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Gas Transport

Total questions: 175

Worksheet time: 1hrs 28mins

Name
Class
Date
1.

Gases in the alveoli come into equilibrium with blood mainly by:

a)

Active transport across cartilage

b)

Diffusion across pulmonary epithelium and capillary walls

c)

Osmosis across bronchioles

d)

Filtration through pleura

2.

The driving force for diffusion of gases between alveoli and blood is:

a)

Temperature difference only

b)

Differences in partial pressure

c)

Gravity

d)

Blood viscosity

3.

Partial pressure is:

a)

Pressure of water vapour only

b)

Pressure exerted by an individual gas in a mixture

c)

Total pressure of a gas mixture

d)

Pressure inside alveoli only

4.

Dalton's law of partial pressures states that total pressure equals:

a)

The highest gas pressure in the mixture

b)

The average of all gas pressures

c)

The sum of individual gas partial pressures

d)

The pressure of oxygen only

5.

In a gas mixture, each gas exerts:

a)

No pressure independently

b)

A partial pressure independent of other gases

c)

Pressure only if reactive

d)

Pressure only in blood

6.

At sea level, barometric pressure typically supports a mercury column of:

a)

76 mm

b)

760 mm

c)

160 mm

d)

104 mm

7.

If oxygen is ~21% of atmospheric air at sea level, its partial pressure is approximately:

a)

21 mmHg

b)

104 mmHg

c)

160 mmHg

d)

760 mmHg

8.

Atmospheric CO2 is ~0.04% of air; its partial pressure at sea level is approximately:

a)

40 mmHg

b)

0.3 mmHg

c)

3 mmHg

d)

30 mmHg

9.

The PO2 gradient from dry inspired air to alveolar air is from:

a)

104 -> 160 mmHg

b)

160 -> 104 mmHg

c)

100 -> 40 mmHg

d)

40 -> 100 mmHg

10.

The PO2 drop from 160 to 104 mmHg is due to:

a)

Increased nitrogen partial pressure

b)

Increased water vapour partial pressure

c)

Increased haemoglobin concentration

d)

Increased temperature only

11.

In the slide equation, total pressure for dry air is shown as:

a)

Pdry = PN2 + PO2 + PCO2 = 760 mmHg

b)

Pdry = PO2 + PH2O = 760 mmHg

c)

Pdry = PN2 + PO2 = 104 mmHg

d)

Pdry = PO2 + PCO2 + PH2O = 760 mmHg

12.

In the slide equation, total pressure for wet air is:

a)

Pwet = PN2 + PO2 + PCO2 + PH2O = 760 mmHg

b)

Pwet = PN2 + PO2 + PCO2 = 160 mmHg

c)

Pwet = PO2 + PH2O = 104 mmHg

d)

Pwet = PN2 + PH2O = 760 mmHg

13.

Typical alveolar PO2 shown is:

a)

160 mmHg

b)

104 mmHg

c)

100 mmHg

d)

40 mmHg

14.

Typical alveolar PCO2 shown is:

a)

45 mmHg

b)

46 mmHg

c)

40 mmHg

d)

0.3 mmHg

15.

Typical pulmonary blood (entering alveolar capillary) PO2 shown is:

a)

40 mmHg

b)

104 mmHg

c)

100 mmHg

d)

160 mmHg

16.

Typical pulmonary blood (entering alveolar capillary) PCO2 shown is:

a)

40 mmHg

b)

45 mmHg

c)

0.3 mmHg

d)

46 mmHg

17.

Fick's law (slide) says diffusion across an alveolar membrane depends on:

a)

Heart rate and blood pressure

b)

Partial pressure difference and surface area

c)

Lung volume only

d)

Bronchial cartilage thickness only

18.

According to the slide, gas diffuses faster when:

a)

Surface area decreases

b)

Pressure difference increases

c)

Temperature decreases only

d)

Thickness increases

19.

In the slide formula, the "A" represents:

a)

Atmospheric pressure

b)

Area for gas exchange

c)

Amount of oxygen in blood

d)

Affinity of haemoglobin

20.

In the slide formula, the "D" represents:

a)

Distance (thickness) of barrier to diffusion

b)

Dalton's constant

c)

Density of blood

d)

Depth of breathing

21.

In the slide formula, (P2 - P1) represents:

a)

Temperature gradient

b)

Difference in partial pressure on each side

c)

Total alveolar pressure

d)

Haemoglobin saturation

22.

The diffusion constant "k" depends on:

a)

Solubility of gas and temperature

b)

Pleural pressure only

c)

Rib cage movement

d)

Oxygen content only

23.

"Gas transport" (overall) includes exchange between lungs and blood and:

a)

Only filtration by kidneys

b)

Transport of gases in blood to tissues

c)

Muscle contraction only

d)

Nerve impulses only

24.

Oxygen is transported in blood in two forms:

a)

Dissolved in plasma and dissolved in RBCs only

b)

Dissolved in plasma and chemically bound to haemoglobin

c)

Bound to albumin and to platelets

d)

As bicarbonate only

25.

