bathes organs directly in an open circulatory system. There is no distinction between blood and interstitial fluid, collectively called hemolymph. One or more hearts pump the hemolymph into interconnected sinuses surrounding the organs, allowing exchange between hemolymph and body cells. Fig. 42.2a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

4 Blood always stays in a blood vessel - more efficient
Blood empties into sinus

5 Arteries carry blood to capillaries
The sites of chemical exchange between the blood and interstitial fluid Veins Return blood from capillaries to the heart

6 Completely separation ensures oxygenated blood going to systemic circuit under high pressure
The pulmonary and systemic circuits are not completely separated Blood going through body under low pressure

7 REPTILES (EXCEPT BIRDS) Pulmocutaneous circuit
Vertebrate circulatory systems FISHES AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS Systemic capillaries Lung capillaries Lung and skin capillaries Gill capillaries Right Left Systemic circuit Pulmocutaneous circuit Pulmonary circuit Systemic circulation Vein Atrium (A) Heart: ventricle (V) Artery Gill circulation A V Systemic aorta Right systemic aorta Figure 42.4

8 A powerful four-chambered heart
Was an essential adaptation of the endothermic way of life characteristic of mammals and birds

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10 Mammalian Circulation: The Pathway
Heart valves Dictate a one-way flow of blood through the heart

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12 Circulation movie

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14 1. Pearson circulatory Lab
Turn in Lab Quiz tommorrow 2. Heart Review Do the following review Print out quiz to turn in

15 A cardiac cycle is one complete sequence of pumping, as the heart contracts, and filling, as it relaxes and its chambers fill with blood. The contraction phase is called systole, and the relaxation phase is called diastole. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

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17 ECG Video

18 All blood vessels Are built of similar tissues
Have three similar layers Figure 42.9 Artery Vein 100 µm Arteriole Venule Connective tissue Smooth muscle Endothelium Valve Basement membrane Capillary

19 Single wall capillaries ideal for allowing diffusion through and between endothelial cells
Thicker and more elastic

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21 The apparent contradiction between observations and the law of continuity can be resolved when we recognize that the total cross-sectional area of capillaries determines flow rate in each. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

22 Speed of blood decreases in the capillaries because ?

23 What are two reasons why the pressure decreases?

24 Fluids exert a force called hydrostatic pressure against surfaces they contact, and it is that pressure that drives fluids through pipes. Fluids always flow from areas of high pressure to areas of lower pressure. Blood pressure, the hydrostatic force that blood exerts against vessel walls, is much greater in arteries than in veins and is highest in arteries when the heart contracts during ventricular systole, creating the systolic pressure. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

25 When you take your pulse by placing your fingers on your wrist, you can feel an artery bulge with each heartbeat. The surge of pressure is partly due to the narrow openings of arterioles impeding the exit of blood from the arteries, the peripheral resistance. Thus, when the heart contracts, blood enters the arteries faster than it can leave, and the vessels stretch from the pressure. The elastic walls of the arteries snap back during diastole, but the heart contracts again before enough blood has flowed into the arterioles to completely relieve pressure in the arteries, the diastolic pressure. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

26 A sphygmomanometer, an inflatable cuff attached to a pressure gauge, measures blood pressure fluctuations in the brachial artery of the arm over the cardiac cycle. The arterial blood pressure of a healthy human oscillates between about 120 mm Hg at systole and 70 mm Hg at diastole. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

27 Smooth muscles and hormones can regulate the amount of blood in capillaries
only 5-10% have blood in them at any one time

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30 The osmotic pressure due to the proteins in the blood plasma allow for about 85% of the fluids to reenter the capillaries - the remaining 15% that remain in the interstitual fluid returns via the lymph system

31 Arterial end of capillary
The difference between blood pressure and osmotic pressure Drives fluids out of capillaries at the arteriole end and into capillaries at the venule end At the arterial end of a capillary, blood pressure is greater than osmotic pressure, and fluid flows out of the capillary into the interstitial fluid. Capillary Red blood cell 15 m Tissue cell INTERSTITIAL FLUID Net fluid movement out movement in Direction of blood flow Blood pressure Osmotic pressure Inward flow Outward flow Pressure Arterial end of capillary Venule end At the venule end of a capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary. Figure 42.14

