Breathing and Exchange of Gases - Practice Questions with Answers

Q1.

Gas exchange in the lungs occurs at the:

• A Trachea
• B Bronchi
• C Alveoli
• D Diaphragm

Q2.

Breathing in (inhalation) is caused by the diaphragm:

• A Relaxing and moving up
• B Contracting and moving down
• C Staying still
• D Moving sideways

Q3.

The respiratory pigment found in human red blood cells is:

• A Chlorophyll
• B Hemocyanin
• C Myoglobin
• D Hemoglobin

Q4.

The pleural membrane that directly covers the lung surface is the:

• A Pericardium
• B Parietal pleura
• C Visceral pleura
• D Peritoneum

Q5.

The conducting part of the human respiratory system includes the:

• A Diaphragm, ribs and intercostal muscles under typical physiological conditions
• B Alveoli, alveolar ducts and alveolar sacs in most observed cases
• C Pulmonary artery, vein and capillary bed according to standard texts
• D Nasal passage, pharynx, larynx, trachea and bronchi

Q6.

Most of the carbon dioxide transported in blood is carried as:

• A Bicarbonate ions
• B Carbonic acid crystals
• C Dissolved gas in plasma
• D Carbaminohemoglobin

Q7.

The volume of air that remains in the lungs even after a forceful exhalation is called:

• A Inspiratory reserve volume
• B Tidal volume
• C Residual volume
• D Vital capacity

Q8.

Exhalation (expiration) occurs mainly because the volume of the thoracic cavity:

• A Decreases as the diaphragm and intercostal muscles relax
• B Increases as the diaphragm contracts downward
• C Increases due to outward movement of the rib cage
• D Stays roughly constant while internal pressure rises

Q9.

The exchange of O₂ and CO₂ between alveoli and blood occurs mainly by:

• A Active transport across alveolar walls
• B Facilitated transport using carrier proteins
• C Bulk flow driven by blood pressure
• D Simple diffusion along a pressure gradient

Q10.

The rhythm of breathing in humans is primarily controlled by a centre located in the:

• A Medulla oblongata, in the brainstem
• B Cerebrum, in the frontal region
• C Cerebellum, behind the brainstem
• D Spinal cord, near the cervical region

Q11.

The exchange of gases between an organism and its surroundings is called:

• A respiration
• B digestion
• C circulation
• D excretion

Q12.

In humans, the main organs of breathing are the:

• A lungs
• B kidneys
• C liver lobes
• D heart chambers

Q13.

The gas taken into the body during breathing is:

• A oxygen
• B carbon dioxide
• C nitrogen
• D hydrogen

Q14.

The gas given out of the body during breathing is:

• A carbon dioxide
• B pure oxygen
• C pure nitrogen
• D light helium

Q15.

The windpipe in the respiratory system is also called the:

• A trachea
• B oesophagus
• C larynx
• D pharynx

Q16.

The tiny air sacs of the lungs where gases are exchanged are the:

• A alveoli
• B villi
• C nephrons
• D neurons

Q17.

The muscular sheet below the lungs that aids breathing is the:

• A diaphragm
• B the liver
• C the stomach
• D the heart

Q18.

Taking air into the lungs is called:

• A inhalation
• B exhalation
• C digestion
• D circulation

Q19.

Pushing air out of the lungs is called:

• A exhalation
• B inhalation
• C only respiration
• D filtration

Q20.

The voice box in the respiratory tract is the:

• A larynx
• B trachea
• C alveolus
• D bronchus

Q21.

During the Bohr effect, increased CO₂ in blood:

• A Raises hemoglobin's affinity for O₂ by stabilizing the relaxed conformation
• B Decreases hemoglobin affinity for O₂ (more O₂ released to active tissues)
• C Leaves the oxygen-hemoglobin binding curve completely unshifted
• D Denatures hemoglobin's quaternary structure within red blood cells

Q22.

Tidal volume is:

• A The maximum air volume the lungs can hold after forced inhalation
• B Volume of air inhaled/exhaled in a normal breath (~500 mL)
• C The air remaining in lungs after the most forceful possible exhalation
• D The maximum air that can be exhaled after the deepest possible inhalation

Q23.