More than 98% of oxygen in blood is:

a)

Dissolved in plasma

b)

Bound to haemoglobin

c)

Bound to CO2

d)

Bound to water vapour

26.

PO2 in arterial blood (slide) is approximately:

a)

40 mmHg

b)

100 mmHg

c)

104 mmHg

d)

160 mmHg

27.

PO2 in tissues (slide) is approximately:

a)

160 mmHg

b)

104 mmHg

28.

In a person at rest, intracellular PO2 averages about:

a)

100 mmHg

b)

40 mmHg

c)

104 mmHg

d)

160 mmHg

29.

Oxygen diffuses from blood to tissues because:

a)

PO2 is higher in cells than blood

b)

PO2 is lower in cells than arterial blood

c)

PCO2 is lower in cells than blood

d)

Total pressure is higher in cells

30.

Returning venous blood will have PO2 approximately equal to:

a)

Alveolar PO2

b)

Arterial PO2 always

c)

The cells it just passed

d)

Atmospheric PO2

31.

Oxygen has poor solubility in blood of approximately:

a)

2.5 mL/100 mL blood

b)

0.25 mL/100 mL blood

c)

20 mL/100 mL blood

d)

1.5 mL/100 mL blood

32.

Blood contains about ___ mL O2 per 100 mL blood (total):

a)

0.25

b)

2.0

c)

20

d)

200

33.

Approximately what percent of total blood O2 is dissolved (slide)?

a)

98.5%

b)

50%

c)

1.5%

d)

21%

34.

Approximately what percent of total blood O2 is bound to haemoglobin (slide)?

a)

1.5%

b)

98.5%

c)

40%

d)

0.04%

35.

Haemoglobin greatly increases blood's capacity to transport oxygen because it binds oxygen:

a)

Irreversibly

b)

Reversibly

c)

Only in tissues

d)

Only in plasma

36.

Typical haemoglobin concentration in men (slide range) is:

a)

40-60 g/L

b)

140-180 g/L

c)

120-160 g/L

d)

200-240 g/L

37.

Typical haemoglobin concentration in women (slide range) is:

a)

140-180 g/L

b)

10-20 g/L

c)

120-160 g/L

d)

180-220 g/L

38.

Haemoglobin molecule is composed of:

a)

Two peptide chains total

b)

Four peptide chains total (2 alpha and 2 beta)

c)

One peptide chain and one lipid

d)

Four DNA strands

39.

Each peptide chain is attached to a:

a)

Sodium ion

b)

Heme ring

c)

Cartilage ring

d)

Bicarbonate group

40.

The metal atom bound in the centre of each heme ring is:

a)

Calcium

b)

Iron

c)

Sodium

d)

Magnesium

41.

An oxygen molecule attaches to:

a)

The peptide chain directly

b)

The iron atom in heme

c)

The plasma proteins

d)

The RBC membrane

42.

Each haemoglobin molecule can bind up to:

a)

1 oxygen molecule

b)

2 oxygen molecules

c)

3 oxygen molecules

d)

4 oxygen molecules

43.

Hb bound with oxygen is called:

a)

Deoxyhaemoglobin

b)

Oxyhaemoglobin

c)

Carbaminohaemoglobin

d)

Methemoglobin (not in slide)

44.

Hb not bound with oxygen is called:

a)

Oxyhaemoglobin

b)

Deoxyhaemoglobin

c)

Oxycarbonic acid

d)

Bicarbonate

45.

The oxygen-haemoglobin dissociation curve relates PO2 to:

a)

Blood glucose

b)

Percent haemoglobin saturation

c)

Pleural pressure

d)

Total lung volume

46.

As oxygen concentration increases, the slide states there is:

a)

Decrease in Hb binding

b)

Progressive increase in binding to Hb

c)

No change in Hb binding

d)

Progressive decrease in saturation

47.

Hb binding is highest in:

a)

Tissue capillaries

b)

Pulmonary capillaries

c)

Venous blood in exercise only

d)

Intracellular fluid

48.

The relationship is not linear but:

a)

Straight line

b)

Sigmoid

c)

Exponential only

d)

Random

49.

The curve is sigmoid due to:

a)

Water vapour pressure

b)

Cooperative binding of oxygen to haemoglobin

c)

Viscosity changes

d)

RBC shape only

50.

Oxygen-carrying capacity is defined as:

a)

Actual amount of O2 bound to Hb

b)

Maximum amount of O2 Hb can transport

c)

Ratio of O2 content to barometric pressure

d)

Amount of dissolved O2 only

51.

Oxygen content is defined as:

a)

Maximum O2 Hb can transport

b)

Actual amount of O2 bound to Hb

c)

Amount of CO2 in blood

d)

Total pressure of oxygen in alveoli

52.

Oxygen saturation is defined as:

a)

Oxygen content / oxygen-carrying capacity

b)

Oxygen-carrying capacity / oxygen content

c)

PO2 / PCO2

d)

Total pressure / partial pressure

53.

Main factors shifting the dissociation curve include:

a)

pH, CO2 concentration, temperature

b)

Na+, K+, Cl-

c)

Water vapour, nitrogen, helium

d)

Blood pressure, heart rate, lung volume

54.

