Respiratory System Practice Questions

Q: Diffusion related to O2 transport across respiratory membrane is an example of?

Simple diffusion. ***Simple diffusion*** - Oxygen crosses the **respiratory membrane** (alveolar and capillary walls) directly through the lipid bilayer, driven by its **partial pressure gradient**. - This process does not require protein carriers or metabolic energy, fitting the definition of **simple diffusion**. *Facilitated diffusion* - This type of diffusion requires a **specific protein carrier** to transport molecules across the membrane. - While it does not require metabolic energy, oxygen transport across the respiratory membrane is efficient enough via simple diffusion due to its small size and lipid solubility. *Active diffusion* - This term is a **misnomer**; diffusion is by definition a passive process. - **Active transport** involves moving molecules against their concentration gradient, which requires metabolic energy (ATP). *Osmotic diffusion* - **Osmosis** specifically refers to the diffusion of **water** across a selectively permeable membrane. - It does not describe the movement of gases like oxygen.

Q: How does myoglobin respond to the Bohr effect compared to hemoglobin?

No effect on oxygen affinity. **No effect on oxygen affinity (Correct)** - Myoglobin has only one heme group, thus it **does not exhibit cooperativity** or allosteric regulation, unlike hemoglobin - The **Bohr effect**, which describes the pH and CO2-dependent changes in oxygen affinity, primarily applies to **hemoglobin's tetrameric structure** - Myoglobin's oxygen affinity **remains constant** regardless of pH or CO2 levels *Increased affinity for oxygen (Incorrect)* - This statement is incorrect because myoglobin's oxygen affinity is **already very high** and largely unaffected by the conditions that trigger the Bohr effect - The Bohr effect causes hemoglobin's affinity to *decrease* in acidic or high CO2 environments, facilitating oxygen release - Myoglobin does not exhibit this pH-dependent shift *Decreased affinity for oxygen (Incorrect)* - This would imply that myoglobin is sensitive to pH and CO2 levels in a way that promotes oxygen release, which is **not the case** - Myoglobin functions to **store oxygen** in muscles and release it only at very low partial pressures, independent of pH changes - Only hemoglobin shows decreased affinity under Bohr effect conditions *Same affinity for oxygen (Incorrect)* - This is incorrect because it suggests both molecules maintain the same affinity under varying conditions, which misunderstands the question - Hemoglobin's oxygen affinity **changes significantly** due to the Bohr effect (decreases with lower pH), whereas myoglobin's remains constant - The key distinction is that myoglobin has **no response** to Bohr effect conditions, not that it maintains the "same" affinity as hemoglobin

Q: Which of the following is a feature of pulmonary oxygen toxicity?

All of the options. ***All of the options*** - All three listed features are well-established manifestations of **pulmonary oxygen toxicity** - **Oxygen free radicals** generated during prolonged exposure to high O₂ concentrations cause synergistic damage affecting multiple cellular and physiological processes - The combination of these effects leads to significant **lung injury** and respiratory dysfunction **Why each option is correct:** **Increased capillary endothelial permeability:** - Oxygen free radicals directly damage endothelial cells, disrupting tight junctions - Results in **pulmonary edema** and impaired gas exchange - One of the earliest manifestations of O₂ toxicity **Decreased mucociliary transport in airways:** - High O₂ concentrations impair ciliated epithelial cell function - Alters mucus viscosity and composition - Reduces clearance of inhaled particles and pathogens, increasing risk of **respiratory infections** **Inhibition of phagocytosis function of alveolar macrophages:** - Alveolar macrophages are highly susceptible to oxidative stress - Impaired ability to phagocytose pathogens and cellular debris - Compromises the **lung's immune defense** and promotes inflammation

Q: Distending capacity of lung (maximum change in volume during inspiration) is maximum at?

Base of the lung. ***Base of the lung*** - Due to **gravitational forces**, the negative intrapleural pressure is less negative at the base compared to the apex, meaning the alveoli at the base are less stretched at rest. - This **lesser distension at rest** allows the alveoli at the base to have a greater capacity to expand and distend during inspiration, leading to better ventilation. *Apex of the lung* - The **more negative intrapleural pressure** at the apex causes alveoli to be more distended (larger) at functional residual capacity (FRC). - These already stretched alveoli have **less capacity to further distend** during inspiration, leading to less ventilation compared to the base. *Mid region of the lung* - The distending capacity in the mid-region is **intermediate** between the apex and the base. - It is **not the maximum** because the gravitational gradient of intrapleural pressure still allows the base to have a greater change in volume. *Lower lobe of the lung* - While the base of the lung is part of the lower lobe, referring specifically to the "lower lobe" is still **less precise** than the "base." - The specific term "base" refers to the region with the **largest distending capacity** due to the physiological pressure gradient.

