Transport Of Gases Flashcards
What % of oxygen is carried bound to Hb from the alveoli to the tissues down pp
98% (2% is dissolved in plasma)
How many oxygens bind to the heme groups (fe and porphyrin)
4 = hb4o2
Which 4 things affect Hb saturation
Ph
Co2
Temp
23 BPG
What saturation do Hb have at high pp02 (100 in the alveoli)
97.5%
What happens to saturation at tissues with ppo2 which is low (40 at rest)
20-35% dissociation
The Hb is much less saturated at around 70% at low ppo2
Tissues which are respiring / exercise have lower than 40mmhg po2, what happens to dissociation/ saturation
85% of the oxygen becomes dissociated from Hb
Delivers o2 to the tissues
Why is ph / co2 high in the tissues which affects dissociation
Tissues are respiring producing co2 which is then converted to H to decrease ph
What happens if there is high pco2 eg at the tissues
Saturation decreases
Faster dissociation of o2 from the Hb
What would a lower ph (H+ presence due to co2) cause
Faster dissociation of o2 from Hb
ensures o2 to respiring tissues
Explain the steps of how co2 diffusion into rbc at high pco2 eg at tissues causes oxygen dissociation
Co2 presence will react with h20
Forms H2co3 (carbonic acid) - VIA CARBONIX ANHYDRASE
this splits into H+ and HCO
H+ binds to Hb to form HHb
This displaces o2 and o2 can diffuse into tissues
How does H binding to Hb cause oxygen dissociation
Hb becomes in the Taut state at high pco2 / H
This causes dissociation of oxygen to tissues
What is the effect of co2 and H called on oxygen dissociation
Bohr effect
What happens to the Hco3 produced by co2 diffusion into rbc at high pco2 levels
Diffuses into the blood/ plasma
When does temp increase
During exercise
How does temp affect dissociation
Increased temp due to exercise increases dissociation of o2 to tissues
How does 2,3 DPG affect dissociation
High 2,3 DPG causes faster dissociation
How does dpg cause dissociation
Interacts with B chains and causes 02 dissociation
When would high dpg be needed
In people with hypoxia / low o2
Increases their dissociation
Eg anemia, at high altitudes (low po2)
How is Hbf different in dissociation
Much higher affinity/ saturation at every po2 than normal maternal dissociation curve
What happens in anemia to cause low o2 levels
They have small / non working rbc with low o2 capacity
Even if saturated
Always much lower o2 content
Does dpg cause dissociation in foetal hbf?
No
How much of co2 is dissolved in plasma from tissues
7%
Other than dissolved co2, how else is co2 transported to alveoli
As HCO3 (70%)
Or
As Hb co2 (carbaminohaemoglobin) (23%)
How is Hco3 produced and then transported to alveoli (bicarbonate)
Co2 diffuses into rbc from tissues
Reacts with h20 to form H2co3
Splits into H and Hco3
H binds onto the HHb whereas Hco3 diffuses into plasma to be transported
How is co2 later diffuses into alveoli
The 70% Hco3 binds with the H from HHb to form H2co3 (carbonic acid)
H2co3 converts to co2 and water and co2 diffuses into alveoli
Some co2 also from the dissociation of 23% hb co2 (carbamino haemoglobin)
7% diffused co2 diffuses straight to alveoli
At high pco2 what happens to carbonic anhydrase action
Converts the co2 and water to H2co3 forming Hco3 70%
Why would Hbco2 cause o2 dissociation as well as HHb would
Because it also favours the T state
Why does the production of co2 ie from HCO and H or the opposite reaction be slower in plasma than in RBC
No carbonic anhydrase to convert carbonic acid into co2 and water
What does CO bind to to stop o2 dissociation
Fe
How does CO stop oxygen dissociation
Shifts it to the Relaxed state (high saturation)
Why does co Hb have lower saturation
Rbc can’t pick up as much 02
How can CO poisoning be treated
Oxygen hyperbaric therapy
Why is NO binding to rbc important
Causes smooth muscle dilation to allow 02 dissociation to tissues
How does NO bind
Bind to oxygenated
Or to Fe of deoxygenated rbc
