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What is transport?
Transport = Here used as a general term to refer to all movements
Gas transport is therefore any and all movements of gas from place to place, regardless of mechanism
Which types of transport is there?
Active transport = transport against the concentration gradient
Passive transport = transport with the concentration gradient
Passive diffusion = transport with the concentration gradient over membranes
What is respiratory gases?
The principal gasses that are consumed, and produced, by cellular respiration
Oxygen (O2) and Carbon dioxide (CO2)
What does it mean with chemical potential?
Chemical potential is the strength of the tendency of a chemical substance to undergo a physical or chemical change
What is simple diffusion?
A form of diffusion that does not require the assistance of membrane proteins.
One of the principal mechanisms of respiratory gas transportation
Passive transport
What does the fundamental law of gas diffusion say?
Gases diffuse in net fashion from areas of relatively high partial pressure to those with relatively low, and this is true within gas mixtures, within aqueous solutions, and across gas-water interfaces
E.g.: an aquatic animal will only be able to get O2 from its environmental water if the partial pressure of O2 dissolved in the water is higher than the partial pressure of O2 dissolved in their blood as the blood flows through their gills
When gases diffuse in the direction of the partial pressure gradient, it doesn’t necessarily mean that it also occurs in the direction of the concentration gradient
What are some simple and special cases of diffusion?
Within a gas mixture of uniform temperature, or within an aqueous solution of uniform temperature & salinity:
If the partial pressure of a specific gas is greater in one region than in another, the concentration of the gas is also greater
Within these gas mixtures or aqueous solutions gases will therefor also diffuse from high to low concentrations when they diffuse from high to log partial pressures
What is a more complex situation in diffusion of gases?
Under more complex circumstances it’s common for gases, while obeying the fundamental laws of gas diffusion, to diffuse from low concentration to higher concentration
When is equilibrium always attained?
With respect to any given gas when partial pressure of the gas is uniform everywhere in a system
What is the equation for the rate of gas diffusion within a fluid system ( consisting of a gas phase, liquid phase or both)?
J = K(P1 – P2) / (X)
P1 = the relatively high partial pressure
P2 = the relatively low partial pressure
J = the rate of diffusion
Think of an imaginary plane that is perpendicular to the direction of diffusion between the two regions. Let ‘J’ be the net movement of gas through the plane, per unit of cross-sectional area
Directly proportional to the difference on partial pressure
Inversely proportional to the distance separating the two partial pressures (X)
X = the distance separating P1 and P2
K = a proportionality factor (Krogh diffusion coefficient)
Depends on the particular diffusing gas, the temperature, and the ease with which the gas is able to pass through the particular material separating the different partial pressures
If the two regions of interest are separated by a layer of tissue, K is termed the ‘gas permeability’ of the tissue
What is convective gas transport?
Transport by bulk flow:
Convection is the second major mechanism of respiratory gas transport
Occurs when a gas mixture or an aqueous solution flows and gas molecules in the gas or liquid are carried from place to place by the fluid form.
E.g. the transport of O2 by blood flow
Typically much faster than gas diffusion since it doesn’t depend on random molecular movements
When the animal sets fluid in motion (breathing/the pumping of blood) it costs metabolic energy. The reward for this investment is the faster transport
There are some exceptions where for example ambient winds or water currents induce internal flow within the animal
Which factor does the precise effect of fluid flow depend on?
In part on the geometry of the flow.
Two important geometries are unidirectional flow through a tube (e.g. the flow of blood through a blood vessel) and tidal flow in and out of a blind-end cavity (e.g. in the lungs of mammals)
What is rate of the convective gas transport?
CTF, where the flow is unidirectional through a tube and no gas exchange occurs through the walls
CT = the total concentration of gas in the fluid. This includes both chemically combined and free fluids
F = the rate of fluid flow
The rate of convective transport can therefore be increased by increasing the concentration or the flow rate
How have animals compensated for diffusion through liquid is slow?
Since diffusion through liquid is so slow, it can only meet transport needs over very short distances.
To solve this problem animals often employ both convective transport and diffusion.
Typically diffusion and convection alternate as the O2 makes its way through the body. The diffusion meets the needs for gas transport over short distances and convective transport over the longer ones.
What is the oxygen cascade?
