Gaseous Exchange in Humans – 25 Most Important MCQs with Answers

Preparing for MDCAT, PPSC, and other competitive exams? Here are the 25 most repeated MCQs on Gaseous Exchange in Humans with correct answers to help you revise quickly.

MCQs on Gaseous Exchange in Humans

1. Site of gaseous exchange in human lungs is:
A) Bronchi
B) Bronchioles
C) Alveoli ✅
D) Trachea

2. Which structure increases the surface area for gaseous exchange?
A) Alveoli ✅
B) Bronchi
C) Pleura
D) Diaphragm

3. Main muscle involved in inspiration is:
A) Diaphragm ✅
B) Intercostal muscles
C) Abdominal muscles
D) Sternum

4. Oxygen transport in blood is mainly through:
A) Plasma
B) Hemoglobin ✅
C) WBC
D) Platelets

5. Normal breathing rate in adults at rest is:
A) 6–8 per minute
B) 12–18 per minute ✅
C) 20–25 per minute
D) 30–35 per minute

6. The process of taking in oxygen and releasing carbon dioxide is called:
A) Respiration ✅
B) Photosynthesis
C) Excretion
D) Digestion

7. Hemoglobin combines with oxygen to form:
A) Carboxyhemoglobin
B) Oxyhemoglobin ✅
C) Carbaminohemoglobin
D) Myoglobin

8. CO₂ is mainly transported in blood as:
A) Dissolved CO₂
B) Carbaminohemoglobin
C) Bicarbonate ions ✅
D) Carbonic acid

9. Exchange of gases between blood and body tissues is called:
A) Internal respiration ✅
B) External respiration
C) Cellular respiration
D) Ventilation

10. Which enzyme helps in rapid conversion of CO₂ into bicarbonate in RBCs?
A) Amylase
B) Carbonic anhydrase ✅
C) Lipase
D) Pepsin

11. Which part of brain controls breathing?
A) Cerebrum
B) Medulla oblongata ✅
C) Cerebellum
D) Hypothalamus

12. Inspiration occurs when diaphragm:
A) Relaxes
B) Contracts ✅
C) Becomes rigid
D) Moves upward

13. Which of the following decreases during expiration?
A) Lung volume ✅
B) Pressure in lungs
C) Air pushed out
D) Alveolar recoil

14. Partial pressure of oxygen in alveoli is about:
A) 40 mmHg
B) 100 mmHg ✅
C) 140 mmHg
D) 200 mmHg

15. Total surface area of alveoli in human lungs is approximately:
A) 5 m²
B) 50 m²
C) 70 m² ✅
D) 200 m²

16. Respiratory pigment in humans is:
A) Hemocyanin
B) Hemoglobin ✅
C) Myoglobin
D) Chlorophyll

17. Pneumonia primarily affects:
A) Alveoli ✅
B) Trachea
C) Pleura
D) Diaphragm

18. Oxygen dissociation curve of hemoglobin is:
A) Linear
B) Sigmoid (S-shaped) ✅
C) Exponential
D) Hyperbolic

19. Which factor decreases affinity of hemoglobin for oxygen?
A) Low temperature
B) High CO₂ concentration ✅
C) Low H⁺ concentration
D) Low 2,3-BPG

20. Normal tidal volume in adult humans is:
A) 100 ml
B) 300 ml
C) 500 ml ✅
D) 1500 ml

21. Which structure prevents food from entering trachea during swallowing?
A) Glottis
B) Epiglottis ✅
C) Larynx
D) Uvula

22. Which gas has the highest diffusion rate?
A) O₂
B) CO₂ ✅
C) N₂
D) H₂

23. Hyperventilation leads to:
A) Increase in CO₂ in blood
B) Decrease in CO₂ in blood ✅
C) Increase in O₂ in blood
D) No effect

24. Which condition results from deficiency of surfactant in lungs?
A) Asthma
B) Emphysema
C) Respiratory distress syndrome ✅
D) Bronchitis

25. Smoking damages gaseous exchange by destroying:
A) Alveoli ✅
B) Diaphragm
C) Trachea
D) Bronchioles

✅ These MCQs are highly repeated in PPSC, MDCAT, and entry tests. Practice them well to boost you

Comments

Post a Comment

Popular posts from this blog

Image
  Smart Bio Notes"Hand-Drawn Chloroplast Diagram + Easy Explanation – Watch Now! 🎥" 🔬  What is a Chloroplast? "Chlorophyll is the green color in plants that acts like a solar panel, capturing sunlight to help the plant make its own food through photosynthesis." INTRODUCTION Chlorophyll is a green pigment found in plants, algae, and some bacteria. It is located in the chloroplasts of plant cells. Chlorophyll is essential for photosynthesis , the process by which plants make food. It absorbs sunlight , mainly blue and red light, and reflects green light (which is why plants look green). There are different types of chlorophyll , like chlorophyll a and b , with chlorophyll a being the most common. In this blog, we’ll explore the structure, function, and importance of chloroplasts with a detailed hand-drawn diagram to make learning easy for your exams and fun! 🎨📚 📌 Where Are Chloroplasts Found? Chloroplast has chlorophyll that is green in color thats why...
Read more
Image
"Cell Membrane: The Ultimate Protective Shield of Life – Structure, Functions & Importance" 🚀🔬 The cell membrane , also known as the plasma membrane , is an essential component of all living cells. It serves as a protective barrier , controlling what enters and exits the cell while maintaining a stable internal environment. Without it, cells would not be able to function properly! Structure of the Cell Membrane The cell membrane follows the fluid mosaic model , meaning it is flexible and consists of multiple components working together. Its structure includes: Phospholipid Bilayer : Two layers of molecules that form the boundary of the cell. The top circles are hydrophilic heads (water loving), and the tails inside are hydrophobic (water fearing). this keeps the cell safe! Proteins : Various proteins are embedded in the membrane, acting as channels.These are like tiny doors that control what enters and leaves the cell. Cholesterol : This molecule helps prevent cell mem...
Read more
Image
"How Mitochondria Keep You Alive – The Science of Cellular Energy! 🧬🔥" Mitochondria, the energy factory of your body, are fascinating organelles found in nearly all eukaryotic cells. Known as the powerhouse of the cell , mitochondria generate energy in the form of ATP (adenosine triphosphate), which is essential for various cellular activities.These tiny organelles convert glucose & oxygen into ATP (energy) , keeping every cell in your body alive and functioning! Let’s dive deeper into the structure, function, and importance of mitochondria in biological systems. Structure of Mitochondria Here’s the structure of mitochondria explained in easy points: Double Membrane : Mitochondria have two membranes: Outer membrane – smooth and surrounds the organelle. Inner membrane – folded into cristae, increasing surface area. Cristae : These are the folds of the inner membrane where energy (ATP) is produced. Matrix : The space inside the inner membrane; conta...
Read more