Q: Functional residual capacity in normal adult is?

2400 ml. ***2400 ml*** - **Functional residual capacity (FRC)** is the volume of air remaining in the lungs after a normal passive exhalation. - In a healthy adult, the average FRC is approximately **2400 mL**, or 2.4 liters. *500 ml* - This volume typically represents the **tidal volume (TV)**, which is the amount of air exchanged during normal, quiet breathing. - Tidal volume is a much smaller component of lung capacity compared to FRC. *1200 ml* - This value is close to the **residual volume (RV)**, which is the amount of air remaining in the lungs after a maximal forceful exhalation. - FRC is the sum of expiratory reserve volume and residual volume, thus larger than RV alone. *3200 ml* - This value is closer to the **inspiratory capacity (IC)**, which is the maximum volume of air that can be inspired after a normal expiration. - Alternatively, it could be closer to the **vital capacity (VC)**, which is typically around 4500-5000 mL in healthy adults, making 3200 mL still too low for VC and too high for FRC.

Q: Which of the following statements is true about the Bohr effect?

Decrease affinity of O2 by increase PCO2. ***Decrease affinity of O2 by increase PCO2*** - The **Bohr effect** describes how an increase in **PCO2** (carbon dioxide partial pressure) or a decrease in pH (more acidic environment) reduces hemoglobin's affinity for oxygen. - This is the most complete statement, as increased PCO2 leads to increased H+ (via CO2 + H2O → H2CO3 → H+ + HCO3-), which binds to hemoglobin and reduces oxygen affinity. - This facilitates oxygen release to metabolically active tissues producing more CO2 and H+. - Causes a **right shift** of the oxygen-hemoglobin dissociation curve. *Left shift of Hb-O2 dissociation curve* - A **left shift** indicates *increased* affinity of hemoglobin for oxygen (seen with decreased PCO2, increased pH, decreased temperature, or decreased 2,3-BPG). - The Bohr effect causes a **right shift**, not a left shift, signifying *decreased* oxygen affinity and promoting oxygen release to tissues. - This option is the opposite of what occurs in the Bohr effect. *It is due to H+.* - While **H+ ions** are indeed the molecular mechanism of the Bohr effect (H+ binds to histidine residues on hemoglobin, stabilizing the deoxygenated T-state), this statement alone is incomplete. - It doesn't mention the physiological trigger (increased PCO2) or the functional consequence (decreased O2 affinity). - The first option is more comprehensive and better describes the complete Bohr effect phenomenon. *All are true* - This is incorrect because the statement about a **left shift** is definitively false. - The Bohr effect produces a *right shift*, not a left shift, of the Hb-O2 dissociation curve.

Q: Where does the respiratory exchange of gases begin?

Bronchiole. ***Correct: Bronchiole (Respiratory Bronchioles)*** - The **respiratory zone** where gas exchange begins starts at the **respiratory bronchioles** - Respiratory bronchioles have **occasional alveoli** budding from their walls, marking the first site where oxygen and carbon dioxide exchange occurs - This represents the **transition** from the conducting zone (which only transports air) to the respiratory zone (where gas exchange happens) - According to standard respiratory physiology, the respiratory zone includes: respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli *Incorrect: Alveoli* - While **alveoli** are the **primary and most efficient** site of gas exchange due to their enormous surface area (~70 m²) and thin walls - They are NOT where gas exchange "begins" - gas exchange has already started in the respiratory bronchioles - Alveoli represent the terminal and most developed part of the respiratory zone where the majority of gas exchange occurs *Incorrect: Bronchi* - **Bronchi** are part of the **conducting zone** of the respiratory system - Their walls are too thick and they lack alveoli, so **no gas exchange** occurs here - Their function is to conduct air to and from the lungs, with mucus and cilia helping to filter particles *Incorrect: Tissue level* - **Tissue level** gas exchange refers to **internal/systemic respiration** - the exchange of gases between blood and body tissues - This occurs in systemic capillaries throughout the body, NOT in the lungs - The question asks about where respiratory exchange begins in the lungs (external respiration), not tissue-level gas exchange

Q: Which of the following statements about the O2-Hb dissociation curve is correct?