32 If the hydrostatic pressure increases there is an increases OUTFLOW of fluids into the cells

33 If hydrostatic pressure decreases there will be an Net INFLOW of material from the cells

34 Decreasing the plasma proteins lowers the osmotic pressure of the blood causing more fluid to be pushed outward

35 8. The lymphatic system returns fluid to the blood and aids in body defense
Fluids and some blood proteins that leak from the capillaries into the interstitial fluid are returned to the blood via the lymphatic system. Fluid enters this system by diffusing into tiny lymph capillaries intermingled among capillaries of the cardiovascular system. Once inside the lymphatic system, the fluid is called lymph, with a composition similar to the interstitial fluid. The lymphatic system drains into the circulatory system near the junction of the venae cavae with the right atrium.

36 Lymph vessels, like veins, have valves that prevent the backflow of fluid toward the capillaries.
Rhythmic contraction of the vessel walls help draw fluid into lymphatic capillaries. Also like veins, lymph vessels depend mainly on the movement of skeletal muscle to squeeze fluid toward the heart. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

37 Along a lymph vessels are organs called lymph nodes.
The lymph nodes filter the lymph and attack viruses and bacteria. Inside a lymph node is a honeycomb of connective tissue with spaces filled with white blood cells specialized for defense. When the body is fighting an infection, these cells multiply, and the lymph nodes become swollen. In addition to defending against infection and maintaining the volume and protein concentration of the blood, the lymphatic system transports fats from the digestive tract to the circulatory system. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

38 Filarial worms can block lymph, causing a build of up of fluid - Elephantiasis

39 Blood Composition and Function
Blood consists of several kinds of cells Suspended in a liquid matrix called plasma The cellular elements Occupy about 45% of the volume of blood

40 Plasma Blood plasma is about 90% water Among its many solutes are
Inorganic salts in the form of dissolved ions, sometimes referred to as electrolytes

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42 A negative-feedback mechanism, sensitive to the amount of oxygen reaching the tissues via the blood, controls erythrocyte production. If the tissues do not get enough oxygen, the kidney converts a plasma protein to a hormone called erythropoietin, which stimulates production of erythrocytes. If blood is delivering more oxygen than the tissues can use, the level of erythropoietin is reduced, and erythrocyte production slows. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

43 Found in bone marrow - ribs, vertebrae, breastbone, pelvis
Low O2 triggers erythropoeitin

44 At high altitudes more red blood cells are produced
Preadapted for high altitudes

45 each level results in many more molecules
Ex: thromboplastin Cascade effect: each step as as an enzyme catalyzing many more reactions at each step - each level results in many more molecules

46 LDL may increase plaque deposits - HDL may decrease
A blood clot or thrombus can result in a thromboembolus in the brain it could result in a stroke in the heart it could result in a myocardial infarction or heart attack Fatty deposits result in Atherosclerosis -more likely to catch thrombus LDL may increase plaque deposits - HDL may decrease

47 Hypertension (high blood pressure) promotes atherosclerosis and increases the risk of heart disease and stroke. According to one hypothesis, high blood pressure causes chronic damage to the endothelium that lines arteries, promoting plaque formation. Hypertension is simple to diagnose and can usually be controlled by diet, exercise, medication, or a combination of these. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

48 To some extent, the tendency to develop hypertension and atherosclerosis is inherited.
Nongenetic factors include smoking, lack of exercise, a diet rich in animal fat, and abnormally high levels of cholesterol in the blood. One measure of an individual’s cardiovascular health or risk of arterial plaques can be gauged by the ratio of low-density lipoproteins (LDLs) to high-density lipoproteins (HDLs) in the blood. LDL is associated with depositing of cholesterol in arterial plaques. HDL may reduce cholesterol deposition.

