Breathing And Exchange Of Gases Module

Q1. In humans, what is true about RBCs?

1. They transport about 80% of oxygen, and the remaining 20% is dissolved in blood plasma.
2. They transport 99.5% of oxygen
3. About 20-25% of CO2 is carried by them
4. CO2 is not held by them

Answer – 2, They transport 99.5% of oxygen
Explanation: Red blood cells (RBCs) transport 99.5% of Oxygen and carry about 20-25% of Carbon Dioxide (CO2). The remaining 0.5% of oxygen is transported in the dissolved state in blood plasma, while the rest of the CO2 is exhaled during respiration.

Q2. Pick the incorrect statement

1. A bird’s ability to breathe efficiently is enhanced by the presence of non-respiratory air sacs.
2. Having residual air in the lungs slightly reduces the efficiency of respiration in mammals.
3. Fishes use counter-current flow to facilitate efficient respiration.
4. In insects, circulating body fluids help distribute oxygen to the tissues.

Answer – 2, Having residual air in the lungs slightly reduces the efficiency of respiration in mammals.
Explanation: This statement is incorrect because residual air in the lungs improves the efficiency of respiration in mammals. The residual air volume refers to the air that remains in the lungs after a complete exhalation. It serves an essential purpose by ensuring a continuous supply of fresh oxygen to the lungs during the respiratory cycle.

During normal breathing, the lungs are never completely empty of air, and the residual volume helps maintain a favorable gradient for gas exchange. This residual air, rich in oxygen, mixes with incoming fresh air during inhalation, facilitating the efficient exchange of gases in the alveoli of the lungs.

Additionally, the residual volume plays a role in preventing lung collapse and maintaining lung elasticity, which is necessary for proper respiratory function.

Therefore, having residual air in the lungs does not reduce the efficiency of respiration in mammals; it contributes to its effectiveness.

Q3. Why does oxygen move through the alveolar blood capillaries of the lungs?

1. Differences in the O2 tension and partial pressure of these chambers
2. The partial pressure of CO2
3. Union of O2 with hemoglobin
4. All of the above

Answer – 4, All of the above
Explanation: Oxygen diffuses through the alveolar blood capillaries of the lungs due to a difference in the partial pressure of oxygen and carbon dioxide. In red blood cells, oxygen combines with hemoglobin molecules.

Q4. Partial Pressure of oxygen is equal to

1. Deoxygenated Blood and tissues
2. Alveoli and Oxygenated Blood
3. Alveoli and Deoxygenated Blood
4. Air and Alveoli

Answer – 2, Alveoli and Oxygenated Blood
Explanation: In the context of oxygen (O2) in the respiratory system, the partial pressure of oxygen refers to the pressure exerted by oxygen molecules in a given area.

In the lungs, oxygenated blood from the pulmonary circulation returns to the heart and is pumped to various tissues and organs throughout the body. In the alveoli of the lungs, where gas exchange occurs, oxygen from inhaled air diffuses into the alveolar space, equilibrium with the partial pressure of oxygen in the alveoli.

This equilibrated oxygen binds to hemoglobin in red blood cells, forming oxygenated blood. The partial pressure of oxygen in the alveoli and oxygenated blood is equal because they are nearby during the gas exchange process.

Q5. A person living at sea level has approximately 5 million red blood cells per cubic millimeter of blood. In comparison, a person living at 5400 meters has about 8 million red blood cells. Because of the high altitude

1. Low O2 content in the atmosphere requires more red blood cells to absorb the O2 amount needed for survival.
2. more UV light and increased red blood cell production;
3. people eat more nutritious food, so more red blood cells are formed
4. people are pollution- free-breathing air and more oxygen available

Answer – 2, UV light and increased red blood cell production
Explanation: At higher altitudes, the thin atmosphere contains less oxygen. This low oxygen content increases the body’s need for red blood cells to absorb the oxygen needed for survival. Therefore, the body produces more red blood cells to make up for this need, resulting in more red blood cells per cubic millimeter.

Q6. An increase in lung ventilation rate is caused by which of the following conditions?

1. Increase of CO2 content in inhaled air
2. Addition of CO2 content in exhaled air
3. Decrease of O2 content in exhaled air
4. Reduction of O2 content in inhaled air

Answer – 1, Increase of CO2 content in inhaled air
Explanation: The increase in carbon dioxide (CO2) levels triggers an increase in the lung ventilation rate as it signals a need for more oxygen to be obtained. This leads to an increased demand for oxygen, which increases respiratory rate and depth.

Q7. Haemoglobin is bonded to carbon monoxide and, therefore cannot transport oxygen is called

1. Carboxyhaemoglobin
2. Reduced hemoglobin
3. Carbamino Haemoglobin
4. Methemoglobin

Answer – 1, Carboxyhaemoglobin
Explanation: Carboxyhaemoglobin is formed when hemoglobin is bonded to carbon monoxide, which prevents it from transporting oxygen. This results in less oxygen being available for cells and tissues, leading to symptoms of oxygen deprivation such as headaches and dizziness.

Q8. What diseases can occur when the hemoglobin concentration in the blood is low?

1. Pleurisy
2. Emphysema
3. Anemia
4. pneumonia

Answer- 3, Anemia
Explanation: In anemia, the number of red blood cells or the amount of hemoglobin in the blood decreases. Hemoglobin is the protein responsible for carrying oxygen to the body’s tissues. When the hemoglobin content decreases, the blood’s ability to transport oxygen is impaired, leading to symptoms such as fatigue, weakness, shortness of breath, pale skin, and other related manifestations.

