🔬 Biology · Class 11 · NEET
Breathing and Exchange of Gases - Practice Questions with Answers 75 free MCQs on Breathing and Exchange of Gases, each with its own worked answer and explanation. The mechanics of breathing, lung volumes, gas transport in blood, the Bohr effect, and respiratory regulation.
Take the timed Breathing and Exchange of Gases chapterwise test → 75 practice questions on Breathing and Exchange of Gases , sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Breathing and Exchange of Gases notes .
O₂-Haemoglobin Dissociation Curve pO₂ % Hb saturated resting curve shifted RIGHT (Bohr effect: ↑CO₂, ↑H⁺, ↑temperature) Sigmoid shape = cooperative binding; right-shift means O₂ is released more easily in active tissue The S-shaped (sigmoid) curve reflects cooperative binding between Hb's four O₂ sites; the Bohr effect shifts the whole curve to the right under conditions found in actively respiring tissue (more CO₂, more acid, more heat), making haemoglobin release oxygen more readily exactly where it's needed.
Easy - 25 questions Q1.
The C-shaped cartilaginous rings that keep the trachea from collapsing are made of:
A Hyaline cartilageB BoneC Elastic fibresD Smooth muscleShow answer & explanation →
Q2.
The flap of tissue that prevents food from entering the wind pipe during swallowing is the:
A EpiglottisB GlottisC UvulaD PharynxShow answer & explanation →
Q3.
The additional volume of air a person can breathe in forcefully over and above the tidal volume is the:
A Expiratory reserve volumeB Residual volumeC Inspiratory reserve volumeD Vital capacityShow answer & explanation →
Q5.
The muscles present between the ribs that assist in breathing are the:
A Intercostal musclesB Pectoral musclesC Abdominal musclesD Cardiac musclesShow answer & explanation →
Q7.
Breathing in (inhalation) is caused by the diaphragm:
A Relaxing and moving upB Contracting and moving downC Staying stillD Moving sidewaysShow answer & explanation →
Q8.
The respiratory pigment found in human red blood cells is:
A ChlorophyllB HemocyaninC MyoglobinD HemoglobinShow answer & explanation →
Q9.
The pleural membrane that directly covers the lung surface is the:
A PericardiumB Parietal pleuraC Visceral pleuraD PeritoneumShow answer & explanation →
Q10.
The conducting part of the human respiratory system includes the:
A Diaphragm, ribs and intercostal muscles under typical physiological conditionsB Alveoli, alveolar ducts and alveolar sacs in most observed casesC Pulmonary artery, vein and capillary bed according to standard textsD Nasal passage, pharynx, larynx, trachea and bronchiShow answer & explanation →
Q11.
Most of the carbon dioxide transported in blood is carried as:
A Bicarbonate ionsB Carbonic acid crystalsC Dissolved gas in plasmaD CarbaminohemoglobinShow answer & explanation →
Q12.
The volume of air that remains in the lungs even after a forceful exhalation is called:
A Inspiratory reserve volumeB Tidal volumeC Residual volumeD Vital capacityShow answer & explanation →
Q13.
Exhalation (expiration) occurs mainly because the volume of the thoracic cavity:
A Decreases as the diaphragm and intercostal muscles relaxB Increases as the diaphragm contracts downwardC Increases due to outward movement of the rib cageD Stays roughly constant while internal pressure risesShow answer & explanation →
Q14.
The exchange of O<sub>2</sub> and CO<sub>2</sub> between alveoli and blood occurs mainly by:
A Active transport across alveolar wallsB Facilitated transport using carrier proteinsC Bulk flow driven by blood pressureD Simple diffusion along a pressure gradientShow answer & explanation →
Q15.
The rhythm of breathing in humans is primarily controlled by a centre located in the:
A Medulla oblongata, in the brainstemB Cerebrum, in the frontal regionC Cerebellum, behind the brainstemD Spinal cord, near the cervical regionShow answer & explanation →
Q16.
The exchange of gases between an organism and its surroundings is called:
A respirationB digestionC circulationD excretionShow answer & explanation →
Q19.
The gas given out of the body during breathing is:
A carbon dioxideB pure oxygenC pure nitrogenD light heliumShow answer & explanation →
Q22.
The muscular sheet below the lungs that aids breathing is the:
A diaphragmB the liverC the stomachD the heartShow answer & explanation →
Medium - 25 questions Q26.