49 4 Basic Needs of Gas Exchange
1. A thin, moist respiratory surface of adequate dimension 2. A method of transport of gases to the inner cells 3. A means of protecting the fragile respiratory surface 4. A way to keep the surface moist while limiting water loss Gas exchange is needed for cell respiration

50 The part of an animal where gases are exchanged with the environment is the respiratory surface.
Movements of CO2 and O2 across the respiratory surface occurs entirely by diffusion. The rate of diffusion is proportional to the surface area across which diffusion occurs, and inversely proportional to the square of the distance through which molecules must move. Therefore, respiratory surfaces tend to be thin and have large areas, maximizing the rate of gas exchange. In addition, the respiratory surface of terrestrial and aquatic animals are moist to maintain the cell membranes and thus gases must first dissolve in water. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

51 Body surface used in gas exchange
Evaginatation increases surface area Large SA/Vol ratio gills Lungs-invaginations + circulatory system Invaginations such as trachea

52 2. Gills are respiratory adaptation of most aquatic animals
Gills are outfoldings of the body surface that are suspended in water. The total surface area of gills is often much greater than that of the rest of the body. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

53 In some invertebrates The gills have a simple shape and are distributed over much of the body (a) Sea star. The gills of a sea star are simple tubular projections of the skin. The hollow core of each gill is an extension of the coelom (body cavity). Gas exchange occurs by diffusion across the gill surfaces, and fluid in the coelom circulates in and out of the gills, aiding gas transport. The surfaces of a sea star’s tube feet also function in gas exchange. Gills Tube foot Coelom Figure 42.20a

54 Many segmented worms have flaplike gills
That extend from each segment of their body Figure 42.20b (b) Marine worm. Many polychaetes (marine worms of the phylum Annelida) have a pair of flattened appendages called parapodia on each body segment. The parapodia serve as gills and also function in crawling and swimming. Parapodia Gill

55 The gills of clams, crayfish, and many other animals
Are restricted to a local body region Figure 42.20c, d (d) Crayfish. Crayfish and other crustaceans have long, feathery gills covered by the exoskeleton. Specialized body appendages drive water over the gill surfaces. (c) Scallop. The gills of a scallop are long, flattened plates that project from the main body mass inside the hard shell. Cilia on the gills circulate water around the gill surfaces. Gills

56 Polychaete worm

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58 Water is moving countercurrent to blood flow

59 This flow pattern is countercurrent exchange.
As blood moves anteriorly in a gill capillary, it becomes more and more loaded with oxygen, but it simultaneously encounters water with even higher oxygen concentrations because it is just beginning its passage over the gills. All along the gill capillary, there is a diffusion gradient favoring the transfer of oxygen from water to blood. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

60 Tracheal systems and lungs are respiratory adaptations of terrestrial animals
As a respiratory medium, air has many advantages over water. Air has a much higher concentration of oxygen. Also, since O2 and CO2 diffuse much faster in air than in water, respiratory surfaces exposed to air do not have to be ventilated as thoroughly as gills. When a terrestrial animal does ventilate, less energy is needed because air is far lighter and much easier to pump than water and much less volume needs to be breathed to obtain an equal amount of O2. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

61 Tracheal systems in insects allow for gas to be transported directly to most cells -no need for hemoglobin to transport oxygen Spiracles control the opening the trachea

62 Fig

63 The tracheal tubes Supply O2 directly to body cells Figure 42.22b
Air sac Body cell Trachea Tracheole Tracheoles Mitochondria Myofibrils Body wall (b) This micrograph shows cross sections of tracheoles in a tiny piece of insect flight muscle (TEM). Each of the numerous mitochondria in the muscle cells lies within about 5 µm of a tracheole. Figure 42.22b 2.5 µm Air

64 Unlike branching tracheal systems, lungs are restricted to one location.
Because the respiratory surface of the lung is not in direct contact with all other parts of the body, the circulatory system transports gases between the lungs and the rest of the body. Lungs have a dense net of capillaries just under the epithelium that forms the respiratory surface. Lungs have evolved in spiders, terrestrial snails, and vertebrates.