Surfactant in alveoli prevents:

• A Gas exchange across the alveolar membrane surface
• B Alveoli collapse by reducing surface tension
• C Infection from inhaled bacteria and airborne pathogens
• D Blood clotting occurring within the lung capillary network

Q24.

Carbon dioxide is transported in blood mainly as:

• A Dissolved CO₂ in plasma, accounting for the majority of transported gas
• B Carbaminohemoglobin formed by binding to globin chains exclusively
• C Bicarbonate ions (HCO₃^-) in plasma (~70%)
• D Carbonic acid accumulating freely in plasma without further dissociation

Q25.

Residual volume refers to the volume of air that:

• A Can be forcibly exhaled after a normal tidal expiration
• B Is inhaled or exhaled during normal quiet breathing
• C Remains in the lungs even after the most forceful expiration
• D Can be additionally inhaled after a normal tidal inspiration

Q26.

Most of the oxygen transported in the blood is carried:

• A Bound to plasma albumin proteins according to standard texts
• B Dissolved directly in blood plasma in most observed cases
• C As bicarbonate ions in plasma under typical physiological conditions
• D Bound to haemoglobin within red blood cells

Q27.

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 alveoli
• B Remain in the alveoli without net movement
• C Diffuse from the alveoli into the blood
• D Bind irreversibly to carbon dioxide in the alveolar air

Q28.

Contraction of the diaphragm during inspiration causes it to:

• A Pull the lungs downward without changing thoracic volume
• B Dome upward, decreasing the volume of the thoracic cavity
• C Remain stationary while the rib cage does all the work
• D Flatten, increasing the volume of the thoracic cavity

Q29.

Hyperventilation can lead to a drop in blood CO₂ levels, which in turn causes:

• A A rise in blood pH, since less carbonic acid is formed
• B Increased binding of CO₂ to haemoglobin as carbaminohaemoglobin
• C No change in pH, since CO₂ does not affect blood acidity
• D A fall in blood pH, due to excess bicarbonate accumulation

Q30.

Which respiratory centre, located in the medulla, primarily sets the basic rhythm of breathing?

• A Medullary rhythm/respiratory centre
• B Carotid body chemoreceptors
• C Aortic body chemoreceptors
• D Pneumotaxic centre in the pons

Q31.

Oxygen is transported in the blood mainly bound to:

• A haemoglobin
• B only the plasma
• C white blood cells
• D the platelets

Q32.

Gas exchange in the lungs takes place by the process of:

• A diffusion
• B active transport
• C filtration
• D osmosis

Q33.

The two tubes that branch from the trachea into the lungs are the:

• A bronchi
• B bronchioles
• C alveoli
• D larynges

Q34.

During inhalation, the diaphragm:

• A contracts and flattens
• B relaxes and domes up
• C disappears entirely
• D stops all movement

Q35.

Most carbon dioxide is carried in the blood in the form of:

• A bicarbonate ions
• B only free gas
• C glucose molecules
• D plasma protein

Q36.

The respiratory pigment present in human blood is:

• A haemoglobin
• B chlorophyll
• C haemocyanin
• D pure myoglobin

Q37.

The volume of air breathed in or out during normal quiet breathing is the:

• A tidal volume
• B vital capacity
• C residual volume
• D total lung capacity

Q38.

Cellular respiration releases usable energy in the form of:

• A ATP
• B DNA
• C glucose
• D RNA

Q39.

Aerobic respiration is the type of respiration that requires:

• A oxygen
• B only carbon dioxide
• C nitrogen
• D direct sunlight

Q40.

The main site of cellular respiration within a cell is the:

• A mitochondria
• B the nucleus
• C the ribosome
• D the cell wall

Q41.

Oxyhemoglobin dissociation curve shifts right (Bohr effect) due to:

• A Increased blood pH combined with decreased CO₂ stabilizing the relaxed high-affinity state overall in most cases under typical conditions
• B Decreased pH, increased CO₂, increased temperature, increased 2,3-BPG (decreased Hb-O₂ affinity, more O₂ released to tissues)
• C A fall in core body temperature that slows the hemoglobin conformational transition process according to standard textbooks
• D Replacement of adult HbA by fetal HbF circulating within the maternal bloodstream during pregnancy in general practice as frequently described

Q42.