Pleurisy, emphysema, and pneumonia are all different respiratory conditions and are not directly related to a decrease in hemoglobin content in the blood. Pleurisy refers to inflammation of the pleura (the thin membranes that line the lungs and chest cavity), emphysema is a chronic lung disease characterized by damage to the air sacs, and pneumonia is an infection or inflammation of the lungs caused by various pathogens.

Q9. Mark incorrect statements about respiratory system function.

1. Humidify the air
2. warm the air
3. Diffusion of gas
4. purify the air

Answer – 4, purify the air
Explanation: All the statements are correct except for purifying the air. The respiratory system does not clarify the air, but instead filters and humidifies it so that oxygen can be delivered to the body.

Q10. Among the following which is made up of cartilage

1. Larynx
2. Pharynx
3. Cartilage
4. Trachea

Answer – 4, trachea
Explanation: The correct answer is the trachea, which is made up of cartilage. The larynx, pharynx, and nasal septum are all made of different materials and therefore not the right option.

Q11. What happens to the respiratory rate when the carbon dioxide concentration in the blood increases?

1. remain unaffected;
2. decrease
3. stop
4. increase

Answer- 4, increase
Explanation: When the carbon dioxide concentration in the blood increases, the respiratory rate will also increase to expel the excess carbon dioxide. This response is known as hyperventilation and is triggered by an increased level of CO2 in the body.

Q12. When blood carbon dioxide levels rise, what happens to breathing?

What if the concentration of O2 in the tissues is high near the respiratory surface?

1. oxyhemoglobin dissociates to supply O2 to tissues
2. hemoglobin will combine with more O2 for tissues
3. oxyhemoglobin will not dissociate to provide O2 to tissues
4. CO2 will interfere with O2 transport.

Answer – 3, hemoglobin will combine with more O2 for tissues
Explanation: When blood carbon dioxide levels rise, breathing rate increases. If the concentration of O2 is high near the respiratory surface then hemoglobin will combine with more O2 for the tissues. Oxyhemoglobin will still dissociate to provide O2 to tissues, however, CO2 will interfere with O2 transport.

When blood carbon dioxide (CO2) levels rise, it leads to changes in breathing.

When the concentration of oxygen in the tissues is high, oxyhemoglobin (an oxygen-bound form of hemoglobin) readily dissociates, releasing oxygen to supply the tissues with the necessary oxygenation. This occurs due to the pressure gradient between the oxygen-rich tissues and the oxygen-poor blood, promoting oxygen release from hemoglobin.

Q13. Where does the motivation for voluntary forced breathing come from?

1. marrow
2. vagus nerve
3. spinal cord
4. Brain

Answer – 4, brain
Explanation: The motivation for voluntary forced breathing comes from the brain. It is the brain that sends signals to the muscles in the chest and abdomen to contract and expand, resulting in breathing. This is also known as diaphragmatic breathing.

Q14. What if human blood becomes acidic (low pH)?

1. The oxygen-carrying capacity of hemoglobin is reduced
2. The oxygen-carrying capacity of hemoglobin is increased
3. Increased red blood cell count
4. Decreased red blood cell count

Answer – 1, The oxygen-carrying capacity of hemoglobin is reduced
Explanation: The oxygen-carrying capacity of hemoglobin is decreased. When the pH of human blood decreases, it becomes more acidic and the oxygen-carrying capacity of hemoglobin is reduced due to changes in its structure. This can lead to a decrease in red blood cell count as well.

Q15. Does the polluted air contain unusually high concentrations inhaled by the patient?

1. carbon disulfide
2. chloroform
3. carbon dioxide
4. carbon monoxide gas

Answer – 4, carbon monoxide gas
Explanation: When a patient inhales polluted air containing an unusually high concentration of carbon monoxide (CO), it can have detrimental effects on their health. Carbon monoxide is a toxic gas that is produced by the incomplete combustion of fossil fuels, such as in car exhaust or faulty heating systems.

When carbon monoxide is inhaled, it binds strongly to hemoglobin in red blood cells, forming carboxyhemoglobin. This binding reduces the oxygen-carrying capacity of the blood, leading to a decreased supply of oxygen to the body’s tissues. This lack of oxygen can result in symptoms ranging from mild, such as headache and dizziness, to severe, including organ damage or even death in extreme cases.

Q16. C02 in the blood lowers the pH because C02 combines with ______, and the reaction rate increases ______.

1. H2O to form H+ and HCO3-, carbonic anhydrase
2. H2O forms only HCO3-, carbonic anhydrase
3. H2O only forms H+ ions, carbon
4. H+ to form HCO3-, oxyhemoglobin

Answer – 1, H2O to form H+ and HCO3-, carbonic anhydrase
Explanation: In the blood, carbon dioxide (CO2) dissolves and combines with water (H2O) to form carbonic acid (H2CO3). A reaction facilitated by an enzyme called carbonic anhydrase increases the rate of the reaction by releasing hydrogen ions (H+) and bicarbonate ions (HCO3-). Carbonic acid is then dissociated into hydrogen ions (H+) and bicarbonate ions (HCO3-).

The increased concentration of hydrogen ions from the dissociation of carbonic acid lowers the pH of the blood, making it more acidic. This pH change is important for maintaining the acid-base balance in the body.