Q: According to Dalton's Law, what is the partial pressure of oxygen ($$P_{O_2$}) in $$dry atmospheric air at sea level, given that atmospheric pressure ($$P_{atm}) is 760 mm Hg $$and oxygen makes up 21% of the air?

$$P_{O_2$} = 760 \times 0.21 = 160 mm Hg$$

Q: A patient is breathing humidified air at 100% humidity and 37°C. If the atmospheric pressure is 760 mm Hg and the water vapor pressure ($$P_{H_2O}) is 47 mm Hg$$, what is the partial pressure of oxygen ($$P_{O_2$}) in $$the trachea?

$$P_{O_2$} = (760 - 47) \times 0.21 = 713 \times 0.21 = 150 mm Hg$$

Question 1

According to Dalton's Law, what is the partial pressure of oxygen ($$P_{O_2$}) in $$dry atmospheric air at sea level, given that atmospheric pressure ($$P_{atm}) is 760 mm Hg $$and oxygen makes up 21% of the air?

Accepted Answer

$$P_{O_2$} = 760 	imes 0.21 = 160 mm Hg$$

Question 2

A patient is breathing humidified air at 100% humidity and 37°C. If the atmospheric pressure is 760 mm Hg and the water vapor pressure ($$P_{H_2O}) is 47 mm Hg$$, what is the partial pressure of oxygen ($$P_{O_2$}) in $$the trachea?

Accepted Answer

$$P_{O_2$} = (760 - 47) 	imes 0.21 = 713 	imes 0.21 = 150 mm Hg$$

Question 3

Which of the following factors would most likely decrease the amount of oxygen reaching the alveoli for gas exchange?

Accepted Answer

Increased airway resistance

Question 4

According to Henry's Law, what determines the amount of a gas that dissolves in a liquid at a given temperature?

Accepted Answer

The partial pressure of the gas and its solubility in the liquid

Question 5

Why does carbon dioxide ($$CO_2) $$diffuse more readily in water than oxygen ($$O_2$$)?

Accepted Answer

$$CO_2 is 20 $$times more soluble in water than $$O_2$$

Question 6

During gas exchange in the lungs, which direction does oxygen ($$O_2) $$diffuse?

Accepted Answer

From the alveoli (higher $$P_{O_2$}) to $$the pulmonary capillaries (lower $$P_{O_2$})$$

Question 7

Which structural feature of the alveoli most enhances the rate of gas exchange?

Accepted Answer

Thin alveolar walls and close proximity to capillaries

Question 8

What is the main way oxygen is transported in the blood?

Accepted Answer

Bound to haemoglobin in red blood cells

Question 9

Which of the following would cause a rightward shift in the oxygen-haemoglobin dissociation curve, indicating decreased affinity of haemoglobin for oxygen?

Accepted Answer

Increased temperature

Question 10

Foetal haemoglobin has a higher affinity for oxygen than maternal haemoglobin. What is the physiological significance of this difference?

Accepted Answer

It enables oxygen to transfer from the mother to the foetus across the placenta

Question 11

Which of the following is NOT a method by which carbon dioxide ($$CO_2) is $$transported in the blood?

Accepted Answer

Bound to platelets

Question 12

A patient with anaemia has reduced oxygen-carrying capacity. Which factor is most directly responsible for this?

Accepted Answer

Decreased haemoglobin concentration

Question 13

During exercise, the oxygen-haemoglobin dissociation curve shifts to the right. What is the effect of this shift?

Accepted Answer

More oxygen is released to the tissues

Question 14

Which enzyme catalyzes the conversion of carbon dioxide and water to bicarbonate ions in red blood cells?

Accepted Answer

Carbonic anhydrase

Question 15

If the partial pressure of oxygen in the systemic capillaries is 100 mm Hg and in the tissue cells is 40 mm Hg, in which direction will oxygen diffuse?

Accepted Answer

From the systemic capillaries to the tissue cells

Question 16

Which of the following would most likely increase the rate of gas transfer between the alveoli and the blood?

Accepted Answer

Increasing alveolar surface area

Question 17

A climber at high altitude is experiencing hypoxia. Which factor is most responsible for the reduced oxygen availability?

Accepted Answer

Lower atmospheric pressure leading to lower $$P_{O_2$}$$

Question 18

Which of the following statements about gas exchange is correct?

Accepted Answer

Gas exchange occurs down a partial pressure gradient, from high to low pressure

Question 19

Which of the following would most likely cause acidosis in the blood?

Accepted Answer

High levels of $$CO_2$$ leading to increased production of $$H^+$$ ions

Question 20

A patient has a mutation that reduces the affinity of haemoglobin for oxygen. Which of the following would you expect to see in their oxygen-haemoglobin dissociation curve?

Accepted Answer

A rightward shift of the curve

Gas Exchange and Transport in the Respiratory System

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