A right shift indicates:

a)

Increased O2 affinity of Hb

b)

Decreased O2 affinity of Hb

c)

No change in affinity

d)

Hb cannot release O2

55.

With a right shift, it is ___ for Hb to bind oxygen:

a)

Easier

b)

More difficult

56.

With a right shift, to achieve the same oxygen saturation Hb requires:

a)

Lower PO2

b)

Higher PO2

c)

Same PO2 always

d)

Lower PCO2

57.

A right shift makes it ___ for Hb to release oxygen:

a)

Harder

b)

Easier

c)

Unchanged

d)

Impossible

58.

A left shift indicates:

a)

Decreased O2 affinity

b)

Increased O2 affinity

c)

No change

d)

Loss of cooperative binding

59.

With a left shift, Hb binds oxygen:

a)

More easily

b)

Less easily

c)

Only in tissues

d)

Only in alveoli

60.

With a left shift, Hb unloads oxygen:

a)

More readily

b)

More reluctantly

c)

Not at all

d)

Only during exercise

61.

In the alveolus diagram, alveolar PO2 is higher than pulmonary blood PO2, so oxygen diffuses:

a)

Blood -> alveolus

b)

Alveolus -> blood

c)

Tissue -> blood

d)

Blood -> tissue

62.

In the same diagram, pulmonary blood PCO2 is higher than alveolar PCO2, so CO2 diffuses:

a)

Blood -> alveolus

b)

Alveolus -> blood

c)

Tissue -> blood

d)

Blood -> tissue

63.

In tissue (slide), oxygen is more concentrated in:

a)

Cells than blood

b)

Blood than cells

c)

Alveoli than blood

d)

Plasma than RBCs always

64.

In tissue (slide), carbon dioxide is more concentrated in:

a)

Blood than cells

b)

Cells than blood

c)

Alveoli than blood

d)

Atmospheric air than cells

65.

The "gradient is reversed" when arterial blood reaches tissue capillaries refers to:

a)

O2 now moving into blood

b)

Direction of diffusion changing between lungs vs tissues

c)

Total pressure becoming 760 mmHg

d)

Water vapour disappearing

66.

Which value pair matches alveolar air shown?

a)

PO2 40, PCO2 45

b)

PO2 104, PCO2 40

c)

PO2 160, PCO2 0.3

d)

PO2 100, PCO2 46

67.

Which value pair matches pulmonary blood shown?

a)

PO2 104, PCO2 40

b)

PO2 100, PCO2 40

c)

PO2 40, PCO2 45

d)

PO2 160, PCO2 0.3

68.

The slide indicates PO2 in arterial blood is:

a)

Equal to tissue PO2

b)

Higher than tissue PO2

c)

Lower than tissue PO2

d)

Always 160 mmHg

69.

The slide indicates tissue PO2 is:

a)

Higher than arterial PO2

b)

Lower than arterial PO2

c)

Equal to alveolar PO2

d)

Equal to atmospheric PO2

70.

Dissolved oxygen in plasma is best described as:

a)

The major portion of blood O2

b)

A small portion compared with Hb-bound O2

c)

The only form of oxygen transport

d)

Greater than 50% of total O2

71.

"This is insufficient for mammalian respiration" refers to:

a)

Hb-bound oxygen

b)

Dissolved oxygen alone

c)

CO2 transport

d)

Water vapour pressure

72.

The slide shows oxygen transport from lungs to cells involves:

a)

Only dissolved oxygen diffusion

b)

Hb binding in RBCs and unloading at tissues

c)

Only CO2 diffusion

d)

Only water vapour exchange

73.

Hb has how many heme groups?

a)

1

b)

2

c)

3

d)

4

74.

Each heme group can bind:

a)

Up to 2 O2

b)

1 O2

c)

4 O2

d)

0 O2

75.

The dissociation curve is useful because it links PO2 to:

a)

Hb structure (alpha/beta chains) only

b)

Hb saturation (%)

c)

Total barometric pressure only

d)

Alveolar surface area only

76.

"Cooperative binding" means:

a)

Hb binds O2 at random

b)

Binding of O2 influences further binding (sigmoid curve)

c)

O2 binds only to plasma proteins

d)

O2 binds only in tissues

77.

The curve's "sigmoid" shape indicates:

a)

No change in saturation with PO2

b)

Non-linear relationship between PO2 and saturation

c)

CO2 cannot diffuse

d)

O2 transport is only dissolved

78.

Which is a correct definition pair?

a)

Oxygen content = maximum O2 Hb can carry

b)

Oxygen saturation = oxygen content / oxygen-carrying capacity

c)

Oxygen-carrying capacity = actual O2 bound

d)

Oxygen saturation = PO2 / PCO2

79.

Increasing CO2 concentration (factor listed) is associated with:

a)

A shift on the dissociation curve (per slide)

b)

No effect on Hb at all

c)

Increased barometric pressure only

d)

Increased water vapour only

80.

Decreasing pH (factor listed) is associated with:

a)

A shift on the dissociation curve (per slide)

b)

No effect on oxygen binding

c)

Increased alveolar PO2 to 160 always

d)

Decreased total pressure to 104

81.