A way to summarize the transport of O2 from the environment to the mitochondria of an animal
How is a oxygen cascade plotted?
To construct an oxygen cascade one plots the O2 partial pressure as successive steps along the path between an animal’s environmental source of Ch and its mitochondria (as in figure 22.8 B). The partial pressure always drops with each step because of the fact that the animals have no (known) active transport of oxygen
To better understand an oxygen cascade, what is a good comparison?
The oxygen cascade can be compared with a cascade in nature (several waterfalls in series along a stream). As seen in figure 22.8 A, only the force available at the last drop before the waterwheel (from height 4 to height 5) is able to turn it. Just as the waterwheel need a drop of a certain height to be able to turn it, the mitochondria in each cell require a certain partial pressure of O2 at the cell surface (i.e. in the capillary blood at the cell surface) to be able to receive O2 fast enough by diffusion to be able to meet their O2 needs
This is because O2 enters the mitochondria by diffusion at a rate dependent on the difference in O2 partial pressure between the blood in systemic capillaries and the mitochondria themselves
What happens in each step of the oxygen cascade?
With each step along the oxygen cascade the O2 partial pressure drops (but must always be kept high enough for O2 to diffuse to the mitochondria at an adequate rate)
What is the point of the O2-transport system in an animal?
To maintain an adequately high O2 partial pressure at cell surfaces throughout the body
What are the steps in an oxygen cascade?
First step – The transport of oxygen from the ambient air to the gas in the alveolar end sacs in the lungs
Occurs by convection
The drop in O2 partial pressure during this step is from about 0.2 atm in the ambient air to about 0.13 atm in the alveolar gas
Second step – The transport of oxygen across the alveolar sacs and through the epithelia separating the alveolar gas from the blood
Occurs by diffusion
The rate depends on the difference in O2 partial pressure between the alveolar gas and the blood
In healthy lungs a partial pressure of about 0.007 atm is sufficient to cause O2 to diffuse at the regular rate
Third step – The convective step between arterial blood and the blood in systemic blood capillaries
The arterial blood has an O2 partial pressure of about 0.12 atm and the partial pressure in the capillaries averages about 0.09 atm
Final step – The “payoff” of O2 transport: the diffusion mediated transport of O2 from the blood in systemic capillaries to the mitochondria in surrounding cells
Driven by the difference in O2 partial pressure between the blood and the mitochondria
The reason that the O2 partial pressure in the mitochondria is lower than in the capillary blood is that the mitochondria constantly draw down the partial pressure in their vicinity by chemically consuming O2, converting it to water
For aerobic catabolism to be unimpaired, the mitochondrial partial pressure cannot fall below around 0.001 atm. The capillary partial pressure therefore must be sufficiently higher than this
This is, as stated before, the key task of all the O2-tastport processes – to keep the capillary O2 partial pressure sufficiently over that of the mitochondria
How does gas phases and aqueous solution differ in their physical properties?
These are important for the physiology of the respiratory gases
How easily gases diffuse through them
Density
Viscosity
How much O2 they contain per unit of volume
Water is much denser and more viscous than air. Because of this water-breathing animals generally expend more energy than air-breathing ones to move fluid through their respiratory passage
The amount of O2 in water is dramatically lower than that of air since the water amounts depend on the solubility of O2 in water, and O2 is not particularly soluble
Warming the air lowers its absolute concentration of O2 since gases expand and become more rarefied (rarefied: definition) when they are heated
Seawater dissolves less O2 because of its salinity and warmer water dissolves less O2
The solubility of O2 decreases as temperature increases
The combination of water's higher density and lower amount of O2 leads to water being a far more difficult place to acquire O2
Water breathing animals often must work harder than air breathing ones to obtain a given quantity of air, and a greater fraction of the obtained O2 must be dedicated to obtaining more.
What is an important factor when considering the respiratory environment of animals?
The effect the organisms themselves have on their environment. Photosynthetic organisms add O2 to the environment and extract CO2 during the day and other organisms (and the photosynthetic ones during the night) remove O2 and add CO2.
The environment then exchanges O2 and CO2 with neighboring regions via diffusion and convection, equalizing the partial pressures of O2 and CO2.
What determines whether the O2 partial pressure in the portion of interest becomes different from, or remains similar to, the partial pressures in neighboring regions?
