Transport of O2 and CO2

transport of O2

two forms:

• dissolved: poorly in plasma, proportional to PO2, tiny amount

• bound to hb: hb can bind 4 O2 molecules, O2 can bind and unbind

as PO2 increases, O2 bound to hemoglobin ?

increases, not linearly:

• increases affinity for O2 for hb, making it easier for next O2

• as O2 is removed, decreases affinity for O2, more O2 is removed

at PO2 of 100 mmHg

hemoglobin is saturated: 100%

dissolved O2 does what?

• defines PO2: dissolved O2 and PO2 are same

• detected by chemoreceptors: o2 bound to hb cannot be detected

• used by cells

• PO2 in lungs and hb

• PO2 at 60 mmhg

• PO2 past tissues

• PO2 near active tissues

• PO2 = 100 mmhg, hb = 100% satyrated

• Po2: nearly 100% due to safety factor for hb saturation

• PO2: 40 mmhg: Hb is 75% saturated, so 25% is removed near tissue

• PO2: 25 mmHg: near active tissues, hb 50% saturated, so 50% removed, steep region of curve: makes it easier to remove next O2

Bohr effect on O2-Hb equilibrium: shift right and left

• both Co2 and H+ bind to hb

• Shift left: occurs in lungs: makes it easier to add O2 and Hb blood flows thru

  • decreased H+, CO2, temperature, DPG

• Shift right: increased H+, CO2, temp, DPG (BPG): near active tissues, easier to remove O2

  • H+, CO2, temp, all produced by active tissue

  • DPG produced by RBC, release is stim by hypoxia and excercise

Hypoxia: what two condition: decreases PO2? What happens/

• Diffusion impairment: edema in lungs

• Decreased atmospheric Po2: high altitude

• What happens

  • decreased Po2 found in arterial blood, decreased dissolved PO2 is detected by chemoreceptors and stim breathing

What two conditions have still normal PO2 in blood? what happens?

• anemia (not enough RBC): less hb, less O2 bound to hb

• CO poisioning: CO bound to hb, less O2 bound to hb

• what happens

  • not detected by chemoreceptors, decreased O2 content in blood, when the dissolved O2 is used, no O2 to remove from Hb to replace it

Transport of CO2

• dissolved in plasma 10% (more than O2)

• Bound to proteins - mainly hb (30%)

• Bicarbonate ions: 60%:

  • carbonic anhydrase: enzyme needed ot convert CO2 to HCO3: found in RBC

60% of CO2 is converted into HCO3 and H+ →

the H+ binds to Hb, the HCO3 leaves the rbc to enter plasma in exchange with Cl- (cl-shift, rbc becomes loaded with Cl- as it passes by tissue)

Haldane effect

• when O2 binds to hb, less CO2 binds to hb

• occurs in lungs: O2 diffuses into the blood → binds to Hb → less CO2 bound to hb → CO2 expired

• Bohr effect is opposite: it occurs near active tissue: when there are high levels of CO2 binding to Hb so there is less O2 bound to hb