65 Book lung found in spiders
subdivisions increase surface area

66 Increasing the subdivision of the lungs increases the surface area for gas exchange

67 Mammalian Respiratory Systems: A Closer Look
A system of branching ducts Conveys air to the lungs Branch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole Branch from the pulmonary artery (oxygen-poor blood) Alveoli Colorized SEM SEM 50 µm Heart Left lung Nasal cavity Pharynx Larynx Diaphragm Bronchiole Bronchus Right lung Trachea Esophagus Figure 42.23

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69 How an Amphibian Breathes
An amphibian such as a frog Ventilates its lungs by positive pressure breathing, which forces air down the trachea

70 How a Mammal Breathes Mammals ventilate their lungs
By negative pressure breathing, which pulls air into the lungs Air inhaled Air exhaled INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up) Diaphragm Lung Rib cage expands as rib muscles contract Rib cage gets smaller as rib muscles relax Figure 42.24

71 Higher air pressure forces air in
Lower pressure Tidal volume is a normal breath Vital capacity is the max volume of a breath Residual volume is left over after exhalation - old air that will be mixed in with the new Negative pressure breathing The volume increases by the diaphragm moving down and the rib cage moving up and out

72 The volume of air an animal inhales and exhales with each breath is called tidal volume.
It averages about 500 mL in resting humans. The maximum tidal volume during forced breathing is the vital capacity, which is about 3.4 L and 4.8 L for college-age females and males, respectively. The lungs hold more air than the vital capacity, but some air remains in the lungs, the residual volume, because the alveoli do not completely collapse. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

73 How a Bird Breathes Besides lungs, bird have eight or nine air sacs
That function as bellows that keep air flowing through the lungs INHALATION Air sacs fill EXHALATION Air sacs empty; lungs fill Anterior air sacs Trachea Lungs Posterior air sacs Air 1 mm Air tubes (parabronchi) in lung Figure 42.25 Parabronchi allow for one way flow of air through lungs

74 This system completely exchanges the air in the lungs with every breath.
Therefore, the maximum lung oxygen concentrations are higher in birds than in mammals. Partly because of this efficiency advantage, birds perform much better than mammals at high altitude. For example, while human mountaineers experience tremendous difficulty obtaining oxygen when climbing the Earth’s highest peaks, several species of birds easily fly over the same mountains during migration. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

75 High CO2 levels increase the acidity of blood and cerebrospinal fluid triggering the medulla to increase the depth and rate of breathing Low O2 levels trigger sensors in the Carotid arteries and the Aorta to trigger the medulla

76 Our breathing control centers are located in two brain regions, the medulla oblongata and the pons.
Aided by the control center in the pons, the medulla’s center sets basic breathing rhythm, triggering contraction of the diaphragm and rib muscles. A negative-feedback mechanism via stretch receptors prevents our lungs from overexpanding by inhibiting the breathing center in the medulla.

77 Concept 42.7: Respiratory pigments bind and transport gases
The metabolic demands of many organisms Require that the blood transport large quantities of O2 and CO2

78 The Role of Partial Pressure Gradients
Gases diffuse down pressure gradients In the lungs and other organs Diffusion of a gas Depends on differences in a quantity called partial pressure

79 Partial pressure of O2 is 760 mm Hg X 21%= 160

80 Oxygen Transport The respiratory pigment of almost all vertebrates
Is the protein hemoglobin, contained in the erythrocytes

81 Like all respiratory pigments
Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body One molecule of hemoglobin has 4 prosthetic heme groups, allowing it to bind to 4 O2 molecules Cooperativity -the binding of one O2 allows the next O2 to bind easier Heme group Iron atom O2 loaded in lungs O2 unloaded In tissues Polypeptide chain O2 Figure 42.28

82 Loading and unloading of O2
Depend on cooperation between the subunits of the hemoglobin molecule The binding of O2 to one subunit induces the other subunits to bind O2 with more affinity

83 Cooperative O2 binding and release
Is evident in the dissociation curve for hemoglobin A drop in pH Lowers the affinity of hemoglobin for O2

84 Bohr shifts curve to the right
H+ from carbonic acid can act as a negative modulator for hemoglobin, causing it to release more O2 Bohr shifts curve to the right At 40 mm HG pH 7.2= 60 mm Hg pH 7.4= 70 mm Hg