The relative strength of these processes
How does different environments differ in O2 partial pressure?
In open environments on land the composition of the air is virtually uniform from place to place. This since breezes are ubiquitous (~överallt, hela tiden) and diffusion occurs relatively rapidly in air. The differences we do see are almost always because of altitude (because the air is under less pressure)
In secluded environments on land (e.g. underground burrows) the local concentration and partial pressure of O2 is drawn down by the metabolic activities of the residents. This is possible because the convective mixing with the open atmosphere is restricted
In aquatic environments regional differences in concentration and partial pressure are far more common because the evening-out processes are less effective than in air. This means that partial pressures for example can differ from place-to-place withing a single lake
What is ram ventilation?
A type of gill ventilation observed in certain types of fish (e.g., tunas) in which the fish holds its mouth open as it swims forward, thereby using its swimming motions to drive water over its gills.
What is respiratory-exchange membrane?
A thin layer of tissue consisting typically of just one or two simple epithelia (i.e., one or two cell layers), separates the internal tissues of the animal from the environmental medium (air or water).
What does external respiration mean?
Breathing, The process by which an animal gains O2 from its environment and voids CO2 into its environment. The environment may be air (air breathing) or water (water breathing).
What does ventilation mean?
Forced flow (convection) of air or water into and out of structures used for external respiration or over body surfaces used for external respiration.
Which different types of respiratory organs are there?
Gills: In the most general sense used by physiologists, structures specialized for external respiration that project from the body into the ambient medium and are thereby surrounded by the environmental medium.
External gills: they are located on an exposed body surface and project directly into the surrounding environmental medium. Whereas external placement permits ambient water currents to flow over the gills, internal placement usually requires an animal to use metabolic energy to ventilate them.
Internal gills: Internal placement has its advantages nonetheless. When the gills are internal, the enclosing structures physically protect them and may help canalize the flow of water across the gills in ways that enhance the efficiency or control of breathing.
Branchial: Related to gills
Lungs: In the most general sense used by physiologists, structures specialized for external respiration that are invaginated into the body and thereby contain the environmental medium.
Pulmonary: related to lungs
What’s the difference between active and passive ventilation?
Active ventilation:
If the animal creates the ventilatory currents of air or water that flow to and from its gas-exchange membrane, using forces of suction or positive pressure that it generates by use of metabolic energy (as by contracting muscles or beating cilia).
Passive ventilation
If environmental air or water currents directly or indirectly induce flow to and from the gas-exchange membrane,
Which forms of active ventilation is there?
Unidirectional: if air or water is pumped over the gas-exchange membrane in a one-way path.
Tidal (bidirectional): if air or water alternately flows to and from the gas-exchange membrane via the same passages.
Nondirectional: if air or water flows across the gas-exchange membrane in many directions.
Diffusion lungs: A lung within which the air is still, so that O2 and CO2 must travel the full length of the lung passages by diffusion.
What is a dual breather?
An animal that simultaneously possesses the ability to breathe from air and from water.
What is the oxygen utilization coefficient?
In breathing, the fraction (or percentage) of the total O2 in respired air or water that is removed by the breathing process.
In circulation, the fraction of the total O2 carried by blood that is removed from the blood as it passes around the body.
What is the difference between concurrent, countercurrent and cross-current gas exchange?
Concurrent gas exchange: the medium flows along the gas-exchange membrane in the same direction as the blood.
Countercurrent gas exchange: the medium and blood flow in opposite directions
Cross-current gas exchange: In this type of exchange, the blood flow breaks up into multiple streams, each of which undergoes exchange with the medium along just part of the path followed by the medium.
What is hypoxia-inducible factors 1 and 2 (HIF-1 and HIF-2)?
A transcription factor that increases in concentration in the cytosol of a cell when the cell experiences hypoxia and that enters the nucleus, where it activates genes coding for hypoxia responses.
What is angiogenesis?
The development of new blood capillaries?
What is rhythmogenesis?
Generation of a rhythm. Usually refers to rhythm generation by neurons or sets of neurons, such as the sets of neurons that rhythmically originate nerve impulses that stimulate the breathing muscles to contract
What is the difference between continuous and intermittent breathing?
Continuous breathing: In a terrestrial vertebrate, inhaling and exhaling continuously (without significant interruptions).