Vital capacity is best defined as the maximum volume of air a person can breathe out after:
A A normal inspirationB A forced inspirationC A normal expirationD Holding the breathShow answer & explanation →
Q27.
Functional residual capacity of the lungs is the sum of:
A TV and IRVB IRV and ERVC TV and RVD ERV and RVShow answer & explanation →
Q28.
Carbon dioxide is carried as bicarbonate because the enzyme carbonic anhydrase in red blood cells speeds up its combination with:
A OxygenB SodiumC WaterD Plasma proteinShow answer & explanation →
Q29.
When CO<sub>2</sub> enters the red blood cell and is converted to bicarbonate, the outward movement of HCO<sub>3</sub><sup>-</sup> is balanced by inward movement of chloride, a phenomenon called:
A Bohr effectB Chloride shiftC Haldane effectD Root effectShow answer & explanation →
Q31.
During the Bohr effect, increased CO<sub>2</sub> in blood:
A Raises hemoglobin's affinity for O<sub>2</sub> by stabilizing the relaxed conformationB Decreases hemoglobin affinity for O<sub>2</sub> (more O<sub>2</sub> released to active tissues)C Leaves the oxygen-hemoglobin binding curve completely unshiftedD Denatures hemoglobin's quaternary structure within red blood cellsShow answer & explanation →
Q32.
Tidal volume is:
A The maximum air volume the lungs can hold after forced inhalationB Volume of air inhaled/exhaled in a normal breath (~500 mL)C The air remaining in lungs after the most forceful possible exhalationD The maximum air that can be exhaled after the deepest possible inhalationShow answer & explanation →
Q33.
Surfactant in alveoli prevents:
A Gas exchange across the alveolar membrane surfaceB Alveoli collapse by reducing surface tensionC Infection from inhaled bacteria and airborne pathogensD Blood clotting occurring within the lung capillary networkShow answer & explanation →
Q34.
Carbon dioxide is transported in blood mainly as:
A Dissolved CO<sub>2</sub> in plasma, accounting for the majority of transported gasB Carbaminohemoglobin formed by binding to globin chains exclusivelyC Bicarbonate ions (HCO<sub>3</sub><sup>-</sup>) in plasma (~70%)D Carbonic acid accumulating freely in plasma without further dissociationShow answer & explanation →
Q35.
Residual volume refers to the volume of air that:
A Can be forcibly exhaled after a normal tidal expirationB Is inhaled or exhaled during normal quiet breathingC Remains in the lungs even after the most forceful expirationD Can be additionally inhaled after a normal tidal inspirationShow answer & explanation →
Q36.
Most of the oxygen transported in the blood is carried:
A Bound to plasma albumin proteins according to standard textsB Dissolved directly in blood plasma in most observed casesC As bicarbonate ions in plasma under typical physiological conditionsD Bound to haemoglobin within red blood cellsShow answer & explanation →
Q37.
The partial pressure of oxygen is higher in the alveoli than in the pulmonary capillary blood arriving at the lungs. This pressure difference causes oxygen to:
A Diffuse from the blood into the alveoliB Remain in the alveoli without net movementC Diffuse from the alveoli into the bloodD Bind irreversibly to carbon dioxide in the alveolar airShow answer & explanation →
Q38.
Contraction of the diaphragm during inspiration causes it to:
A Pull the lungs downward without changing thoracic volumeB Dome upward, decreasing the volume of the thoracic cavityC Remain stationary while the rib cage does all the workD Flatten, increasing the volume of the thoracic cavityShow answer & explanation →
Q39.
Hyperventilation can lead to a drop in blood CO<sub>2</sub> levels, which in turn causes:
A A rise in blood pH, since less carbonic acid is formedB Increased binding of CO<sub>2</sub> to haemoglobin as carbaminohaemoglobinC No change in pH, since CO<sub>2</sub> does not affect blood acidityD A fall in blood pH, due to excess bicarbonate accumulationShow answer & explanation →
Q40.
Which respiratory centre, located in the medulla, primarily sets the basic rhythm of breathing?
A Medullary rhythm/respiratory centreB Carotid body chemoreceptorsC Aortic body chemoreceptorsD Pneumotaxic centre in the ponsShow answer & explanation →
Q41.