Increasing temperature (factor listed) is associated with:

a)

A shift on the dissociation curve (per slide)

b)

No effect on Hb

c)

Only affects Dalton's law

d)

Only affects barometric pressure

82.

A right shift generally supports:

a)

Easier loading of O2 in lungs and harder release in tissues

b)

Harder loading in lungs and easier release in tissues

c)

No O2 release

d)

Permanent O2 binding

83.

A left shift generally supports:

a)

Easier loading of O2 in lungs and harder release in tissues

b)

Harder loading in lungs and easier release in tissues

c)

No change in O2 affinity

d)

Permanent O2 binding

84.

In Fick's law, if membrane area increases, diffusion rate:

a)

Decreases

b)

Increases

c)

Stays the same

d)

Becomes zero

85.

In Fick's law, if thickness (distance) increases, diffusion rate:

a)

Increases

b)

Decreases

c)

Unchanged

d)

Becomes independent of pressure

86.

In Fick's law, if partial pressure difference increases, diffusion rate:

a)

Decreases

b)

Increases

c)

Becomes zero

d)

Depends only on water vapour

87.

The slide describes diffusion as occurring across:

a)

Pulmonary epithelium and capillary walls

b)

Pleural membranes only

c)

Tracheal cartilage only

d)

Diaphragm only

88.

"Equilibrium with the blood" means:

a)

No gas exchange occurs

b)

Gases reach balance via diffusion

c)

Only oxygen moves, CO2 does not

d)

Only CO2 moves, O2 does not

89.

Which statement matches Dalton's law concept?

a)

Total pressure is unrelated to partial pressures

b)

Total pressure is the sum of partial pressures

c)

Partial pressure cannot be calculated

d)

Only oxygen contributes to total pressure

90.

If barometric pressure is 760760 mmHg and O2 is 21%21\% , PO2 is:

a)

0.210.21 mmHg

b)

2121 mmHg

c)

160160 mmHg

d)

104104 mmHg

91.

If CO2 is 0.04%0.04\% of atmospheric air, its partial pressure is closest to:

a)

44 mmHg

b)

0.30.3 mmHg

c)

3030 mmHg

d)

4040 mmHg

92.

The slide's alveolar PO2 ( 104104 ) is lower than atmospheric PO2 ( 160160 ) mainly due to:

a)

Increased PCO2

b)

Water vapour pressure contribution

c)

Increased haemoglobin

d)

Increased diffusion constant k

93.

At rest, cells have PO2 about:

a)

160160 mmHg

b)

104104 mmHg

c)

100100 mmHg

d)

4040 mmHg

94.

At rest, arterial blood arriving at cells has PO2 about:

a)

4040 mmHg

b)

100100 mmHg

c)

104104 mmHg

d)

0.30.3 mmHg

95.

The slide indicates venous blood leaving tissues has PO2 about:

a)

Same as arterial blood ( 100100 )

b)

Same as alveoli ( 104104 )

c)

Same as cells (~ 4040 )

d)

Same as atmosphere ( 160160 )

96.

The majority of oxygen transport in blood is due to:

a)

Solubility in plasma

b)

Binding to haemoglobin in RBCs

c)

Binding to CO2 in plasma

d)

Binding to water vapour

97.

The dissociation curve "shift" concept refers to:

a)

Changing barometric pressure only

b)

Changing Hb affinity for oxygen

c)

Changing total blood volume

d)

Changing number of alveoli

98.

A right shift indicates:

a)

Increased affinity and reluctant unloading

b)

Decreased affinity and easier unloading

c)

No cooperative binding

d)

Oxygen can't diffuse

99.

A left shift indicates:

a)

Decreased affinity and easier unloading

b)

Increased affinity and reluctant unloading

c)

No Hb binding in lungs

d)

Complete loss of oxygen content

100.

In the slide's dissociation curve notes, the relationship is highest in pulmonary capillaries because:

a)

PO2 is lowest there

b)

O2 concentration is high and Hb binding increases

c)

CO2 concentration is highest there

d)

Water vapour is absent there

101.

Which of the following best describes gas movement between alveoli and blood?

a)

Diffusion down partial pressure gradients across the alveolar-capillary barrier.

b)

Bulk flow from alveoli to blood driven by pressure differences.

c)

Active transport by alveolar cells.

d)

Facilitated diffusion via channels.

e)

Convection through respiratory bronchioles.

102.

Which of the following is TRUE regarding oxygen diffusion into pulmonary capillaries?

a)

It requires active transport across the endothelium.

b)

It occurs until blood PO2 equilibrates with alveolar PO2 across a thin membrane.

c)

It depends solely on hemoglobin concentration.

d)

It is limited only by cardiac output.

e)

It is unaffected by membrane thickness.

103.

Which of the following is most important for maintaining alveolar gas equilibrium?

a)

High 2,3-DPG levels.

b)

High hemoglobin concentration.

c)

Body temperature.

d)

Matching of ventilation and perfusion and diffusion across thin membrane.

e)

Plasma protein concentration.

104.