Intermittent breathing: Breathing in which breaths or sets of breaths are regularly interrupted by extended periods of apnea.
Apnea: The absence of breathing.
What are the different parts of gills?
Gill slits: lateral pharyngeal openings, individual openings to gills
Operculum: In a fish, the external flap on each side of the head that covers the gills.
Gill arches: a series of paired bony "loops" that support the gills in fish.
Gill filaments: provide oxygen to their blood by taking oxygen from the water.
Secondary lamellae: is inside of gill filaments, the microscopically fine folds of tissue on the surfaces of the gill filaments that serve as the primary sites of exchange of respiratory gases between the ambient water and blood.
What is the buccal pressure pump?
The development of positive pressure within the buccal cavity of a vertebrate, used to force air into lungs or water across gills.
What is the opercular suction pump?
The development of negative pressure in the opercular cavity and sucks water from the buccal cavity into the opercular cavity.
What is the the Buccal Pressure Pump and the Opercular Suction Pump in fish?
Buccal pressure pump
A mechanism where the fish uses its mouth (buccal cavity) to generate pressure, drawing water in. When the mouth closes, the pressure forces the water over the gills, facilitating oxygen exchange. This ensures continuous water flow for respiration.
Opercular suction pump
A mechanism that aids in breathing. When the operculum (gill cover) moves outward, it creates a suction force, drawing water through the fish's mouth and across the gills, enabling oxygen exchange while keeping water flow continuous during respiration.
How does the buccal and opercular pumps work?
Stage 1: Buccal cavity refills. Expansion of the buccal cavity produces a pressure below ambient. However during stage 1 the opercular pump is in its sucking phase. The pressure in the opercular cavity is reduced to a level far below buccal pressure, and water is drawn through the gills from the buccal cavity.
Stage 2: A short transition period in which the opercular pump is completing its sucking phase and the buccal pump is beginning its pressure phase.
Stage 3: Opercular pump is in its discharge phase → pressure in the opercular cavity is elevated. Buccal pump is simultaneously in its pressure phase → buccal pressure exceeds opercular pressure → water again flows through the gills from the buccal cavity.
Stage 4: Pressure gradient in the direction favoring backflow of water through the gills. The opercular pump sucks while the buccal pump is being refilled, and the buccal pump develops positive pressure while the opercular pump is being emptied.
What is a swim bladder?
A gas-filled organ used for buoyancy in most fish, but also as an air-breathing organ in some species.
How does amphibian differ in breathing compared to fish?
Amphibians breathing: Mix water and air breathing because they move from aqutic environments to terrestrial ones.
Buccal pumping: A mechanism where air is drawn into the mouth and pumped to ventilate the gills, commonly used in amphibians with enclosed gills.
Buccopharyngeal pumping: A breathing mechanism where air is drawn into the buccal cavity and forced into the lungs by raising the buccal floor, used by amphibians.
Elastic recoil: The passive return of the lungs to their original shape after being expanded, aiding in exhalation.
How is gills of amphibian larvae different from fish?
Unlike fish, amphibian larvae develop external gills from the integument, which project into the water for gas exchange.
How is the operculum different in frogs and toads compared to fish?
An integument outgrowth forms a chamber that encloses the gills, aiding in ventilation.
What is metamorphosis?
The process by which amphibians typically lose their gills as they transition from larvae to adults.
What is unicameral lungs?
Single-chambered lungs with little internal folding, providing limited surface area for gas exchange.
What is glottis?
A muscular structure that closes after inhalation, preventing air from leaving the lungs.
Which three ways can amphibian achieve gas exchange?
Through gills, lungs and skin
Some species of frogs in temperate regions of the world hibernate at the bottoms of ponds and lakes during winter. All their O2 and CO2 exchange is then across their skin.
What does lungs do in reptiles other than birds?
Essentially take up all O2 and essentially eliminate all CO2. Skin less permeable than amphibians.
Simplest reptilian lung (most lizards and snakes) – unicameral (single chambered). Saclike with open central cavity.
Sometimes fully perfused with blood, other times well perfused in anterior end and balloon-like posterior end.
Well-perfused areas thrown into honeycomb pattern with vascularized folds to increase the area -> larger area for O2/CO2 exchange.