Oxygen is transported in the blood mainly bound to:
A haemoglobinB only the plasmaC white blood cellsD the plateletsShow answer & explanation →
Q42.
Gas exchange in the lungs takes place by the process of:
A diffusionB active transportC filtrationD osmosisShow answer & explanation →
Q43.
The two tubes that branch from the trachea into the lungs are the:
A bronchiB bronchiolesC alveoliD laryngesShow answer & explanation →
Q44.
During inhalation, the diaphragm:
A contracts and flattensB relaxes and domes upC disappears entirelyD stops all movementShow answer & explanation →
Q45.
Most carbon dioxide is carried in the blood in the form of:
A bicarbonate ionsB only free gasC glucose moleculesD plasma proteinShow answer & explanation →
Q46.
The respiratory pigment present in human blood is:
A haemoglobinB chlorophyllC haemocyaninD pure myoglobinShow answer & explanation →
Q47.
The volume of air breathed in or out during normal quiet breathing is the:
A tidal volumeB vital capacityC residual volumeD total lung capacityShow answer & explanation →
Q49.
Aerobic respiration is the type of respiration that requires:
A oxygenB only carbon dioxideC nitrogenD direct sunlightShow answer & explanation →
Q50.
The main site of cellular respiration within a cell is the:
A mitochondriaB the nucleusC the ribosomeD the cell wallShow answer & explanation →
Hard - 25 questions Q51.
A pneumotaxic centre in the pons regulates breathing mainly by:
A Increasing the duration of inspirationB Reducing the duration of inspirationC Blocking the medullary rhythm centreD Stimulating surfactant secretionShow answer & explanation →
Q52.
About 97 percent of oxygen is carried by haemoglobin, yet the small dissolved fraction in plasma is physiologically important because it:
A Determines the partial pressure that drives loadingB Neutralises blood pHC Activates carbonic anhydraseD Forms carbamino compoundsShow answer & explanation →
Q53.
In the tissues, the release of oxygen from oxyhaemoglobin is favoured because tissue conditions have:
A High pO<sub>2</sub> and low pCO<sub>2</sub>B Low pO<sub>2</sub> and high pCO<sub>2</sub>C High pO<sub>2</sub> and high pHD Low pCO<sub>2</sub> and high pHShow answer & explanation →
Q54.
The Haldane effect explains why deoxygenated blood carries more CO<sub>2</sub>, because reduced haemoglobin:
A Binds oxygen more stronglyB Blocks carbonic anhydraseC Prevents the chloride shiftD Binds CO<sub>2</sub> and H<sup>+</sup> more readilyShow answer & explanation →
Q55.
The amount of oxygen delivered to tissues by every 100 mL of oxygenated blood under normal conditions is approximately:
A 2 mLB 20 mLC 5 mLD 10 mLShow answer & explanation →
Q56.
Oxyhemoglobin dissociation curve shifts right (Bohr effect) due to:
A Increased blood pH combined with decreased CO<sub>2</sub> stabilizing the relaxed high-affinity state overall in most cases under typical conditionsB Decreased pH, increased CO<sub>2</sub>, increased temperature, increased 2,3-BPG (decreased Hb-O<sub>2</sub> affinity, more O<sub>2</sub> released to tissues)C A fall in core body temperature that slows the hemoglobin conformational transition process according to standard textbooksD Replacement of adult HbA by fetal HbF circulating within the maternal bloodstream during pregnancy in general practice as frequently describedShow answer & explanation →
Q57.
Fetal hemoglobin (HbF) has higher O<sub>2</sub> affinity than adult HbA because:
A It carries two additional heme groups per tetramer for extra oxygen binding capacity in most textbook accountsB Its gamma chains have lower affinity for 2,3-BPG than beta chains of HbA, maintaining higher O<sub>2</sub> saturationC Its heme prosthetic group uses a different iron oxidation state compared to HbA during normal conditionsD It dissolves more readily in fetal plasma due to its smaller overall molecular size as generally observedShow answer & explanation →
Q58.
Respiratory distress syndrome in premature infants is due to:
A Excess surfactant production flooding the alveolar lining with lipid film material in the majority of cases studiedB Insufficient surfactant production (type II alveolar cells immature), causing alveolar collapseC Premature over-development of alveolar septa restricting the gas exchange surface area as widely reportedD Pulmonary edema resulting from cardiac overload unrelated to surfactant levels present in standard practiceShow answer & explanation →
Q59.
