02a: Ventilation and Diffusion Flashcards
Diffusion becomes the dominant mechanism of gas transport (before/beyond) which point in respiratory tree?
Beyond terminal bronchioles
Bulk flow: gas movement results from differences in (X). How does this differ from diffusion?
X = total pressure (i.e. total pressure gradient)
Diffusion: certain gas moves down its own partial pressure gradient
Linear velocity of flow is (high/low) in upper airways and (increases/decreases) as it approaches alveolar ducts due to increase in (X).
High;
decreases;
X = cross-sectional area (by nearly 5,000 fold)
T/F: Bulk flow essentially ceases in respiratory zone.
False - volume change seen in alveoli
Deposition of particulates in alveoli occurs as result of (X). How does the body take care of this?
X = low gas velocity
Macrophages remove the particulates
T/F: Diffusion in any lung is not rate-limiting.
False - in normal lung, but diffusion may be limited in diseased lung (emphysema)
List the 6 layers that gas must diffuse through in alveoli.
- Surfactant
- Alveolar epithelium
- Interstitium
- Pulmonary cap endothelium
- Plasma
- RBC membrane
In lung fibrosis, (diffusion/ventilation) is impaired because there’s a buildup of (X) in (Y) layer.
Diffusion;
X = collagen
Y = interstitial
Distance from surface of alveolus to capillary is about (X).
X = 0.05 mm
Comparing O2 and CO2 diffusion: if area, thickness, and partial pressure gradients are equal, which factors determine diffusion?
- Diffusion constant (dependent on MW)
2. Solubility
(CO2/O2) is (X) times more soluble in water than (CO2/O2).
CO2;
X = 24;
O2
PvCO2 and PvO2 values in pulmonary artery (venous blood).
PvCO2: 46 Torr
PvO2: 40 Torr
PaCO2 and PaO2 values in pulmonary vein (arterial blood).
PaCO2: 40 Torr
PaO2: 100 Torr
T/F: Arterial gas pressures of CO2 and O2 are equal to those in the lung.
True
Pressure gradient in lung for O2 and CO2.
O2: 60 Torr
CO2: 6 Torr
T/F: Due to 10x higher pressure gradient in lung, O2 diffuses about 2x faster than CO2.
False - CO2 diffuses 2x faster due to greater solubility
Gas exchange that is perfusion-limited is dependent on (X). This is the case of (normal/diseased) lung.
X = blood flow (i.e. increased blood flow, increased gas transport);
Normal
Gas exchange that is diffusion-limited is dependent on (X). This is the case of (normal/diseased) lung.
X = diffusion..
Diseased
T/F: PO2 in blood depends on concentration of gas in solution and bound to Hb.
False - partial pressure only depends on concentration of gas in solution
At low concentration of inhaled CO, capillary PCO is about (X) Torr. Why? Is CO diffusion or perfusion limited?
X = 0;
Diffusion limited; binds Hb at very high affinitiy, so diffuses along capillary without equilibrating (negligible amount of CO in solution)
Since He (does/doesn’t) diffuse into blood from alveolar gas, it’s used along with CO to indicate (X).
Doesn’t;
How much original gas mixture was diluted within alveoli
T/F: In diseased lung, non-uniformity can prevent diffusion problem from being detected.
True
Diseased lung: pulmonary edema may be not be detected (aka no change in total lung diffusing capacity). Expliain.
Recruitment of capillaries in other, healthy parts of lung; blood flow bypasses alveoli that may be filled with fluid, so these non-aerated regions won’t contribute to diffusing capacity measurement
Diffusion capacity of lung changes by changing (X) via which mechanisms?
X = Perfusion;
Recruitment and distension
There’s an initial (rise/fall) in alveolar O2 and (rise/fall) in alveolar CO2 during inspiration. What accounts for this?
Fall; rise
Mixing of alveolar gas with gas from dead space
Alveolar PO2 reaches peak rise in (inspiration/expiration) and begin subsequent drop in (inspiration/expiration). This allows comparison of which rates?
Inspiration; inspiration (just before expiration)
Rate of O2 delivery in inspired gas is slower than rate of removal of O2 from alveoli
Alveolar PCO2 reaches peak drop in (inspiration/expiration) and begin subsequent rise in (inspiration/expiration). This allows comparison of which rates?
Inspiration; inspiration (just before expiration)
Rate of CO2 to inspired gas is slower than rate of removal of CO2 from alveoli
In steady state respiration, neither (X) nor (Y) of CO2 and O2 change appreciably over time.
X = flow of gas Y = mean alveolar partial pressures
Fraction of CO2 in alveolar gas is directly proportional to (X) and inversely proportional to (Y).