Air flows into the central cavity when breathing -> gas exchange with depths of honeycomb-like cells largely by diffusion.
What is multicamerial lungs?
Lugns with a major septa subdividing lung cavity into smaller parts.
Why are multicamerial lungs an advantage?
Provide a great deal more surface area for gas exchange per unit lung volume than unicameral lung, since the septa can develop highly folded gas exchange surfaces.
Appearance of cartilage-reinforced tube (bronchus) lengthwise through the lungs, allowing air to flow to all multiple chambers.
How are the lungs filled in reptiles?
During ventilation the lungs are filled by suction (aspiration) rather than buccal pressure.
Suction created by the action of thoracic and abdominal muscles; it liberated buccal cavity from its ancient functions allowing it to evolve.
Suction works in two different ways
Thoracic and abdominal expiratory muscles compress lungs to smaller volume than passive, relaxation volume during exhalation -> suction for inhalation is developed when lungs rebound elastically to larger size.
Inspiration muscles actively create suction in lungs during inhale by expanding lungs to larger size than passive, relaxation volume -> muscle activity stops and lungs rebound elastically and becoming smaller -> elastic rebound contribute to exhale. Seen in lizards and some crocodilians.
What is intercostal muscles?
Sheetlike muscles that run between adjacent ribs, the contraction of which expands or contracts the volume of the rib cage.
What is the costal suction pump?
The development of negative pressure within the thorax of an air-breathing vertebrate by action of the costal muscles between the ribs, used to suck air into the lungs.
In lizards, how does the intercostal muscles and costal suction pump work?
Lizards have well-developed ribs. Intercostal muscles run over and between ribs. These can expand and contract volume enclosed by rib cage. When lizard inhales –> intercostal muscles activate and expand rib cage – costal suction pump.
Intercostal muscles seem to help produce back-and-forth flexions when lizard is walking or running – can interfere with intercostals ability to develop ventilation forces. Some species overcome this by using buccal pressure while walking and running.
How does the mammalian airway branch?
Trachea → primary bronchi (one in each lung) → secondary bronchi → hinger-order bronchi → bronchioles → Final bronchioles end in alveolar ducts and alveolar sacs. Walls of these composed by outpocketings; each of these called alveolus, all together these form alveoli.
What is the conducting airways?
Trachea, Bronchi and all but last branches of bronchioles, everything not involved in gas exchange.
Said to constitute the anatomical dead space of the lungs. Lined with thick epithelium, not rich vascular supply.
What are the respiratory airways?
Where gas exchange between air and blood occurs.
Consists of respiratory bronchioles, alveolar ducts and alveolar sacs. Pulmonary walls of single layer of thin epithelial cells, richly supplied with blood capillaries.
What is the tidal volume?
Volume of air inhaled and exhaled per breath.
What is the expiratory reserve volume?
Max volume of air individual can expel beyond resting expiratory level.
What is the inspiratory reserve volume?
Max volume of air inhaled beyond resting inspiratory level.
What happens when mammals increase tidal volume above resting?
They use parts of inspiratory and expiratory reserve volumes.
What is vital capacity?
Max tidal volume. Attained by fully using both reserves; sum of resting tidal volume and resting inspiratory and expiratory reserve volumes.
Increase with physical activity, decrease with age and diseases.
What is the true diaphragm?
Muscular and connective tissue that separate thoracic and abdominal cavities in mammals
Contraction increases volume of thoracic cavity -> expanding lungs -> creating suction of air.
What’s the difference between internal and external intercostal muscles?
Runs between each pair of ribs.
Contraction of external -> rotate ribs outward -> expanding thoracic cavity.
Internal ones run perpendicular (vinkelrätt) with external. Contraction rotates ribs inward -> decreasing thoracic cavity.
Lungs and thoracic wall form an elastic system.
What is relaxation volume?
Volume of lungs and thoracic cavity during relaxation.
How does muscle effort differ in inhalation and exhalation?
Inhale is active, muscle effort needed. Lungs are expanded by contraction of diaphragm, external intercostal muscles and anterior internal intercostals.
Glottis not used in ordinary breathing. Exhalation passive, does not need muscle effort. Inspiratory muscles stop contraction -> lung volume return to passive state -> relaxation volume.
What happens with breathing during exercise?