What does Dalton's law state regarding gas mixtures?

a)

Total pressure equals the sum of partial pressures of each gas.

b)

Partial pressure is independent of gas fraction.

c)

Gas diffusion rate is proportional to membrane thickness.

d)

Oxygen dissolves poorly in plasma.

e)

Total pressure depends only on temperature.

105.

Which of the following best describes 'partial pressure' of a gas?

a)

Pressure that an individual gas would exert if it alone occupied the volume.

b)

Total pressure of a gas mixture.

c)

Pressure due to water vapor only.

d)

Pressure inside hemoglobin.

e)

Atmospheric pressure minus water vapor pressure.

106.

At sea level (760 mmHg), what is the approximate partial pressure of inspired dry oxygen?

a)

104 mmHg

b)

160 mmHg

c)

21 mmHg

d)

760 mmHg

e)

40 mmHg

107.

Which of these values best represents atmospheric (barometric) pressure at sea level used in calculations?

a)

760 mmHg

b)

104 mmHg

c)

100 mmHg

d)

160 mmHg

e)

40 mmHg

108.

What is the approximate percentage of atmospheric CO2 at sea level and its partial pressure?

a)

0.2% and 1.5 mmHg

b)

1% and 7.6 mmHg

c)

4% and 30 mmHg

d)

21% and 160 mmHg

e)

0.04% and ~0.3 mmHg

109.

Which is the best definition of 'barometric pressure' in respiratory physiology?

a)

Ambient atmospheric pressure (≈760 mmHg at sea level) used to calculate partial pressures.

b)

Pressure inside alveoli during inspiration.

c)

Partial pressure of water vapor.

d)

Pressure in pulmonary capillaries.

e)

Transpulmonary pressure.

110.

Which is the main reason CO2 partial pressure in inspired air is negligible?

a)

CO2 is rapidly absorbed by alveoli.

b)

CO2 binds to hemoglobin in air.

c)

CO2 diffuses out of atmosphere constantly.

d)

Because CO2 is lighter than O2.

e)

Atmospheric CO2 fraction is ~0.04%, giving very low partial pressure at sea level (~0.3 mmHg).

111.

Why does alveolar PO2 decrease from 160 mmHg (dry inspired) to ~104 mmHg?

a)

Because atmospheric O2 fraction decreases.

b)

Due to increased CO2 in alveoli.

c)

Water vapor pressure and gas exchange lower PO2 in alveoli.

d)

Barometric pressure rises in alveoli.

e)

Because hemoglobin removes oxygen instantly.

112.

What is the approximate partial pressure of CO2 in alveolar air?

a)

0.3 mmHg

b)

160 mmHg

c)

21 mmHg

d)

40 mmHg

e)

104 mmHg

113.

Which value approximates alveolar PO2 under normal conditions?

a)

160 mmHg

b)

100 mmHg

c)

104 mmHg

d)

40 mmHg

e)

0.3 mmHg

114.

If alveolar PO2 is 104 mmHg and arterial PO2 is 100 mmHg, what causes this gradient?

a)

Hemoglobin binding in alveoli.

b)

Atmospheric pressure change.

c)

Alveolar collapse.

d)

Mixing with venous blood and physiologic shunt causing slight difference.

e)

Measurement error.

115.

Which of these is TRUE about water vapor in inspired air?

a)

It increases the PO2 of inspired air.

b)

It reduces the effective partial pressure of other gases in the alveoli.

c)

It has no effect on alveolar gas composition.

d)

It increases barometric pressure.

e)

It increases alveolar PCO2.

116.

Which statement best describes physiologic shunt contributing to A–a gradient?

a)

It occurs when inspired air has low O2 fraction only.

b)

It is due to high hemoglobin only.

c)

It increases solubility of O2.

d)

Some venous blood bypasses ventilated alveoli, mixing with arterial blood and lowering PaO2.

e)

It is only present in disease.

117.

Which best describes why arterial PO2 is not equal to alveolar PO2?

a)

Because hemoglobin consumes O2 inside alveoli.

b)

Because atmospheric PCO2 fluctuates rapidly.

c)

Due to small physiologic shunt and V/Q mismatch, causing A–a gradient.

d)

Because diffusion is instantaneous.

e)

Because hemoglobin increases PO2 in arterial blood.

118.

Which circumstance would most likely decrease arterial O2 saturation?

a)

Hypothermia.

b)

Alkalosis.

c)

Low CO2.

d)

Hypoventilation leading to increased alveolar CO2 and lower PO2.

e)

Decreased 2,3-DPG.

119.

Which of the following best describes the role of water vapor pressure in the alveoli?

a)

It increases total barometric pressure.

b)

It reduces partial pressures available to other gases in humidified alveolar air.

c)

It increases alveolar PO2 above inspired dry air values.

d)

It only affects CO2, not O2.

e)

It converts O2 to water.

120.

Which of the following reduces the effective inspired PO2 available for gas exchange?

a)

Increased barometric pressure.

b)

Addition of water vapor in the airways.

c)

Increased fraction of inspired oxygen.

d)

High altitude.

e)

Hyperventilation.

121.

