Respiration: Oxygen Transport Flashcards
oxygen transport cascade (5)
- ventilation (air)
- pulmonary diffusion (lungs)
- circulatory diffusion (blood)
- muscle diffusion (capillaries)
- muscle utilization (tissues)
how does PO2 and PCO2 change from the environment to the tissues (2)
- PO2 decreases from environment to the tissues
- PCO2 decreases from the tissue to the environment
solubility of O2 in aqueous fluids
- low
metalloproteins/respiratory pigments
- proteins containing metal ions which reversibly bind to oxygen
how do respiratory pigments affect oxygen carrying capacity
- increase O2 carrying capacity by 50-fold
respiratory pigments: types (3)
- hemocyanins
- hemerythrins
- hemoglobins
respiratory pigments: hemocyanins
- organisms
- metal type
- location
- appearance
- arthropods and molluscs
- contain copper
- usually dissolved in hemolymph
- appears blue when oxygenated
respiratory pigments: hemerythrins
- organisms
- metal type
- location
- appearance
- worm-like organisms and sea clams
- contains iron directly bound to protein
- usually found inside coelomic cells
- appears violet-pink when oxygenated
respiratory pigments: hemoglobin
- organisms
- metal type
- location
- appearance
- vertebrates, nematodes, crustaceans, insects
- globin protein bound to heme molecule containing iron
- encapsulated in RBCs
- appears bright red when oxygenated
hemoglobin structure (2)
- structure (2)
- mutations
- often 2 alpha and 2 beta chains
- each chain is ~145 amino acids
- single aa substitutions can have profound effects on function
myoglobulin
- type of hemoglobin found in muscles
what percentage of blood are RBCs
- 30-60% of blood consists of RBCs
Hb and RBCs
- RBCs encapsulate Hb and transport O2 and CO2
- allows for fine-tuning of micro-environment around Hb to optimize function
what is the percentage of physically dissolved O2 and O2 bound to Hb in blood (2)
- 1.5% of O2 is physically dissolved
- 98.5% of O2 is bound to Hb
oxygen equilibrium curve (OEC)
- compares percent saturation of hemoglobin with PO2
OEC: shape (2)
- sigmoid shape
- allows for maximal unloading with a small change in PO2
OEC: maximal unloading (2)
- occurs at 50% O2 saturation of Hb (P50)
- animals alter P50 of hemoglobin to optimize O2 loading and unloading
how does the circulatory system respond to O2 stress (exercise, hypoxia, diving) (2)
- RBCs are released from the spleen
- elevates hematocrit and hemoglobin levels
releasing additional RBCs from spleen: advantage (2)
- enhance oxygen uptake and delivery
- increase O2 carrying capacity in blood
releasing additional RBCs from spleed: disadvantage
- viscosity of blood will eventually be too high, decreasing flow of blood
hemoglobin molecule stages (3)
- T state
- R state
- Hb molecule goes from T state to R state as it is oxygenated
Hb: T state (2)
- tense state
- oxygenation of the Hb is difficult
Hb: R state (2)
- relaxed state
- O2 can be added to the Hb more easily
T –> R state transition (2)
- transition is associated with weakening/breaking of salt bridges within Hb molecule
- binding of each additional O2 induces a conformational change that relaxes Hb further
what are the ideal OEC conditions at the gas exchange surface (2)
- high Hb affinity (low P50) maximizes O2 uptake
- left-shifted OEC
what is the ideal OEC conditions at the tissues (2)
- low affinity Hb (high P50) maximizes tissue O2 delivery
- right-shifted OEC
how does “right shifting” the OEC affect respiration (2)
- P50 is increased
- facilitates O2 delivery to active tissues producing CO2
how does “left shifting” the OEC affect respiration
- P50 is decreased
- facilitates O2 uptake at the respiratory surface
what are conditions that affect OEC (5)
- pH
- PCO2
- temperature
- organic phosphates
- amino acid sequences
OEC: pH changes
- decreasing pH reduces O2 affinity by stabilizing the “T state” and right-shifting the OEC
OEC: PCO2 changes
- increased PCO2 reduces oxygen affinity by stabilizing the “T state” and right shifting the OEC
OEC: temperature changes
- increase in temperature decreases oxygen affinity by stabilizing “T state” and “right shifting” the OEC
what is an advantage of temperature changes in OEC
- promotes oxygen delivery to warm muscles during exercise
OEC: organic phosphates (3)
- ATP, GTP, 2,3-DPG
- increase in [ ] decreases oxygen affinity by stabilizing “T state” and right-shifting the OEC
