Lecture 32: O2 and CO2 Transport Flashcards
Two forms in which O2 is carried in the body
- Dissolved
2. O2 combo with hemoglobin
Dissolved O2 percentage
2%
Form of O2 that produces partial pressure and drives O2 diffusion
dissolved
Does O2 bound to hemoglobin contribute to partial pressure in blood?
Nope
When Hb is saturated, blood PO2 rapidly
equalizes with alveolar PO2
Hb facilitates a large net transfer of O2 by
acting as a storage depot to keep PO2 low
% saturation of hemoglobin is a function of
the PO2 of the blood
Binding of O2 to Hb is cooperate, meaning
- The binding of each O2 makes it easier for the next O2 to bind
- This steepens the O2-Hemoglobin Dissociation curve
O2 hemoglobin dissociation curve flattens when
Between 60 and 100mmHg as all binding sites become occupied. Occurs in the lungs
In a resting individual, the normal PO2 leaving the tissue capillaries of skeletal muscle is about __ mmHg and approx. ___% saturated, meaning…
40
75
some O2 bound to Hb is released into the blood and can diffuse into the tissue
During conditions of vigorous exercise, the blood PO2 can decline to levels as low as ___ mmHg because
20
skeletal muscle cells are using O2 in aerobic respiration
At PO2 of 20 mmHg, approx. ____% of Hb is saturated with O2. Thus
35%
Hb releases a large amount of O2 to active cells
When O2 needs of tissues increase, the blood Po2
decreases
P50
- PO2 when Hb is 50% saturated
- Approx 25-35 mmHg
- Used as an indicator for a change in affinity of Hb for O2
Effect of CO2 on binding of HB and O2 - increase in metabolic activity in tissues
- Increase in CO2
- Increase in H+
- Decreased affinity for O2
- Shift of O2 hemoglobin curve to the right
Consequence of increased P50
-Hemoglobin unloads O2 to the tissues
Bohr effect
The effect of PCO2 and pH on the O2-Hemoglobin association curve
Effect of CO2 on binding of Hb and O2 - decrease in metabolic activity in the tissue
- Decrease in CO2 production
- Decrease in H+
- Left shift of O2 Hb dissociation curve
Therefore, when the demand for O2 is more tightly bound to hB and less O2 is delivered to tissues
Heat is produced by working muscle and the O2 hb dissociation curve shifts to the
right, providing more O2 to the tissues
When heat is produced, P50
increases which suggests a decreased affinity of Hb for O2
2,3 - diphosphoglycerate
- By product of glycolysis in rbc
- Binds reversibly with Hb and reduces affinity for O2
- Shifts O2-Hb curve to right
Production of 2,3 BPG increases under
hypoxic conditions
Anemia effect on 2,3 BPG production
Increases production of 2,3 - BPG by rbc to facilitate the delivery of O2 to tissues
P50 increases
PCO2, temp, and 2,3 - BPG effect of O2 HB curve
right shift wiith no change in O2 binding capacity
CO effect on O2 Hb curve
Causes a left shift of O2 - Hb curve
Decreases O2 binding capacity
Co binds to Hb with an affinity that is ___ times greater than O2
250
CO + Hb =
Carboxyhemoglobin (COHb)
CO reduces O2 binding by ___ %
50%
O2 -binding sites not bound to CO have an ____ affinity for O2, thus
increased
P50 decreases, making it more difficult for O2 to be unloaded in the tissues
Three forms of Co2 in the blood
- Dissolved Co2
- Carbaminohemoglobin
- Bicarbonate (HCO3-)
Dissolved Co2 depends on the
PCO2
What percentage of CO2 is dissolved
10%
Carbaminohemoglobin
- CO2 binds with globin portion of hemoglobin
- Reduced Hb has a greater affinity for CO2 than HBO
- Unloading of O2 from Hb in tissue capillaries facilitates picking up of CO2 by Hb
What percentage of CO2 is carbaminohemoglobin
23%
Greatest percentage of CO2 (___) is in what form
70%, Bicarbonate
In the lungs, HCO3-
is reconverted to CO2 and expired
The direction of the carbonic acid reaction depends mostly on
CO2
Where are H+ and HCO-3 formed
In tissue capillaries
Haldane effect
- Hemoglobin that has released its O2 binds more readily to CO2 than Hb that has O2 bound to it
- Removal of O2 from Hb increases the ability of Hb to pick up CO2 and CO2- generated H+
- An increase in O2 released from Hb = an incres in CO2 and H+ uptake by hemoglobin
At the lungs, CO2 dissolved in plasma
diffuses into the alveoli and is exhaled
When blood reaches the pulmonary capillaries,
- deoxyhemoglobin is converted to oxyhemoglobin
- since oxyhemoglobin has a lower affinity for H+ than deoxy, H+ are released within rbc
- Attracts HCO3- from the plasma, which combines with H+ to form carbonic acid
Under conditions of lower PCO2, as occurs in the pulmonary capillaries,
carbonic anhydrase catalyzes the conversion of carbonic acid to carbon dioxide and water