Fetal hemoglobin (HbF) has higher O₂ affinity than adult HbA because:

• A It carries two additional heme groups per tetramer for extra oxygen binding capacity in most textbook accounts
• B Its gamma chains have lower affinity for 2,3-BPG than beta chains of HbA, maintaining higher O₂ saturation
• C Its heme prosthetic group uses a different iron oxidation state compared to HbA during normal conditions
• D It dissolves more readily in fetal plasma due to its smaller overall molecular size as generally observed

Q43.

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 studied
• B Insufficient surfactant production (type II alveolar cells immature), causing alveolar collapse
• C Premature over-development of alveolar septa restricting the gas exchange surface area as widely reported
• D Pulmonary edema resulting from cardiac overload unrelated to surfactant levels present in standard practice

Q44.

Carotid body peripheral chemoreceptors primarily respond to:

• A Fluctuations in arterial blood pressure sensed via stretch receptors
• B Low arterial PO2 (hypoxia), high PCO2, and low pH
• C Core body temperature shifts relayed from the hypothalamus
• D Circulating blood glucose concentration via glucose-sensing neurons

Q45.

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 blood
• B Hypoxia, which raises erythropoietin secretion from the kidney
• C Increased atmospheric pressure acting directly on bone marrow
• D Faster hemoglobin breakdown occurring in the spleen

Q46.

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 instead
• B Lets hemoglobin bind oxygen more tightly in muscle capillaries
• C Lets hemoglobin release more oxygen at a given partial pressure
• D Stops further oxygen unloading at the tissue level

Q47.

Surfactant secreted by alveolar Type II cells is essential because it:

• A Lowers surface tension in alveoli, preventing their collapse
• B Raises surface tension in alveoli to keep them rigid under typical physiological conditions
• C Pumps oxygen directly into alveolar capillaries according to standard texts
• D Converts CO₂ into bicarbonate inside the alveoli in general clinical practice

Q48.

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 pons
• B Reduced oxygen-carrying capacity of plasma proteins
• C Chemoreceptors signalling the medullary centre to raise ventilation
• D Direct contraction of the diaphragm with little nervous input

Q49.

In a person with emphysema, gas exchange efficiency declines mainly because:

• A The diaphragm loses most of its ability to contract in most reference accounts
• B Damaged alveolar walls merge, cutting the surface area for diffusion
• C The trachea becomes blocked by excess mucus build-up as frequently documented
• D Hemoglobin gradually loses its ability to bind oxygen under normal conditions

Q50.

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 settings
• B CO destroys red blood cells within minutes of exposure as generally observed
• C CO drives an excessive rise in red blood cell production under usual circumstances
• D CO binds hemoglobin far more strongly than oxygen, blocking O₂ sites

Q51.

The maximum volume of air a person can breathe in and out with effort is the:

• A vital capacity
• B tidal volume
• C residual volume
• D anatomical dead space

Q52.

The respiratory centre that controls the rate of breathing lies in the:

• A medulla oblongata
• B cerebrum
• C cerebellum
• D spinal cord alone

Q53.

Anaerobic respiration in human muscle cells produces:

• A lactic acid
• B ethanol
• C only carbon dioxide
• D plain water

Q54.

Anaerobic respiration in yeast produces ethanol together with:

• A carbon dioxide
• B some lactic acid
• C pure oxygen
• D plain water

Q55.

The exchange of gases between the blood and the body tissues is called ___ respiration:

• A internal (tissue)
• B purely external
• C fully anaerobic
• D only cellular

Q56.

The partial pressure of oxygen is higher in the ___ than in the body tissues:

• A alveoli
• B cells
• C muscles
• D liver

Q57.

The volume of air that remains in the lungs even after the most forceful exhalation is the:

• A residual volume
• B tidal volume
• C vital capacity
• D inspiratory reserve

Q58.

When haemoglobin combines with oxygen it forms:

• A oxyhaemoglobin
• B carboxyhaemoglobin
• C methaemoglobin
• D deoxyhaemoglobin

Q59.

Carbon monoxide is poisonous because it binds to haemoglobin far more strongly than:

• A oxygen
• B nitrogen
• C water
• D glucose

Q60.

Glycolysis, the first stage of cellular respiration, takes place in the:

• A cytoplasm
• B mitochondria
• C nucleus
• D ribosome