02a: Ventilation and Diffusion

Question 1

Diffusion becomes the dominant mechanism of gas transport (before/beyond) which point in respiratory tree?

Answer 1

Beyond terminal bronchioles

Question 2

Bulk flow: gas movement results from differences in (X). How does this differ from diffusion?

Answer 2

X = total pressure (i.e. total pressure gradient)

Diffusion: certain gas moves down its own partial pressure gradient

Question 3

Linear velocity of flow is (high/low) in upper airways and (increases/decreases) as it approaches alveolar ducts due to increase in (X).

Answer 3

High;
decreases;
X = cross-sectional area (by nearly 5,000 fold)

Question 4

T/F: Bulk flow essentially ceases in respiratory zone.

Answer 4

False - volume change seen in alveoli

Question 5

Deposition of particulates in alveoli occurs as result of (X). How does the body take care of this?

Answer 5

X = low gas velocity

Macrophages remove the particulates

Question 6

T/F: Diffusion in any lung is not rate-limiting.

Answer 6

False - in normal lung, but diffusion may be limited in diseased lung (emphysema)

Question 7

List the 6 layers that gas must diffuse through in alveoli.

Answer 7

1. Surfactant
2. Alveolar epithelium
3. Interstitium
4. Pulmonary cap endothelium
5. Plasma
6. RBC membrane

Question 8

In lung fibrosis, (diffusion/ventilation) is impaired because there’s a buildup of (X) in (Y) layer.

Answer 8

Diffusion;
X = collagen
Y = interstitial

Question 9

Distance from surface of alveolus to capillary is about (X).

Answer 9

X = 0.05 mm

Question 10

Comparing O2 and CO2 diffusion: if area, thickness, and partial pressure gradients are equal, which factors determine diffusion?

Answer 10

1. Diffusion constant (dependent on MW)

2. Solubility

Question 11

(CO2/O2) is (X) times more soluble in water than (CO2/O2).

Answer 11

CO2;
X = 24;
O2

Question 12

PvCO2 and PvO2 values in pulmonary artery (venous blood).

Answer 12

PvCO2: 46 Torr
PvO2: 40 Torr

Question 13

PaCO2 and PaO2 values in pulmonary vein (arterial blood).

Answer 13

PaCO2: 40 Torr
PaO2: 100 Torr

Question 14

T/F: Arterial gas pressures of CO2 and O2 are equal to those in the lung.

Answer 14

True

Question 15

Pressure gradient in lung for O2 and CO2.

Answer 15

O2: 60 Torr
CO2: 6 Torr

Question 16

T/F: Due to 10x higher pressure gradient in lung, O2 diffuses about 2x faster than CO2.

Answer 16

False - CO2 diffuses 2x faster due to greater solubility

Question 17

Gas exchange that is perfusion-limited is dependent on (X). This is the case of (normal/diseased) lung.

Answer 17

X = blood flow (i.e. increased blood flow, increased gas transport);

Normal

Question 18

Gas exchange that is diffusion-limited is dependent on (X). This is the case of (normal/diseased) lung.

Answer 18

X = diffusion..

Diseased

Question 19

T/F: PO2 in blood depends on concentration of gas in solution and bound to Hb.

Answer 19

False - partial pressure only depends on concentration of gas in solution

Question 20

At low concentration of inhaled CO, capillary PCO is about (X) Torr. Why? Is CO diffusion or perfusion limited?

Answer 20

X = 0;
Diffusion limited; binds Hb at very high affinitiy, so diffuses along capillary without equilibrating (negligible amount of CO in solution)

Question 21

Since He (does/doesn’t) diffuse into blood from alveolar gas, it’s used along with CO to indicate (X).

Answer 21

Doesn’t;

How much original gas mixture was diluted within alveoli

Question 22

T/F: In diseased lung, non-uniformity can prevent diffusion problem from being detected.

Answer 22

True

Question 23

Diseased lung: pulmonary edema may be not be detected (aka no change in total lung diffusing capacity). Expliain.

Answer 23

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

Question 24

Diffusion capacity of lung changes by changing (X) via which mechanisms?

Answer 24

X = Perfusion;

Recruitment and distension

Question 25

There's an initial (rise/fall) in alveolar O2 and (rise/fall) in alveolar CO2 during inspiration. What accounts for this?

Answer 25

Fall; rise Mixing of alveolar gas with gas from dead space

Question 26

Alveolar PO2 reaches peak rise in (inspiration/expiration) and begin subsequent drop in (inspiration/expiration). This allows comparison of which rates?

Answer 26

Inspiration; inspiration (just before expiration) Rate of O2 delivery in inspired gas is slower than rate of removal of O2 from alveoli

Question 27

Alveolar PCO2 reaches peak drop in (inspiration/expiration) and begin subsequent rise in (inspiration/expiration). This allows comparison of which rates?

Answer 27

Inspiration; inspiration (just before expiration) Rate of CO2 to inspired gas is slower than rate of removal of CO2 from alveoli

Question 28

In steady state respiration, neither (X) nor (Y) of CO2 and O2 change appreciably over time.