It demonstrates cooperative binding.. ***It demonstrates cooperative binding.*** - **Cooperative binding** describes how the binding of one oxygen molecule to hemoglobin increases the affinity of the remaining binding sites for oxygen. - This property gives the O2-Hb dissociation curve its characteristic **sigmoid (S-shaped)** appearance, allowing for efficient oxygen loading in the lungs and unloading in the tissues. *The curve is a straight line.* - The O2-Hb dissociation curve is **sigmoid or S-shaped**, not a straight line, due to the phenomenon of cooperative binding. - A straight line would imply a constant affinity of hemoglobin for oxygen, which is not the case. *It is 100% saturated at a PO2 of 100 mmHg.* - Hemoglobin is typically around **97-98% saturated** at a PO2 of 100 mmHg (arterial blood). - Complete 100% saturation is rarely achieved under physiological conditions. *A hemoglobin molecule can carry 4 molecules of O2.* - While this statement is factually true (one hemoglobin molecule has **four heme groups** and can bind up to **four molecules of oxygen**), it describes the structure and oxygen-carrying capacity of hemoglobin rather than a characteristic of the dissociation **curve itself**. - The question asks about features of the O2-Hb dissociation curve, and cooperative binding is the key property that defines the curve's behavior and sigmoid shape.

Question 1

Diffusion related to O2 transport across respiratory membrane is an example of?

Accepted Answer

Simple diffusion

Answer

Facilitated diffusion

Answer

Active diffusion

Answer

Osmotic diffusion

Question 2

What is the primary graphical difference between the Hb-O2 dissociation curve and the Hb-CO curve?

Accepted Answer

The Hb-CO curve is shifted to the left compared to the Hb-O2 curve.

Answer

CO has a higher affinity for hemoglobin than oxygen.

Answer

None of the options.

Answer

CO binding prevents normal oxygen release despite high oxygen saturation

Question 3

How does myoglobin respond to the Bohr effect compared to hemoglobin?

Accepted Answer

No effect on oxygen affinity

Answer

Increased affinity for oxygen

Answer

Decreased affinity for oxygen

Answer

Same affinity for oxygen

Question 4

Which of the following is a feature of pulmonary oxygen toxicity?

Accepted Answer

All of the options

Answer

Decreased mucociliary transport in airways

Answer

Increased capillary endothelial permeability

Answer

Inhibition of phagocytosis function of alveolar macrophages

Question 5

Distending capacity of lung (maximum change in volume during inspiration) is maximum at?

Accepted Answer

Base of the lung

Answer

Apex of the lung

Answer

Mid region of the lung

Answer

Lower lobe of the lung

Question 6

Functional residual capacity in normal adult is?

Accepted Answer

2400 ml

Answer

500 ml

Answer

1200 ml

Answer

3200 ml

Question 7

Which of the following statements is true about the Bohr effect?

Accepted Answer

Decrease affinity of O2 by increase PCO2

Answer

All are true

Answer

Left shift of Hb-02 dissociation curve

Answer

It is due to H+.

Question 8

What is the maximum voluntary ventilation (MVV) and how does it relate to respiratory function?

Accepted Answer

Maximum amount of air that can be inspired and expired in one minute

Answer

Amount of air expired in one minute at rest

Answer

Maximum amount of air that can be inspired per breath

Answer

Maximum amount of air remaining in lung after forced expiration

Question 9

Where does the respiratory exchange of gases begin?

Accepted Answer

Bronchiole

Answer

Bronchi

Answer

Alveoli

Answer

Tissue level

Question 10

Which of the following statements about the O2-Hb dissociation curve is correct?

Accepted Answer

It demonstrates cooperative binding.

Answer

The curve is a straight line.

Answer

It is 100% saturated at a PO2 of 100 mmHg.

Answer

A hemoglobin molecule can carry 4 molecules of O2.

Respiratory System — MCQs

Respiratory System — MCQs

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