Breathing and Exchange of Gases

Air is breathed through

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The pathway of inhaled air is- Nostrils -Pharynx (common passage for food and air) -larynx (voice box)-trachea (the wind pipe)-bronchi (2 for each side lungs)-bronchioles (give arise to alveolar ducts) -alveoli (the exchange site for gases in the form of small sacs or pouches).

What is vital capacity of our lungs?

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Vital capacity of lungs is largest possible expiration after largest possible inspiration that is greatest. Volume of air can be exchanged in single respiration or amount of air breathe in and out with greatest possible effort. VC = TRV + TV + ERV = 3000 + 500 + 1100 = 4600 ml.

Which of the following is the volume of air inspired or expired during a normal respiration?

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The volume of air inspired or expired during a normal respiration is called tidal volume. A healthy man can inspire or expire approximately 6000 to 8000 ml of air per minute.

The exchange of gases in the alveoli of the lungs takes place by

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Gaseous exchange between blood (dissolved phase) and alveolar air (gaseous phase) across respiratory membrane occurs by simple diffusion. Obviously, it depends upon the concentration gradient (= partial pressure) of the concerned gases in blood and alveolar air.

How many molecules of O2 (maximum) can be carried by a single haemoglobin molecule?

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Each haemoglobin molecule can carry a maximum of four molecules of O2.

Which is a common passage for swallowing food while breathing?

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The pharynx provides passage to both air and food .

The alveolar epithelium in the lungs is

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The very thin alveolar wall (about 0.0001mm) is composed of moist, nonciliated, squamous epithelial cells.

Skin is an accessory organ of respiration in

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Frog has lungs as its main respiratory organs but during hibernation & aestivation and during its habitat in water it respires through skin.

What is the process of exchange of gases between blood and body cells called?

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The process of exchange of gases between blood and cells is called internal respiration.

Which of the following is the primary chemical stimulus for breathing?

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The concentration of carbon dioxide in blood is the primary chemical stimulus for breathing.

O2 is transported in vertebrates as

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oxygen combines with hemoglobin to form oxyhemoglobin that is transported in the vertebrates through the blood.

Which of the following cause is the reason for asthma?

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Difficulty in breathing (asthma) is due to inflammation of bronchi and bronchi-oles.

Which of the following helps lungs stay inflated?

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Lungs rely on a vacuum within the chest to stay inflated.

Which one of the following organs in the human body is most affected due to shortage of oxygen?

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Brain is the most vital organ. It stops functioning in the absence of O2.

The carbon dioxide is transported via blood to lungs as

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Carbon dioxide is transported via blood to lungs mostly as carbaminohaemoglobin and carbonic acid. It is released in lungs in exchange with oxygen.

Under which condition more number of CO2 binds to haemoglobin?

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When pCO2 is high and pO2 is low in the tissues more binding of CO2 occurs. When the pCO2 is low and pO2 is high as in the alveoli, dissociation of CO2 from carbamino-haemoglobin takes place.

The breathing controlling center of medulla oblongata is mainly under

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The breathing controlling center of medulla oblongata is mainly under chemical control.

Which of the following is the most important substrate for respiration?

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Oxygen is mainly utilized to break down glucose and to derive energy for various biological activities in the human body.

Intercostal muscles occur in

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Intercostal muscles (external intercostal & internal intercostal) are attached with the ribs which help in the movement of rib cage during breathing.

Which of the following muscles help breathing?

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The intercostal muscles between the ribs help breathing. They help to change the internal air pressure by lifting and relaxing the ribcage along with the diaphragm.

Which of the following part of respiratory organ is called vocal cords?

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Larynx is a cartilaginous box which helps in sound production and hence it is called vocal cards (sound box).

Vital capacity of lungs of an average human is

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Vital capcity is the amount of air one can inhale and exhale after forced expiration and inhalation respectively. It varies from 3000-4500 ml. TLC = VC + RV

Oxygen carrying capacity of blood is

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At 15 gm /100 ml of haemoglobin, the oxygen carrying capacity would be 19.4 ml. Blood leaving tissue carries about 14.4 ml of O2/100 ml.

The structure which prevents the entry of food into respiratory tract is

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During swallowing epiglottis cover the glottis,prevent the entry of food into respiratory tract.

Which of the following factor affects the binding of O2 with the haemoglobin?

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Binding of oxygen with haemoglobin is primarily related to partial pressure of O2. Apart from the factors listed in the options, partial pressure of CO2, hydrogen ion concentration and temperature are the other factors that interfere with the binding of O2 with haemoglobin.

Which of the following helps in studying the effects of factors like partial pressure of O2, partial pressure of CO2, hydrogen ion concentration, and temperature in binding of O2 with haemoglobin?

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When percentage saturation of haemoglobin with O2 is plotted against the pO2, a sigmoid curve is obtained and this curve is called “Oxygen dissociation curve”. This curve is useful in studying the effects of factors like partial pressure of O2, partial pressure of CO2, hydrogen ion concentration, and temperature in binding of O2 with haemoglobin.

Vocal Cards are situated at

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Inside the larynx there are vocal cords. These are two pairs of fold of mucous membrane that extend into the lumen of the larynx from the sides.

Which of the following is not the function of conducting parts of the respiratory system?

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In the given options “Exchange of O2 and CO2 ” is the function of exchange part, not the conducting parts. The rest of the options are the functions of conducting parts.

Mark the correct statement

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Trachea is a membranous tube supported by "C" shaped hyaline cartilage ring. The cartilage ring protects the trachea from collapse and injury.

Which have no specific organ for respiration but respire?

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In earthworm, there is no specific organ for respiration. Heamoglobin is dissolved in the plasma.

Class 11th Biology - 17 Breathing and Exchange of Gases MCQs
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Class 11th Biology - 17 Breathing and Exchange of Gases MCQs