85 As with all proteins, hemoglobin’s conformation is sensitive to a variety of factors.
For example, a drop in pH lowers the affinity of hemo- globin for O2, an effect called the Bohr shift. Because CO2 reacts with water to form carbonic acid, an active tissue will lower the pH of its surroundings and induce hemoglobin to release more oxygen. Fig b

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87 Higher temps right shift curve making it easier to dump Oxygen

88 Animals with a high metabolic rate have a right shifted curve

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90 Hb acts as a buffer in picking up H+
Most CO2 travels in the plasma as a bicarbonate ion

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92 Bet You Didn't Know They Treat Meat With Carbon Monoxide To Fool You
Bet You Didn't Know They Treat Meat With Carbon Monoxide To Fool You. Hemoglobin has a great affinity to CO – it binds and turns red, giving even old meat the appearance of freshness. If you breath in CO, hemoglobin will not release it and not be able to transport O2.

93 Figure 42.30 Tissue cell CO2 Interstitial fluid CO2 produced CO2 transport from tissues Blood plasma within capillary Capillary wall H2O Red blood cell Hb Carbonic acid H2CO3 HCO3– H+ + Bicarbonate Hemoglobin picks up CO2 and H+ Hemoglobin releases CO2 and H+ CO2 transport to lungs Alveolar space in lung 2 1 3 4 5 6 7 8 9 10 11 To lungs Carbon dioxide produced by body tissues diffuses into the interstitial fluid and the plasma. Over 90% of the CO2 diffuses into red blood cells, leaving only 7% in the plasma as dissolved CO2. Some CO2 is picked up and transported by hemoglobin. However, most CO2 reacts with water in red blood cells, forming carbonic acid (H2CO3), a reaction catalyzed by carbonic anhydrase contained. Within red blood cells. Carbonic acid dissociates into a biocarbonate ion (HCO3–) and a hydrogen ion (H+). Hemoglobin binds most of the H+ from H2CO3 preventing the H+ from acidifying the blood and thus preventing the Bohr shift. CO2 diffuses into the alveolar space, from which it is expelled during exhalation. The reduction of CO2 concentration in the plasma drives the breakdown of H2CO3 Into CO2 and water in the red blood cells (see step 9), a reversal of the reaction that occurs in the tissues (see step 4). Most of the HCO3– diffuse into the plasma where it is carried in the bloodstream to the lungs. In the HCO3– diffuse from the plasma red blood cells, combining with H+ released from hemoglobin and forming H2CO3. Carbonic acid is converted back into CO2 and water. CO2 formed from H2CO3 is unloaded from hemoglobin and diffuses into the interstitial fluid.

94 Deep-diving air-breathers stockpile oxygen and deplete it slowly
When an air-breathing animal swims underwater, it lacks access to the normal respiratory medium. Most humans can only hold their breath for 2 to 3 minutes and swim to depths of 20 m or so. In comparison with diving mammals, humans are poorly adapted to life in the water. In 2002, free-diving champion Mandy-Rae Cruikshank set a women’s world record for static apnea of 6 minutes 13 seconds (the men’s record, set in 2001 by Scott Campbell, is 6 minutes 45 seconds) However, a variety of seals, sea turtles, and whales can stay submerged for much longer times and reach much greater depths.

95 Weddell Seal Dive Adaptations
Stores more O2 in its blood Has more blood, has larger spleen for storage of blood Has higher amount of O2 storing protein called myoglobin in muscles Heart rate(125>10) and O2 consumption rate decrease Blood to muscles restricted Blood routed to vital organs -brain, eyes /peripheral vasoconstriction.

96 A school of salema attempts to outmaneuver a hungry sea lion near the Galápagos Islands by circling to confuse the predator. Galápagos sea lions dive down some 120 feet (37 meters) on average to feed, returning to the surface after a minute or two to breathe.

