50 Most Important NEET PYQs of Chapter 17: Breathing and Exchange of Gases – Part 2 (Q26–50)
🔥 50 Most Important NEET PYQs of Chapter 17: Breathing and Exchange of Gases – Part 2 (Q26–50)
📚 By neetpyqall | biologyatease1.blogspot.com
Here's Part 2 of Chapter 17: Breathing and Exchange of Gases, featuring Q26 to Q50 with detailed explanations to help you conquer NEET!
26. In alveoli, the exchange of gases takes place through:
A) Osmosis
B) Active transport
C) Diffusion
D) Filtration
✅ Answer: C) Diffusion
🧠 Explanation: Gases move from higher to lower partial pressure by simple diffusion.
27. The volume of air remaining in the lungs after maximum forceful expiration is:
A) Inspiratory reserve volume
B) Functional residual capacity
C) Expiratory reserve volume
D) Residual volume
✅ Answer: D) Residual volume
🧠 Explanation: It keeps alveoli inflated and prevents lung collapse.
28. Which of the following will lead to decreased oxygen affinity of hemoglobin?
A) Low temperature
B) High pH
C) Low CO₂ concentration
D) High CO₂ concentration
✅ Answer: D) High CO₂ concentration
🧠 Explanation: This is due to the Bohr effect—more CO₂ reduces oxygen affinity.
29. Which of the following structures is not involved in respiration in human beings?
A) Nasal cavity
B) Pharynx
C) Larynx
D) Esophagus
✅ Answer: D) Esophagus
🧠 Explanation: Esophagus carries food, not air.
30. What is the partial pressure of oxygen in alveoli?
A) 104 mm Hg
B) 40 mm Hg
C) 95 mm Hg
D) 100 mm Hg
✅ Answer: A) 104 mm Hg
🧠 Explanation: Oxygen diffuses into blood from alveoli due to this pressure gradient.
31. The oxygen dissociation curve shifts to the right under:
A) Low CO₂, high pH
B) High CO₂, low pH
C) Low temperature
D) Low CO₂, low temperature
✅ Answer: B) High CO₂, low pH
🧠 Explanation: Promotes oxygen unloading at tissues.
32. Respiratory surface should have:
A) Moist surface
B) Less surface area
C) Thick walls
D) Low vascularization
✅ Answer: A) Moist surface
🧠 Explanation: Moist surface allows efficient gas exchange.
33. Vital capacity is:
A) IRV + ERV
B) IRV + TV + ERV
C) TV + RV
D) VC + RV
✅ Answer: B) IRV + TV + ERV
🧠 Explanation: It's the maximum amount of air exhaled after maximum inhalation.
34. Exchange of gases between blood and tissues is called:
A) Internal respiration
B) External respiration
C) Cellular respiration
D) Pulmonary ventilation
✅ Answer: A) Internal respiration
🧠 Explanation: Oxygen leaves blood and enters tissues; CO₂ does the opposite.
35. Which statement is true about hemoglobin?
A) It can carry only one molecule of O₂
B) It is not present in red blood cells
C) Each hemoglobin can bind four O₂ molecules
D) It binds only CO₂
✅ Answer: C) Each hemoglobin can bind four O₂ molecules
🧠 Explanation: Hemoglobin has 4 heme groups, each binds one O₂.
36. Intrapulmonary pressure during inspiration is:
A) Equal to atmospheric pressure
B) Greater than atmospheric pressure
C) Less than atmospheric pressure
D) Very high
✅ Answer: C) Less than atmospheric pressure
🧠 Explanation: This pressure drop allows air to enter the lungs.
37. Which among these has the highest affinity for oxygen?
A) Hemoglobin
B) Myoglobin
C) Haemocyanin
D) Chlorocruorin
✅ Answer: B) Myoglobin
🧠 Explanation: Myoglobin stores oxygen in muscles and binds it more tightly.
38. Which process is responsible for oxygen transport from lungs to tissues?
A) Diffusion
B) Hemolysis
C) Active transport
D) Osmosis
✅ Answer: A) Diffusion
🧠 Explanation: Oxygen moves passively based on pressure gradients.
39. How is most of the oxygen transported in the blood?
A) Dissolved in plasma
B) As bicarbonate
C) As oxyhemoglobin
D) As carbamino compound
✅ Answer: C) As oxyhemoglobin
🧠 Explanation: 97% of oxygen is bound to hemoglobin.
40. Inspiration occurs when:
A) Intrapulmonary pressure is equal to atmospheric pressure
B) Intrapulmonary pressure is less than atmospheric pressure
C) Diaphragm relaxes
D) Abdominal muscles contract
✅ Answer: B) Intrapulmonary pressure is less than atmospheric pressure
🧠 Explanation: Lower pressure in lungs pulls air in.
41. Pulmonary surfactant:
A) Increases surface tension
B) Reduces surface tension
C) Dries alveoli
D) Blocks oxygen diffusion
✅ Answer: B) Reduces surface tension
🧠 Explanation: It prevents alveoli from collapsing.
42. The normal respiratory rate in adult humans is:
A) 8–10 per minute
B) 12–16 per minute
C) 20–25 per minute
D) 30–35 per minute
✅ Answer: B) 12–16 per minute
🧠 Explanation: This is considered the normal resting rate.
43. In humans, expiration is normally:
A) Active
B) Passive
C) Voluntary
D) Enzymatic
✅ Answer: B) Passive
🧠 Explanation: Muscles relax, and air is pushed out due to recoil.
44. Hering-Breuer reflex prevents:
A) Excessive oxygenation
B) Excessive inspiration
C) Excessive CO₂ retention
D) Coughing
✅ Answer: B) Excessive inspiration
🧠 Explanation: Stretch receptors in lungs send signals to stop further inspiration.
45. Hypercapnia refers to:
A) Low CO₂ in blood
B) High CO₂ in blood
C) Low O₂ in blood
D) High O₂ in blood
✅ Answer: B) High CO₂ in blood
🧠 Explanation: Can stimulate increased breathing rate.
46. Respiratory quotient (RQ) for carbohydrates is:
A) 0.7
B) 1.0
C) 0.9
D) 1.2
✅ Answer: B) 1.0
🧠 Explanation: RQ = CO₂ produced / O₂ consumed = 1 for glucose.
47. Pneumotaxic center is located in:
A) Cerebellum
B) Pons
C) Medulla
D) Hypothalamus
✅ Answer: B) Pons
🧠 Explanation: It regulates the duration of inspiration.
48. Which cells secrete surfactant?
A) Type I alveolar cells
B) Type II alveolar cells
C) Ciliated cells
D) Goblet cells
✅ Answer: B) Type II alveolar cells
🧠 Explanation: They produce pulmonary surfactant.
49. Partial pressure of CO₂ in venous blood is:
A) 95 mm Hg
B) 40 mm Hg
C) 45 mm Hg
D) 104 mm Hg
✅ Answer: C) 45 mm Hg
🧠 Explanation: This higher pressure drives CO₂ into alveoli.
50. Which molecule binds CO more strongly than O₂?
A) Myoglobin
B) Hemoglobin
C) Albumin
D) Carbonic anhydrase
✅ Answer: B) Hemoglobin
🧠 Explanation: Carbon monoxide binds hemoglobin 200–250 times more strongly than oxygen.
✅ Part 2 complete – You’ve mastered Chapter 17 PYQs!
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