Which factor does NOT appear in Fick's law of diffusion?

a)

Surface area (A).

b)

Diffusion constant (D).

c)

Partial pressure difference (ΔP).

d)

Thickness (distance).

e)

Heart rate.

122.

According to Fick's law, increasing membrane thickness will have what effect on diffusion rate?

a)

Increase it.

b)

Decrease it.

c)

No effect.

d)

Double it.

e)

Change diffusion constant.

123.

Which of the following increases the rate of diffusion according to Fick's law?

a)

Increasing surface area (A).

b)

Increasing membrane thickness.

c)

Decreasing partial pressure difference.

d)

Reducing diffusion constant.

e)

Increasing distance.

124.

Which principle explains why gas exchange efficiency is high in lungs?

a)

High capillary blood flow only.

b)

High oxygen solubility.

c)

Large surface area and thin diffusion barrier as per Fick's law.

d)

Active pump across alveoli.

e)

High temperature of alveoli.

125.

What happens to diffusion rate if the diffusion constant (D) increases?

a)

Diffusion rate increases.

b)

Diffusion rate decreases.

c)

No change.

d)

It depends on surface area only.

e)

It becomes zero.

126.

Why is CO2 diffusion often more rapid than O2 despite lower partial pressure gradients?

a)

CO2 has higher atmospheric fraction.

b)

CO2 binds more to hemoglobin.

c)

CO2 is more soluble and has a higher diffusion constant.

d)

CO2 uses active transport.

e)

CO2 is carried only as bicarbonate.

127.

What is the primary determinant of oxygen diffusion rate from alveoli to blood?

a)

Partial pressure difference across the alveolar membrane.

b)

Arterial oxygen content only.

c)

Hemoglobin saturation only.

d)

Pulmonary blood flow only.

e)

Body temperature only.

128.

Which is TRUE about the diffusion distance for gas exchange?

a)

Greater distance increases diffusion rate.

b)

Greater distance decreases diffusion rate.

c)

Distance has no effect.

d)

Distance only matters for CO2.

e)

It is unrelated to alveolar surface area.

129.

Which best explains the importance of surface area in pulmonary diffusion?

a)

More alveolar surface area increases gas exchange capacity per Fick's law.

b)

Surface area only matters for CO2.

c)

Surface area is irrelevant if diffusion constant is high.

d)

Surface area decreases diffusion.

e)

Surface area only affects convection.

130.

What is the effect of reduced alveolar surface area (e.g., in emphysema)?

a)

Increased diffusion rate

b)

Reduced gas exchange and hypoxemia

c)

Higher PO2 in tissues

d)

Increased hemoglobin affinity

e)

Lower atmospheric pressure

131.

Which of the following is most important for oxygen diffusion across the alveolar–capillary membrane during exercise?

a)

Maintaining adequate alveolar PO2 and capillary recruitment to preserve diffusion rate

b)

Decreasing surface area

c)

Increasing membrane thickness

d)

Reducing cardiac output

e)

Lowering hemoglobin level dramatically

132.

Which of the following would you expect in a patient with impaired diffusion across the alveolar membrane?

a)

Normal PaO2

b)

Hypoxemia due to reduced diffusion rate from alveoli to blood

c)

Increased O2 content despite low PO2

d)

Unchanged alveolar–arterial gradient

e)

Elevated atmospheric pressure effect only

133.

Which of the following is least relevant to Fick’s law application in pulmonary gas exchange?

a)

Surface area of alveoli

b)

Membrane thickness

c)

Partial pressure gradient

d)

Plasma sodium concentration

e)

Diffusion constant of the gas

134.

What percentage of oxygen in blood is typically bound to hemoglobin?

a)

<1%

b)

10%

c)

~98%

d)

50%

e)

100%

135.

Carbon dioxide is transported in blood in which forms?

a)

Only dissolved in plasma

b)

Dissolved, chemically as bicarbonate, and bound to proteins (carbamino compounds)

c)

Only bound to hemoglobin

d)

Only as carbonic acid inside red blood cells

e)

Only as carbon monoxide

136.

Which statement about partial pressure and concentration is correct?

a)

Partial pressure equals gas concentration in all cases

b)

Higher concentration always means higher partial pressure regardless of solubility

c)

Partial pressure drives diffusion and is independent of how much is bound to carriers like hemoglobin

d)

Only dissolved gas contributes nothing to partial pressure

e)

Bound oxygen contributes fully to PO2 measurements

137.

Which best characterizes the relationship between dissolved oxygen and PaO2?

a)

PaO2 reflects dissolved O2 and drives diffusion; dissolved amount is proportional to PaO2

b)

PaO2 reflects total O2 including that bound to hemoglobin

c)

Dissolved O2 is independent of PaO2

d)

PaO2 measures only bound O2

e)

Dissolved O2 determines hemoglobin concentration

138.

What is the arterial PO2 under normal conditions?

a)

40 mmHg

b)

100 mmHg

c)

104 mmHg

d)

160 mmHg

e)

760 mmHg

139.

What is the typical venous PO2 returning from tissues?

a)

40 mmHg

b)

100 mmHg

c)

104 mmHg

d)

160 mmHg

e)

80 mmHg

140.