97 The medulla’s control center monitors the CO2 level of the blood and regulated breathing activity appropriately. Its main cues about CO2 concentration come from slight changes in the pH of the blood and cerebrospinal fluid bathing the brain. Carbon dioxide reacts with water to form carbonic acid, which lowers the pH. When the control center registers a slight drop in pH, it increases the depth and rate of breathing, and the excess CO2 is eliminated in exhaled air.

98 The breathing center responds to a variety of nervous and chemical signals and adjusts the rate and depth of breathing to meet the changing demands of the body. However, breathing control is only effective if it is coordinated with control of the circulatory system, so that there is a good match between lung ventilation and the amount of blood flowing through alveolar capillaries. For example, during exercise, cardiac output is matched to the increased breathing rate, which enhances O2 uptake and CO2 removal as blood flows through the lungs.

99 Gases diffuse down pressure gradients in the lungs and other organs
For a gas, whether present in air or dissolved in water, diffusion depends on differences in a quantity called partial pressure, the contribution of a particular gas to the overall total. At sea level, the atmosphere exerts a total pressure of 760 mm Hg. Since the atmosphere is 21% oxygen (by volume), the partial pressure of oxygen (abbreviated PO2) is 0.21 x 760, or about 160 mm Hg. The partial pressure of CO2 is only 0.23 mm Hg. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

100 6. Respiratory pigments transport gases and help buffer the blood
The low solubility of oxygen in water is a fundamental problem for animals that rely on the circulatory systems for oxygen delivery. For example, a person exercising consumes almost 2 L of O2 per minute, but at normal body temperature and air pressure, only 4.5 mL of O2 can dissolve in a liter of blood in the lungs. If 80% of the dissolved O2 were delivered to the tissues (an unrealistically high percentage), the heart would need to pump 500 L of blood per minute - a ton every 2 minutes. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

101 In fact, most animals transport most of the O2 bound to special proteins called respiratory pigments instead of dissolved in solution. Respiratory pigments, often contained within specialized cells, circulate with the blood. The presence of respiratory pigments increases the amount of oxygen in the blood to about 200 mL of O2 per liter of blood. For our exercising individual, the cardiac output wold need to be a manageable L of blood per minute to meet the oxygen demands of the systemic system. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

102 A diversity of respiratory pigments have evolved in various animal taxa to support their normal energy metabolism. One example, hemocyanin, found in the hemolymph of arthropods and many mollusks, has copper as its oxygen-binding component, coloring the blood bluish. The respiratory pigment of almost all vertebrates is the protein hemoglobin, contained within red blood cells. Hemoglobin consists of four subunits, each with a cofactor called a heme group that has an iron atom at its center. Because iron actually binds to O2, each hemoglobin molecule can carry four molecules of O2. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

103 Like all respiratory pigments, hemoglobin must bind oxygen reversibly, loading oxygen at the lungs or gills and unloading it in other parts of the body. Loading and unloading depends on cooperation among the subunits of the hemoglobin molecule. The binding of O2 to one subunit induces the remaining subunits to change their shape slightly such that their affinity for oxygen increases. When one subunit releases O2, the other three quickly follow suit as a conformational change lowers their affinity for oxygen. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

104 Cooperative oxygen binding and release is evident in the dissociation curve for hemoglobin.
Where the dissociation curve has a steep slope, even a slight change in PO2 causes hemoglobin to load or unload a substantial amount of O2. This steep part corresponds to the range of partial pressures found in body tissues. Hemoglobin can release an O2 reserve to tissues with high metabolism. Fig a

105 In addition to oxygen transport, hemoglobin also helps transport carbon dioxide and assists in buffering blood pH. About 7% of the CO2 released by respiring cells is transported in solution. Another 23% binds to amino groups of hemoglobin. About 70% is transported as bicarbonate ions.

106 Carbon dioxide from respiring cells diffuses into the blood plasma and then into red blood cells, where some is converted to bicarbonate, assisted by the enzyme carbonic anhydrase. At the lungs, the equilibrium shifts in favor of conversion of bicarbonate to CO2. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

107 Fig

108 Fig , continued

109 Pearson Daphnia Temp Lab
Turn in Lab Quiz 2 tomorrow


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