Module 22 gas diffusion Flashcards
Where is oxygen most concentrated?
In the atmosphere (21%). Remember that gas flows down it’s concentration gradient all the way to our tissues!
What is partial pressure?
A measure of gas concentration in context of the whole environment. Or the proportion of total pressure due to the presence of one specific gas in the mixture.
160 mmHg / 760 mm Hg
The partial pressure of oxygen in the atmosphere
How do gas molecules move?
From high partial pressure to low partial pressure.
How is partial pressure different than bulk flow?
Bulk flow refers to overall movement of air but partial pressure refers to the movement of gas molecules.
What is the PO2 and PCO2 in the alveoli?
100 mmHg (O2)
40 mmHg (CO2)
What is the PO2 and PCO2 in the arterial blood?
100 mmHg (O2)
40 mmHg (CO2)
What is the PO2 and PCO2 in the venous blood?
Equal to or less than 40 mmHg (O2)
Equal to or less than 46 mmHg (CO2)
What is the PO2 and PCO2 in the venous blood at normally active tissues?
PO2 is equal to or less than 40 mmHg
PCO2 is equal to or less than 46 mmHg
How does gas exchange occur from lungs to bloodstream to tissues?
Oxygen concentrations are always lowest in the tissues so oxygen flows down the concentration gradient from lungs, to veins, to tissues. Carbon dioxide concentrations are higher in tissues, then veins, then alveoli.
Hyperventilation
when ventilation exceeds the demands of the tissues
Hypoventilation
Ventilation is low; insufficient enough to keep up with oxygen demands of tissue.
Hemoglobin
A 4 sub-unit protein consisting of iron that allows oxygen to bind to it. Found in RBC
% Hemoglobin (Hb) saturation
(O2 bound to Hb/Total O2 binding sites) * 100
Where is hemoglobin saturation the highest and where is it the lowest in the vessels?
98.5% hemoglobin saturation in the arterial blood
75% hemoglobin saturation in the venous blood (“deoxygenated”)
What is hemoglobin saturation after giving up oxygen to normal tissues?
75% and PO2 was at 40 mmHg
When muscles are active during exercise the partial pressure of oxygen CAN decrease to 20 mmHg. So hb saturation is 35%
True
Hemoglobin affinity shifts right
This means there is lower affinity for oxygen. Occurs during times of excercise. Temperature increases and pH decreases.
Hemoglobin affinity shifts to the left.
Higher affinity for oxygen
Myoglobin a protein found in muscles has a higher affinity for oxygen than hemoglobin?
True
What percentage of CO2 is dissolved in the blood?
5-6%
What percentage of carbon dioxide is bound to hemoglobin?
5-8%
Red blood cells (RBC) express an enzyme called carbonic anhydrase (CA), which catalyzes the reaction of CO2 –> bicarbonate (it also catalyzes the reverse reaction).
True!
RBC convert CO2 to bicarbonate
true
Bicarbonate exits the RBC’s and travels in the bloodstream
true
Bicarbonate is converted back into CO2 by a RBC in a lung capillary and then breathed out in the alveoli?
True
Tissues move over bicarbonate?
False they move over carbon dioxide to the RBC. RBC converts it to bicarbonate.
Hemoglobin affinity for oxygen increases when it’s cold?
True, the curve shifts to the left. Less oxygen is releases to tissues.