X = amount CO2 produced each minute (at BTPS) Y = minute alveolar ventilation
The alveolar gas equation allows simple calculation of pressure of (X) at a given (Y).
X = alveolar CO2 Y = CO2 production
RER or RQ is defined as (X) and usually equal to which value(s)?
X = (amount CO2 added into alveoli)/(amount O2 removed from alveoli)
Less than 1 (about 0.8)
Under which condition would RER equal 1?
Pure carbohydrate being metabolized
CO2 stores are (lesser/equal/greater) than/to O2 stores in body. This means alveolar PCO2 take(s) (longer/equal/shorter) time than PO2 to equilibrate.
Greater;
longer
T/F: Oxygen is poorly soluble in plasma.
True
T/F: RBCs are nearly all Hb by volume.
True
RBCs occupy (X)% of blood volume.
X = 40-50
T/F: Myoglobin has heme prosthetic group and binds O2 with higher affinity than Hb.
True
T/F: Hb, but not myoglobin, binds oxygen reversibly.
False - both do
Hb and Mgb: (X) is responsible for preventing irreversible (oxidation/reduction) of (ferrous/ferric) ion to (ferrous/ferric) ion.
X = distal histidine residue
Oxidation;
Ferrous; ferric
Oxygen binding curve for myoglobin has (X) shape. Myoglobin is 50% saturated at (Y) P of O2.
X = hyperbolic X = 2 mmHg (2 Torr)
How many O2 binding sites does myoglobin have?
One
Carbaminohemoglobin has (X) bound. And carboxyhemoglobin has (Y) bound.
X = CO2 Y = CO
T, aka (X), conformation of Hb: O2 (is/isn’t) bound. And Hb has (low/high/equal) affinity for O2 compared to R conformation.
X = taut;
isn’t
Lower
R, aka (X), conformation of Hb: O2 (is/isn’t) bound. And Hb has (low/high/equal) affinity for O2 compared to T conformation.
X = relaxed;
Is;
High
(T/R) conformation of Hb results from rupture of some ionic/H bonds aka salt bridges.
R
Describe the “lever” effect in Hb.
Binding of O2 causes small shift of Fe into plane of heme group, which then causes much larger shift (rotation) in surrounding structure
Binding of first O2 molecule to Hb enhances binding of second by factor of (X). By the time 3 O2 molecules are bound, remaining binding site has (Y) times the affinity for O2.
X = 3; Y = 20
When 50% of Hb oxygenated, most tetramers are bound to either (1/2/3/4) O2 or (1/2/3/4) O2 molecules.
0 (deoxygenated) or 4 (fully oxygenated)
Highest point of Hb saturation is (X)% in lungs. And lowest is (Y)% in tissues. Thus, (Z)% of bound O2 will actually be released in tissues.
X = 98 Y = 32 Z = 66
2,3-DPG stabilizes (oxy/deoxy) form of Hb, thus shifting the O2 binding curve (right/left).
Deoxy;
Right
2,3-DPG is highly (cationic/anionic). It binds (X) part of (oxy/deoxy) Hb.
Anionic;
X = central cavity;
Deoxy-Hb
T/F: Oxygenation of Hb expels 2,3-DPG.
True
Rapidly metabolizing tissue releases high concentrations of (X), which promotes stabilization of (T/R) Hb and (binding/releasing) of O2.
X = H and CO2
T;
Release
T/F: Both Hb and myoglobin display Bohr effect by shifting curves to the right.
False - Mgb shows little Bohr effect
List the two ways that CO2 release from tissues (increases/decreases) O2 affinity of Hb.
Decreases;
- CO2 becomes bicarbonate and protons release (equation shift)
- CO2 reacts with N-term of Hb to form carbamates
Carbamate is formed when (X). This aids in transport of (Y) to (Z).
X = CO2 binds N-term of Hb Y = CO2 Z = lungs
Carbamate formation stabilizes (oxy/deoxy)-Hb state because of the (positive/negative) charged group that stabilizes (X) formation.
Deoxy;
Negative;
X = salt bridge
The Haldane effect describes which phenomenon?
Deoxygenation of blood increases its ability to carry CO2
(X) is the principal Hb in adults. It has how many beta and alpha and gamma chains?
X = Hb alpha
2 beta and 2 alpha
(X) is the principal Hb in fetuses. It has how many beta and alpha and gamma chains?
X = Hb gamma
2 alpha and 2 gamma
(Fetal/maternal) RBC/Hb has higher O2 affinity. This is because (X) instead of (Y) residue causes:
Fetal;
X = serine
Y = histidine
Lowers fetal Hb affinity for DPG
The major site of resistance to airflow within the respiratory system is located in the:
Medium bronchioles