Carotid body peripheral chemoreceptors primarily respond to:
A Fluctuations in arterial blood pressure sensed via stretch receptorsB Low arterial PO2 (hypoxia), high PCO2, and low pHC Core body temperature shifts relayed from the hypothalamusD Circulating blood glucose concentration via glucose-sensing neuronsShow answer & explanation →
Q60.
At high altitude, the body's compensatory increase in red blood cell production is triggered mainly by:
A A fall in carbon dioxide levels within the bloodB Hypoxia, which raises erythropoietin secretion from the kidneyC Increased atmospheric pressure acting directly on bone marrowD Faster hemoglobin breakdown occurring in the spleenShow answer & explanation →
Q61.
During strenuous exercise, the rightward shift of the oxygen-hemoglobin dissociation curve aids tissues mainly because it:
A Raises hemoglobin's affinity for carbon monoxide insteadB Lets hemoglobin bind oxygen more tightly in muscle capillariesC Lets hemoglobin release more oxygen at a given partial pressureD Stops further oxygen unloading at the tissue levelShow answer & explanation →
Q62.
Surfactant secreted by alveolar Type II cells is essential because it:
A Lowers surface tension in alveoli, preventing their collapseB Raises surface tension in alveoli to keep them rigid under typical physiological conditionsC Pumps oxygen directly into alveolar capillaries according to standard textsD Converts CO<sub>2</sub> into bicarbonate inside the alveoli in general clinical practiceShow answer & explanation →
Q63.
A decrease in blood pH (acidosis) stimulates an increase in the rate and depth of breathing mainly through:
A Inhibition of the pneumotaxic centre located in the ponsB Reduced oxygen-carrying capacity of plasma proteinsC Chemoreceptors signalling the medullary centre to raise ventilationD Direct contraction of the diaphragm with little nervous inputShow answer & explanation →
Q64.
In a person with emphysema, gas exchange efficiency declines mainly because:
A The diaphragm loses most of its ability to contract in most reference accountsB Damaged alveolar walls merge, cutting the surface area for diffusionC The trachea becomes blocked by excess mucus build-up as frequently documentedD Hemoglobin gradually loses its ability to bind oxygen under normal conditionsShow answer & explanation →
Q65.
Why does carbon monoxide (CO) poisoning severely impair oxygen transport even at low CO concentrations?
A CO reacts with plasma proteins to form toxic precipitates in typical laboratory settingsB CO destroys red blood cells within minutes of exposure as generally observedC CO drives an excessive rise in red blood cell production under usual circumstancesD CO binds hemoglobin far more strongly than oxygen, blocking O<sub>2</sub> sitesShow answer & explanation →
Q66.
The maximum volume of air a person can breathe in and out with effort is the:
A vital capacityB tidal volumeC residual volumeD anatomical dead spaceShow answer & explanation →
Q67.
The respiratory centre that controls the rate of breathing lies in the:
A medulla oblongataB cerebrumC cerebellumD spinal cord aloneShow answer & explanation →
Q68.
Anaerobic respiration in human muscle cells produces:
A lactic acidB ethanolC only carbon dioxideD plain waterShow answer & explanation →
Q69.
Anaerobic respiration in yeast produces ethanol together with:
A carbon dioxideB some lactic acidC pure oxygenD plain waterShow answer & explanation →
Q70.
The exchange of gases between the blood and the body tissues is called ___ respiration:
A internal (tissue)B purely externalC fully anaerobicD only cellularShow answer & explanation →
Q71.
The partial pressure of oxygen is higher in the ___ than in the body tissues:
A alveoliB cellsC musclesD liverShow answer & explanation →
Q72.
The volume of air that remains in the lungs even after the most forceful exhalation is the:
A residual volumeB tidal volumeC vital capacityD inspiratory reserveShow answer & explanation →
Q73.
When haemoglobin combines with oxygen it forms:
A oxyhaemoglobinB carboxyhaemoglobinC methaemoglobinD deoxyhaemoglobinShow answer & explanation →
Q74.
Carbon monoxide is poisonous because it binds to haemoglobin far more strongly than:
A oxygenB nitrogenC waterD glucoseShow answer & explanation →
Q75.
Glycolysis, the first stage of cellular respiration, takes place in the:
A cytoplasmB mitochondriaC nucleusD ribosomeShow answer & explanation →