Biol 224 Lecture 24: Gas pick up and delivery

Nitrogen transport

transported in blood as dissolved gas

• no physiological function transported in plasma and dissolved

Does high pressure make it easier or harder for gas molecules to dissolve in blood?

Makes it easier

O2 and CO2 transport

dissolved gas levels in plasma insufficient to meet needs of tissues

RBCS provide transport mechanisms for both O2 and CO2

How much of Co2 can be disssolved in plasma?

7%

Oxygen transport

carried mainly by RBCs bound to hemoglobin

How many heme oxygen binding sites per Hb molecule?

4

Saturation percentage

Number of sites occupied by oxygen (Hb)

complete saturation is 4 = 100%

normal range is 95-100%

Hemoglobin

oxygen binding, weak bonds oxygen easily dissociates

Dissociation rates dependent upon

Po2, pH and temperature

Rate of dissociation

How fast the oxygen comes off

What does rate of dissociation depend on?

What tissues are doing

ex: if you’re excersising partial pressure of O2 is going down becasue you are using more O2

pH in cells go down because its using more oxygen producing more Co2 

increases dissociation

Partial pressure of O2 (Po2)

alveolar levels of 100mHg gives 97.5% hemoglobin saturation 

Alveolar of 60mmHg gives 90% (don’t want to go below 90) (high altitudes/compromised pulmonary ventilation) 

Po2 at tissue levels

40mmHg hemoglobin saturation is 75%

active tissue levels of 20 mmHg hemoglobin saturation is 35 %

Oxyhemoglobin graph

Po2 as tissue becomes more active

levels of Po2 decrease (you’re using more oxygen to make ATP)

pH level as tissue becomes more active

More acidity

Temperature as tissue becomes more active

temperature increases

Carbon dioxide transport

70% in RBC is carried as bicarbonate ions HCO3-

bicarbonate is extremely soluble (baking soda in water)

Carbonic anhydrase enzyme in RBC

CO2 + H2O → carbonic acid (H2Co3)

Carbonic acid dissociates into bicarbonate ion and hydrogen ion 

affects blood pH levels 

How much Co2 is bound to hemoglobin

23% called carbaminohemoglobin → binds to protein 

Draw CO2 cycle

CO2 and O2 Transport Draw