Answer 28

``` X = flow of gas Y = mean alveolar partial pressures ```

Question 29

Fraction of CO2 in alveolar gas is directly proportional to (X) and inversely proportional to (Y).

Answer 29

``` X = amount CO2 produced each minute (at BTPS) Y = minute alveolar ventilation ```

Question 30

The alveolar gas equation allows simple calculation of pressure of (X) at a given (Y).

Answer 30

``` X = alveolar CO2 Y = CO2 production ```

Question 31

RER or RQ is defined as (X) and usually equal to which value(s)?

Answer 31

X = (amount CO2 added into alveoli)/(amount O2 removed from alveoli) Less than 1 (about 0.8)

Question 32

Under which condition would RER equal 1?

Answer 32

Pure carbohydrate being metabolized

Question 33

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.

Answer 33

Greater; | longer

Question 34

T/F: Oxygen is poorly soluble in plasma.

Answer 34

True

Question 35

T/F: RBCs are nearly all Hb by volume.

Answer 35

True

Question 36

RBCs occupy (X)% of blood volume.

Answer 36

X = 40-50

Question 37

T/F: Myoglobin has heme prosthetic group and binds O2 with higher affinity than Hb.

Answer 37

True

Question 38

T/F: Hb, but not myoglobin, binds oxygen reversibly.

Answer 38

False - both do

Question 39

Hb and Mgb: (X) is responsible for preventing irreversible (oxidation/reduction) of (ferrous/ferric) ion to (ferrous/ferric) ion.

Answer 39

X = distal histidine residue Oxidation; Ferrous; ferric

Question 40

Oxygen binding curve for myoglobin has (X) shape. Myoglobin is 50% saturated at (Y) P of O2.

Answer 40

``` X = hyperbolic X = 2 mmHg (2 Torr) ```

Question 41

How many O2 binding sites does myoglobin have?

Answer 41

One

Question 42

Carbaminohemoglobin has (X) bound. And carboxyhemoglobin has (Y) bound.

Answer 42

``` X = CO2 Y = CO ```

Question 43

T, aka (X), conformation of Hb: O2 (is/isn't) bound. And Hb has (low/high/equal) affinity for O2 compared to R conformation.

Answer 43

X = taut; isn't Lower

Question 44

R, aka (X), conformation of Hb: O2 (is/isn't) bound. And Hb has (low/high/equal) affinity for O2 compared to T conformation.

Answer 44

X = relaxed; Is; High

Question 45

(T/R) conformation of Hb results from rupture of some ionic/H bonds aka salt bridges.

Answer 45

R

Question 46

Describe the "lever" effect in Hb.

Answer 46

Binding of O2 causes small shift of Fe into plane of heme group, which then causes much larger shift (rotation) in surrounding structure

Question 47

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.

Answer 47

``` X = 3; Y = 20 ```

Question 48

When 50% of Hb oxygenated, most tetramers are bound to either (1/2/3/4) O2 or (1/2/3/4) O2 molecules.

Answer 48

0 (deoxygenated) or 4 (fully oxygenated)

Question 49

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.

Answer 49

``` X = 98 Y = 32 Z = 66 ```

Question 50

2,3-DPG stabilizes (oxy/deoxy) form of Hb, thus shifting the O2 binding curve (right/left).

Answer 50

Deoxy; | Right

Question 51

2,3-DPG is highly (cationic/anionic). It binds (X) part of (oxy/deoxy) Hb.

Answer 51

Anionic; X = central cavity; Deoxy-Hb

Question 52

T/F: Oxygenation of Hb expels 2,3-DPG.

Answer 52

True

Question 53

Rapidly metabolizing tissue releases high concentrations of (X), which promotes stabilization of (T/R) Hb and (binding/releasing) of O2.

Answer 53

X = H and CO2 T; Release

Question 54

T/F: Both Hb and myoglobin display Bohr effect by shifting curves to the right.

Answer 54

False - Mgb shows little Bohr effect

Question 55

List the two ways that CO2 release from tissues (increases/decreases) O2 affinity of Hb.

Answer 55

Decreases; 1. CO2 becomes bicarbonate and protons release (equation shift) 2. CO2 reacts with N-term of Hb to form carbamates

Question 56

Carbamate is formed when (X). This aids in transport of (Y) to (Z).

Answer 56

``` X = CO2 binds N-term of Hb Y = CO2 Z = lungs ```

Question 57

Carbamate formation stabilizes (oxy/deoxy)-Hb state because of the (positive/negative) charged group that stabilizes (X) formation.

Answer 57

Deoxy; Negative; X = salt bridge

Question 58

The Haldane effect describes which phenomenon?

Answer 58

Deoxygenation of blood increases its ability to carry CO2

Question 59

(X) is the principal Hb in adults. It has how many beta and alpha and gamma chains?

Answer 59

X = Hb alpha 2 beta and 2 alpha

Question 60

(X) is the principal Hb in fetuses. It has how many beta and alpha and gamma chains?

Answer 60

X = Hb gamma 2 alpha and 2 gamma

Question 61

(Fetal/maternal) RBC/Hb has higher O2 affinity. This is because (X) instead of (Y) residue causes:

Answer 61

Fetal; X = serine Y = histidine Lowers fetal Hb affinity for DPG

Question 62

The major site of resistance to airflow within the respiratory system is located in the:

Answer 62

Medium bronchioles