What drives oxygen diffusion from capillaries into tissues?

a)

Active transport by endothelial cells

b)

Convection only

c)

Binding to myoglobin solely

d)

Partial pressure gradient: higher PO2 in blood than tissues

e)

Electrical gradients

141.

Which best explains why tissues with PO2 ~40 mmHg receive oxygen from arterial blood?

a)

Because tissue PO2 is higher than arterial PO2

b)

Because arterial PO2 (~100 mmHg) is higher, driving diffusion into tissues

c)

Because hemoglobin releases oxygen only at alveoli

d)

Because blood flow is low

e)

Because myoglobin extracts oxygen first

142.

How much oxygen (mL) is dissolved in 100 mL blood at normal PaO2 (~100 mmHg)?

a)

98.5 mL

b)

50 mL

c)

4 mL

d)

0.25 mL

e)

25 mL

143.

Which statement best describes hemoglobin’s binding to oxygen?

a)

Hemoglobin irreversibly binds oxygen

b)

Hemoglobin binds oxygen reversibly, increasing oxygen‑carrying capacity

c)

Hemoglobin cannot bind more than one O2 molecule

d)

Hemoglobin only carries carbon dioxide, not oxygen

e)

Hemoglobin dissolves oxygen in plasma

144.

What is the main reason dissolved oxygen alone is insufficient for mammalian respiration?

a)

It diffuses too slowly

b)

Low solubility in blood provides too little oxygen content

c)

It binds too strongly to plasma proteins

d)

It causes high blood pressure

e)

It cannot cross membranes

145.

Which statement about oxygen content vs oxygen saturation is true?

a)

Content and saturation always change together equally

b)

Oxygen content depends on both hemoglobin concentration and saturation, while saturation is percent of hemoglobin binding sites occupied

c)

Saturation measures dissolved oxygen only

d)

Content is independent of hemoglobin

e)

Saturation equals PO2 numerically

146.

Which of the following increases hemoglobin’s oxygen‑carrying capacity the most?

a)

Increased plasma dissolved oxygen

b)

Presence of functional hemoglobin

c)

Decreased hemoglobin concentration

d)

Lower pH

e)

Higher temperature

147.

Why does hemoglobin greatly increase the oxygen carrying capacity of blood?

a)

It increases PO2

b)

It dissolves oxygen in plasma

c)

It binds oxygen reversibly, allowing large amounts to be transported without increasing PO2

d)

It converts oxygen to carbon dioxide

e)

It reduces solubility

148.

What is the main form of oxygen transport in blood?

a)

Bound to hemoglobin within red blood cells

b)

Dissolved in plasma

c)

As carbonic acid

d)

Bound to albumin

e)

As carbon dioxide

149.

What role does hemoglobin play in oxygen diffusion gradients?

a)

It raises dissolved PO2 to increase diffusion

b)

It prevents oxygen release in tissues

c)

By binding oxygen, it keeps dissolved PO2 low in blood, maintaining the gradient for diffusion from alveoli

d)

It directly pumps oxygen across membranes

e)

It dissolves oxygen in plasma

150.

Which statement about oxygen solubility in blood is correct?

a)

Oxygen is highly soluble, so dissolved oxygen meets metabolic needs

b)

Oxygen has low solubility (~0.25 mL/100 mL blood), so hemoglobin is required

c)

Solubility is irrelevant to transport

d)

Solubility increases with more hemoglobin

e)

Solubility equals saturation

151.

Which effect would anemia (low hemoglobin concentration) have on arterial oxygen content and saturation?

a)

Decrease both content and saturation equally

b)

Increase content but decrease saturation

c)

Decrease oxygen content while saturation may remain normal

d)

No effect on content

e)

Increase dissolved oxygen to compensate fully

152.

Which parameter is least likely to change the oxygen content of arterial blood?

a)

Hemoglobin concentration

b)

Hemoglobin saturation

c)

Partial pressure of oxygen (PaO2) if extreme

d)

Presence of dyshemoglobins (carboxyhemoglobin, methemoglobin)

e)

Plasma sodium concentration

153.

Which of the following would increase arterial oxygen content at a given PaO2?

a)

Increased hemoglobin concentration

b)

Lower hemoglobin concentration

c)

Presence of carbon monoxide

d)

Right shift of dissociation curve only

e)

Higher alveolar water vapor

154.

How many peptide chains are in a hemoglobin molecule?

a)

4 (2α and 2β)

b)

2 (1α and 1β)

c)

3 (α, β, γ)

d)

5

e)

1 large chain

155.

Each hemoglobin molecule can bind how many oxygen molecules?

a)

1

b)

2

c)

4

d)

8

e)

None

156.

A patient with carbon monoxide poisoning has high measured oxygen saturation on pulse oximetry despite tissue hypoxia because:

a)

Carbon monoxide increases dissolved oxygen

b)

Carbon monoxide increases PO2

c)

Carboxyhemoglobin absorbs light similarly to oxyhemoglobin, falsely elevating SpO2

d)

Carbon monoxide increases hemoglobin concentration

e)

Pulse oximetry measures content, not saturation

157.

