Flashcards in Respiration 6 Deck (13)
How is o2 transported in blood?
1. Dissolved in plasma 2%
a. Happens first
2. Bound hemoglobin 98%
a. Happens second
02 is pretty insoluble.
Only soluble portion (2%) is NOT enough
Hemoglobin is very important.
What is the content of oxygen in the blood?
Total 02 in blood (dissolved and chemically bound)
- 20 vs 15 in artieral vs venous
5ml/100ml diffuses into the tissues.
Requreis partial pressure difference.
How is oxygen transported?
Hemoglobin (Hb) combines rapidly and reversibly (allows it to be released to tissues)
Deoxyhemooglobin and Oxyhemoglobin
HB changes colour if its got 02 on it
Whats a pulse oximeter?
Measures oxygen saturation
Saturation: how much blood is bound to hemoglobin.
SHines 2 light beams through translucent part of body to estimate Sa02
Normal range: 95-100%
Does O2Hb participate in diffusion?
No it stays in teh blood. 02 first difusses across membrane as long as the P02 (partial pressure gradnet) exists. THe HB acts as a sink and will take up oxygen until it is fully saturated and partial pressures go to equilibrium.
Describe the oxyhemoglobin dissociation curve.
Loading O2 at the lungs.
Mixed venous blood at po2:40 enters pulmonary capillary, equilibrate with alveolar air to po2 100 reaching 98% saturation before leaving lung s
Plateau at 60-100 PO2 is a SAFETY margin for when lung PO2 is low (disease/high altitude)
Increasing PO2 above 100 doesn't improve oxygen saturation. Ceiling effect.
Binding to hemoglobin depends on partial pressure.
THe more partial pressure the more saturation of HB
Unloading at tissue sites
Arterial blood reaches tissues, Po2 falls from 100-40 as it unbinds.
- once a little unbinds and diffuses, a LOT FOLLOWS kinda like a cascade. this is the STEEP REGION.
- tissue po2 depends on metabolic acvitity. Lower po2 means a lot of unbinding of hemoglobin.
Is the position of the dissociation curve fixed?
NO it changes with affinity of Hb for O2.
Normally: partial pressure at 50% saturation is around 27 mmHG
Left shift: increase affinity, partial pressure needs to be lower to reach saturation
Right shift: decrease affinity: partial pressure needs to be higher to reach saturation (easy to unbind oxygen)
What causes right/left shifts in a dissociation curve?
Exercise: R shift (hot, produces c02 (acidic)
Hypothermia (L shift, greater affinity for 02)
2,3 BPG (RBC glycolysys, increase hyopxia, disease, heart failure)
Fetal HB (higher for 02, L shifted, favour materal to fetal blood)
To move right: increase temp, DPG, and PC02, decrease PH
CO2 and H and O2 cause conformational changes on hemoglobin affecting its carrying abilities.
Bohr dudes discoverd this
What is the impact of anemia and CO on the oxyhemoglobin dissociation curve?
Anemia: less hb, less 02 carrying cabacity, less 02 in blood. but SATURATION remains normal. (always 4/4, but not actually enough O2)
CO: competes for 02 binding sites, reduce hemoglobin content. L shift. Hard for 02 to unbind at tissues. Tissue hypoxia.
Describe transport of co2 in blood.
physically dissolved 7% in blood (more soluble than oxygen)
physically disolved as bicarbonate Hco3 (70%)
chemically bound to HB molecule (23%)
total conent in artiral blood (48%)
total content in venous blood: 52.
- more soluble in plama.
4ml/100ml each circulation is taken out.
Describe the role of carbonic anhydrase.
Assists in binding co2 in the red blood cell. Co2 binds water to become carbonic acid H2CO3 (made by carbonic anhydrase) -accelerates this by 1000 fold.
- when co2 enters RBC because of diffusion, it either becomes
1. bound to hemoglobin as carboaminohemoglobin
2. binds to h20 to become carbonic acid H2co3 then this makes the area acidic,
2.1 carbonic acid becomes bicarbonate and H ion
3. the acidic hydrogen binds oxyhemoglobin causing pH change and oxy unbinds
4. when oxy unbinds it goes down its diffusion gradient to the tissues
5. freeing up sites at hemoglobin for co2 . H + Hb + Ho2 = carboaminohemoglobin.
1. Get rid of it as bicarbonate
2. Get rid of it by attaching it to hemoglobin (no more partial pressure, it’s a SINK) to maintain driving partial pressure gradient to allow co2 to come out of tissue in bicarbonate and carbinimo form.
Describe the carbon dioxide disocciation curve.
Almost Linear: not sino like oxygen.
Curve depends on oxygenation of Hb
Co2 transport in blood depends on 02 release from Hb.
HALDANE EFFECT: depends on 02 release from hemoglobin
High o2, less co2 content
LOW o2, blood can carry more co2
At any partial pressure