During exercise tidal volume and breathing frequency increase -> additional muscle activity required.
External intercostal muscles have greater role during exercise than rest since greater expansion of rib cage is needed.
Exhalation is active during exercise breathing. Internal intercostals and muscles of abdominal wall contract and force air out of lungs. May also compress lungs beyond relaxation volume.
What is the pre-Bötzinger complex?
Pair of neuron clusters in ventrolateral medulla of brain stem, containing neurons most important for rhythmogenesis
How is a rise in CO2 partial pressure detected and what happens?
Sensation of CO2 and H+ are the most potent chemosensory controls of ventilation.
When concentration of CO2 rises, so does H+ in parallel and vice versa.
Deviation in either of these concentration from normal levels influences breathing, often exerting synergistic effects.
Ventilation increases/decreases to bring CO2 and H+ back to normal – negative feedback system.
What is carotid and aortic bodies?
Chemoreceptive bodies, outside CNS, that detect blood hypoxia.
Humans only have carotid bodies, while many other mammals have aortic bodies on their aortic branch as well.
Two carotid bodies along the carotid arteries. Receive blood flow, monitor arterial O2 partial pressure, and send signals to the brainstem via glossopharyngeal nerves.
What are mechanosensors role?
Mechanoreceptors sense stretch or tension in airways and thereby control ventilation.
Receptors send information to brain stem via sensory neurons. Signals to inhale inhibited by lung expansion and excited by lung compression. Some of these responses are known as Hering-Breuer reflexes.
What is respiratory minute volume (mL/min)
VT (mL/breath)* f(breaths/min)
VT = tidal volume
f = frequency
Both of these increase during increased metabolism. Cannot maximize both variables at the same time.
What is alveolar ventilation rate?
Rate at which new air is brought into alveoli and other respiratory airways.
(VT-VD)*f
VT = Tidal volume
VD = volume of anatomical dead space.
Fraction of all inhaled air that reaches airways: (VT-VD)/VT
What is pulmonary surfactant?
Complex mixture of metabolically produced lipids and proteins that make alveoli not behave like aqueous bubbles.
Gives alveoli dynamically variable surface tension
How do birds lungs differ from mammalian lungs?
Bird lungs have relatively large surface areas for gas exchange and thin gas-exchange membranes. The design of the bird lung, in comparison with the mammalian lung, may be an advantage at high altitude, in part because cross-current gas exchange prevails in the bird lung instead of tidal exchange.
A bird's trachea bifurcates to give rise to two primary bronchi, which enter the lungs:
What are the different parts of a birds lungs?
Mesobronchus: The primary bronchus that enters each lung passes through the lung,
Secondary bronchi: Two groups of branching arise from the mesobronchus. One group, which arises at the anterior end of the mesobronchus, spreads over the ventral surface of the lung. The other group originates toward the posterior end of the mesobronchus and spreads over the dorsolateral lung surface.
Tertiary bronchi/ parabronchi: The anterior and posterior secondary bronchi are connected by a great many small tubes, 0.5–2.0 mm in internal diameter.
The air capillaries are profusely surrounded by blood capillaries and are the sites of gas exchange.
A bird's air sacs, which are part of the breathing system, are located outside the lungs and occupy a considerable portion of the thoracic and abdominal body cavities.
What is paleopulmonal system and neopulmonal system?
Paleopulmonal system: Lung structures
Neopulmonal system: have a more or less extensively developed system of respiratory parabronchial tubes. Running directly between the posterior air sacs and the posterior parts of the mesobronchus and posterior secondary bronchi
What are the aspects of inhalation and exhalation in birds breathing?
Three aspects of the events during inhalation:
The posterior air sacs are filled with relatively fresh air coming directly from the environment.
The anterior air sacs are filled for the most part with stale gas that has passed across the respiratory exchange surfaces in the parabronchi.
Finally, the direction of ventilation of the parabronchi in the paleopulmonal system is from posterior to anterior.
Three aspects of the expiratory events:
The relatively fresh air of the posterior air sacs is directed mostly to the parabronchi.
Most of the gas that is exhaled from the lungs has passed across the respiratory exchange surfaces.
Finally, air flows through the parabronchi of the paleopulmonal system from posterior to anterior, just as it does during inhalation.
What is an air cell?