- important for fine-tuning blood P50
organic phosphate: mammals
- 2,3-DPG
organic phosphate: birds
- IP5
organic phosphate: reptiles, amphibians, fish
- ATP or GTP
when are organic phosphate levels modified (2)
- during exposure to hypoxia
- during development altering Hb-O2 affinity
what therapeutic applications do organic phosphates have (2)
- synthesis makes it difficult to make artificial blood
- important in extending life of blood and blood banks from days to months
OEC: amino acid sequences
- specific amino acid substitutions have large effects on overall blood oxygen affinity
fetal Hb (2)
- generally possess blood O2 affinity that is higher than maternal form
- allows fetus to get O2 from maternal blood
what does the amount of O2 stored in the blood depend on (2)
- PO2 of the plasma
- Hb - oxygen affinity
PO2 of the plasma (2)
- amount of “pressure” that oxygen can bring to bear on the system; how much O2 is “trying” to be loaded
- only dissolved O2 contributes to partial pressure, while bound O2 does not
Hb – oxygen affinity
- the affinity of the carrier (Hb) to carry oxygen in any particular set of circumstances
what occurs at P50 (2)
- lots of O2 unloading within small change in PO2
- O2 physically dissolved leaves first, and Hb bound O2 replaces the dissolved O2
what occurs to drop P100 to P50
- oxygen “release” during arterial-venous blood transit before entering site of tissues
why is so little O2 released before P50
- at 40-100 Torr, Hb has high affinity for O2 and does not “want to” release it
Fick equation for O2 delivery
MO2 = Q x (CaO2 - CvO2)
Fick equation for O2 delivery: Q
- cardiac output
Fick equation for O2 delivery: CaO2 - CvO2
- O2 content of arterial and venous blood
root effect (3)
- describes how bony fishes (teleosts) exhibit reduction in O2 carrying capacity with increase in CO2 or reduction in pH
- due to dramatic stabilization of “T state”
- this acidified blood won’t reach 100 carrying capacity, no matter how high the PO2 is
Bohr effect
- Hb oxygen binding affinity is inversely related both to acidity and to the concentration of carbon dioxide
swim bladder (4)
- many bony fish have swim bladders that help to maintain neutral buoyancy
- gas-filled sac
- increase gas to increase buoyancy and remove gas to decrease buoyancy
- in most species, the gas used is O2
how do fish fill their swim bladder with O2 (2)
- gulp of air
- O2 excreted from blood
depth and pressure in water
- in water, every 10m of depth is an additional 1 atm of pressure
swim bladder: gulp of air
- physostomus
swim bladder: O2 excreted from the blood (2)
- physoclistus
- utilize Root effect, gas gland, and countercurrent exchange
what is the basic mechanism of O2 addition to the swim bladder (2)
- arterial blood experiences localized acidosis from gas gland production of H+ and CO2
- “T state” becomes stabilized and drives O2 from Hb, elevating the PO2
- excess O2 diffuses and inflates the swimbladder lumen
how does the rete mirable contribute to swim bladder inflation (2)
- consists of countercurrent arterial and venous capillaries, in close proximity
- CO2 from venous blood diffuses into arterial blood, contributing to localized acidosis and increase in PO2
what is the result of the gas bland and rete mirable on the swim bladder (2)
- PO2 can be up to 30,000 mmHg
- swim-bladder can inflate with pure O2 at great depths
where else can localized acidosis, similar to filling the swim bladder, be found? (2)
- similar structure exists in fish eyes
- ensures oxygen delivery to this structure to improve ability to see
catastrophic decompression (2)
- fish are brought up from great depths to quickly
- swim bladders rapidly expand due to decrease in pressure
how is carbon monoxide (CO) produced
- byproduct of combustion
carbon monoxide (CO) and Hb: affinity (2)
- CO binds Hb with affinity 250x higher than O2
- Hb becomes 100% saturated with CO at PCO = 0.6 mmHg
how does CO affect O2 in blood (3)
- CO competes with O2 for binding to Hb
- decreases effective O2 carrying capacity of blood
- small [CO] has large effects on the system
0-10% CO-Hb symptoms
- no symptoms
10-25% CO-Hb symptoms (2)
- headache
- nausea
30-35% CO-Hb symptoms (4)
- drowsiness
- headache
- nausea
- vomiting
40% CO-Hb symptoms
- collapse
45% CO-Hb symptoms
- brain damage
50% CO-Hb symptoms
- death