Which component of hemoglobin contains the iron atom that binds oxygen?

a)

Globin peptide chain

b)

Carbohydrate side chain

c)

Polypeptide tail

d)

Heme ring

e)

Lipid anchor

158.

Which is TRUE about hemoglobin structure?

a)

It contains five peptide chains

b)

Heme groups contain no metal

c)

It has four peptide chains, each associated with a heme containing iron

d)

It cannot bind carbon monoxide

e)

It is a single polypeptide

159.

What explains the sigmoid shape of the oxygen–hemoglobin dissociation curve?

a)

Cooperative binding of oxygen to hemoglobin

b)

Linear increase in solubility with PO2

c)

Saturation independent of PO2

d)

Irreversible binding at high PO2

e)

Because hemoglobin has only one binding site

160.

Which best describes the shape of the O2–Hb dissociation curve?

a)

Linear relationship

b)

Sigmoid (S-shaped) due to cooperative binding

c)

Inverse relationship

d)

No relationship

e)

Random fluctuation

161.

What is the main benefit of cooperative binding in hemoglobin?

a)

Facilitates uptake in lungs and release in tissues across a useful PO2 range

b)

Prevents any oxygen release

c)

Makes Hb nonfunctional at low PO2

d)

Increases dissolved O2 content

e)

Reduces affinity at all PO2

162.

Which is true about cooperative binding when the first O2 molecule binds to hemoglobin?

a)

Affinity of remaining sites increases, making next O2 easier to bind

b)

Affinity decreases for remaining sites

c)

All sites bind equally always

d)

Cooperativity prevents O2 release

e)

It causes irreversible saturation

163.

Which factor primarily causes the sigmoid nature of the O2–Hb curve at mid-range PO2?

a)

Cooperative interactions between subunits as O2 binds

b)

Linear Henry’s law solubility

c)

Bicarbonate buffering

d)

CO2 binding to Hb only

e)

Alveolar water vapor pressure

164.

Which of the following is a direct consequence of cooperative binding in hemoglobin during oxygen loading in lungs?

a)

Rapid increase in saturation with rising PO2 once the first O2 binds

b)

Slower saturation across all PO2 ranges

c)

Reduced oxygen content at high PO2

d)

Immediate O2 release in lungs

e)

No change in oxygen affinity

165.

A right shift in the O2–Hb dissociation curve indicates:

a)

Increased Hb affinity for O2

b)

Decreased Hb affinity for O2 (easier unloading)

c)

No change in affinity

d)

Complete loss of Hb function

e)

Increased arterial O2 content

166.

Which of the following causes a rightward shift of the dissociation curve?

a)

Decreased temperature

b)

Alkalosis (↑ pH)

c)

Increased CO2, increased H+, increased temperature, or ↑ 2,3-DPG

d)

Decreased 2,3-DPG

e)

Carbon monoxide binding only

167.

Which factor would shift the O2–Hb curve to the left?

a)

Decreased temperature

b)

Increased CO2

c)

Acidosis

d)

Increased 2,3-DPG

e)

Exercise

168.

Which of these is a direct effect of increased temperature on haemoglobin?

a)

Increased affinity for O2 (left shift)

b)

No change

c)

Decreased affinity for O2 (right shift)

d)

Irreversible O2 binding

e)

Reduced hemoglobin concentration

169.

What effect does a decrease in pH (acidosis) have on the O2–Hb dissociation curve?

a)

Shifts curve to the right (Bohr effect)

b)

Shifts curve to the left

c)

No effect

d)

Increases arterial PO2

e)

Increases hemoglobin concentration

170.

Which of the following does NOT shift the O2–Hb curve to the right?

a)

Increased CO2

b)

Increased temperature

c)

Decreased pH

d)

Decreased 2,3-DPG

e)

Exercise-induced factors

171.

Which variable is most likely to change oxygen unloading during fever?

a)

Increased hemoglobin concentration

b)

Increased temperature causing right shift and easier unloading

c)

Decreased pCO2

d)

Increased pH

e)

Lower 2,3-DPG

172.

Which of the following factors increases Hb’s affinity for O2?

a)

Decreased temperature

b)

Increased PCO2

c)

Increased H+ (low pH)

d)

Increased 2,3-DPG

e)

Exercise

173.

Which process increases oxygen unloading during exercise?

a)

Decrease in temperature

b)

Increased CO2, acidity, temperature and 2,3-DPG—right shift

c)

Increase in pH

d)

Decrease in 2,3-DPG

e)

Decrease in cardiac output

174.

What does a leftward shift of the O2–Hb dissociation curve imply for tissue oxygen delivery?

a)

Increased unloading to tissues

b)

Decreased affinity in lungs

c)

No change in oxygen binding

d)

Higher affinity—Hb holds O2 more tightly, making unloading to tissues harder

e)

Immediate hemoglobin breakdown

175.

Which mechanism best describes how increased 2,3-DPG affects oxygen delivery?

a)

It increases Hb affinity causing left shift

b)

It increases dissolved O2 directly

c)

It decreases Hb affinity causing right shift and enhances O2 release to tissues

d)

It blocks O2 binding irreversibly

e)

It changes atmospheric PO2

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