As an egg develops, it dehydrates by controlled loss of water vapor outward through the eggshell pores, a process that leads to the formation of a gas-filled space inside the egg at its blunt end.
Which are the four categories of respiratory pigments?
Hemoglobin, Hemocyanin, Hemerythrin, and Chlorocruorins.
‘’Like the hemoglobins, the other categories are groups of related compounds, not single chemical structures’’
Multisubunit structures- each molecule consists of two or more protein bonded together by noncovalent bonds
What is the oxygen equilibrium curve?
Referring to the O2-carrying properties of blood, a graph of the amount of O2 per unit of blood volume as a function of the O2 partial pressure of the blood.
A key tool for understanding the function of respiratory pigments
Can be presented in two ways
The percentage of oxygenated binding sites (Percent saturation)
Blood O2 concentration as a function of the O2 partial pressure
When is the respiratory pigment in blood of an animal saturated?
If the O2 partial pressure is high enough to for all O2 binding sites to be oxygenated.
What is percent saturation?
Percentage of binding sites that are oxygenated
What is the oxygen-carrying capacity?
The amount of O2 carried per unit of volume at saturation
What is volumes percent (vol%)?
The volume of gas carried per 100 volumes of blood
In which forms does O2 exist in blood?
Dissolved and bound to respiratory pigment
How is the O2 partial pressure affected by O2 diffusion?
In mitochondria, O2 is continually being combined with electrons and protons to from H2O O2 molecules are removed from the solution → O2 partial pressure in and around the mitochondria is lowered
Blood arriving in capillaries of systemic tissues from the lungs has high O2 partial pressure, O2 the diffuses from the blood to mitochondria → O2 partial pressure decreases → hemoglobin releases more O2 → more O2 that can diffuse to the mitochondria
What is the mixed venous blood?
The blood in the great veins leading back to the heart, formed by mixing of the venous blood coming from the various regions and organs of the body.
The O2 partial pressure of mixed venous blood represents an average of the O2 partial pressure of blood leaving the various systemic tissues
Allows us to gauge the blood’s overall drop in O2 partial pressure during circulation through all tissues combined
OBS, Does not reflect the drop in any particular tissue
A sample of this is used to calculate the yield of O2 to the systemic tissues since the blood has passed through the systemic tissues.
What are the determinants of a tissue’s venous O2 partial pressure?
Rate of blood flow through the tissue
The arterial O2 partial pressure
The amount of hemoglobin per unit of blood volume
The tissue’s rate of O2 consumption
What is the venous reserve?
The amount of O2 remaining in venous blood after the blood has passed through the systemic tissues.
What is the critical venous O2 partial pressure?
The level where if the venous O2 partial pressure is below the aerobic catabolism becomes impaired
In mammalian muscles it is approximately 1.3 kPa (10 mm Hg)
How is the binding sites of hemoglobin affected by the binding of O2?
Hemoglobin of most vertebrates have four O2 binding sites within each molecule → need for cooperativity → positive cooperativity occurs
Binding of O2 at one or two of the O2-binding sites on a molecule of blood hemoglobin alters the molecule’s conformation in ways that enhance the affinity of the remaining sites for O2, meaning that a partially oxygenated molecule is more likely than an entirely deoxygenated one to bind additional O2
During deoxygenation of a molecule that exhibits cooperativity, removal of O2 from some of the O2-binding sites tends to decrease the affinity of the remaining sites for O2, thereby promoting even further deoxygenation
What is Hill coefficient?
A measure of the degree of cooperativity among O2-binding sites in a molecule of a respiratory pigment.
How does affinity affect the respiratory pigments?
The respiratory pigments of various animals vary widely in how readily they combine with O2, a property known as their affinity for O2
Low affinity: Pigments that require relatively high O2 partial pressures for full loading and that conversely unload substantial amounts of O2 at relatively high partial pressures
High affinity: Pigments that load fully at low partial pressures and consequently also require low partial pressures for substantial unloading
What is the Bohr effect?
A decrease in the O2 affinity of a respiratory caused by a decrease in pH or an increase in CO2 partial pressure.
What is the root effect?
A decrease in the amount of O2 a respiratory pigment can bind at saturation—and thus a decrease in the oxygen-carrying capacity of blood—caused by a decrease in pH or an increase in CO2 partial pressure.
