Flashcards in Respiratory Physiology (Part 3) Deck (104)
Describe the shape of the O2-hemoglobin dissociation curve
Percent saturation increases steeply as PO2 increases from zero to approximately 40 mmHg, and then it levels off between 50 mmHg and 100 mmHg
The shape of the steepest portion of the curve is the result of what?
a change in affinity of the heme groups for O2 as each successive O2 molecule binds, such that binding of the first molecule of O2 to a heme group increases the affinity for the second O2 moles, so on and so forth
When PO2 is 25 mmHg, percent saturation is __% and referred to as P(50)
An increase in P50 reflects a(n) ____ in affinity and a decrease in P50 reflects a(n) ____ in affinity
At the highest values of PO2 (in systemic arterial blood), the affinity of hemoglobin is ______.
At lower values of PO2 (in mixed venous blood), the affinity of hemoglobin is ______.
Alveolar air, pulmonary capillary blood, and systemic arterial blood all have a PO2 of ___ mmHg
Mixed arterial blood has a PO2 of ___ mmHg
A PO2 of 40 mmHg corresponds to approximately __% saturation and a ____ affinity of hemoglobin for O2. What is the significance of this?
These changes n affinity facilitate loading of O2 in the lungs (where PO2 and affinity are highest) and unloading of O2 in the tissues (where PO2 and affinity are lower).
In the lungs, hemoglobin is __% saturated because affinity is _____.
In the tissues, hemoglobin is __% saturated because affinity is _____.
Shifts of the O2-hemoglobin dissociation curve reflect what?
changes in the affinity of hemoglobin for O2
Shifts of the O2-hemoglobin dissociation curve produce changes in what?
When does the O2-hemoglobin dissociation curve shift to the right?
When there is a decreased affinity of hemoglobin for O2
A decreased affinity of hemoglobin for O2 is reflected in a(n) ____ P50. What does this mean?
This means that 50% saturation is achieved at higher-than-normal value of PO2
When the affinity decreases, unloading of O2 in the tissues is _______.
What 4 things cause a decrease in affinity and a right shift in the O2-hemoglobin dissociation curve?
- increases in PCO2
- decreases in pH
- increases in temperature
- increases in 2,3-DPG concentration
The effect of PCO2 and pH on the 02-hemoglobin dissociation curve is called the ____ effect
An increase in temperature shifts the curve to the right which does what?
provides more O2 to the tissue
Under what conditions does 2,3-DPG concentration increase?
under hypoxic conditions, such as living at high altitude
When does the O2-hemoglobin dissociation curve shift to the left?
When there is an increased affinity of hemoglobin for O2
An increased affinity of hemoglobin for O2 is reflected in a(n) ____ P50. What does this mean?
This means that 50% saturation occurs at a lower-than normal value of PO2
When the affinity increases, unloading of O2 in the tissues is _______. Why?
binding is tighter
What 4 things cause an increase in affinity and a left shift in the O2-hemoglobin dissociation curve?
- decreases in PCO2
- increases in pH
- decreases in temperature
- decreases in 2,3-DPG concentration
Describe why the presence of hemoglobin F causes a shift to the left
The binding of 2,3-DPG does not bind as avidly to the gamma chains of the hemoglobin F as it does to the beta chains of hemoglobin A. This results in increased O2 affinity
Why is this increase in affinity beneficial to the fetus?
Their Pa(O2) levels are low (approximately 40 mmHg)
Carbon monoxide _______ the amount of O2 bound to hemoglobin
CO binds to hemoglobin with an affinity that is ___ times that of O2 to form what?
What is the siginificance of CO having a much higher affinity to hemoglobin that O2?
The heme groups that are bound to CO decrease the number of O2-binding sites available on the hemoglobin. This means that the O2 content of blood and the delivery to tissues decreases dramatically