Test: Human Physiology: Respiratory System - 3

30 Questions MCQ Test Zoology for Class 11 - Notes and Tests | Test: Human Physiology: Respiratory System - 3

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The alveolar epithelium in the lung is

[C.B.S.E. 1990, B.H.U. 1996]

Solution: Alveoli has simple squamous epithelium and it does not have cilia.

Carbon dioxide is transported from tissue to respiratory surface by only

[C.B.S.E. 1993]


Blood is the medium of transport for oxygen and carbon dioxide. About 97 per cent of oxygen is transported by RBCs in the blood. The remaining 3 per cent of oxygen is carried in a dissolved state through the plasma. Nearly 20-25 per cent of carbon dioxide is transported by RBCs, whereas 70 per cent of it is carried as bicarbonate ions. About 7 per cent of carbon dioxide is carried in a dissolved state through plasma.


Respiratory centre is situated in

[C.B.S.E. 1999]


Human beings have a significant ability to maintain and moderate the respiratory rhythm to suit the demands of the body tissues. This is done by the neural system. A specialised centre present in the medulla region of the brain called as respiratory rhythm centre, is primarily responsible for this regulation.
So, the correct answer is option B.


Air is breathed through

[Pb. P.M.T 1999, C.B.S.E. 1994]


The respiratory system includes the nose, mouth, throat, voice box, windpipe, and lungs. Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified.


Carbonic anhydrase is mostly active in

[C.E.T. Chd. 2000, Manipal 2001]


RBCs contain a very high concentration of the enzyme, carbonic anhydrase and minute quantities of the same is present in the plasma too. This enzyme facilitates the production of carbonic acid from carbon dioxide and water. It also catalyzes the dissociation of carbonic acid into bicarbonate ions and protons.
Thus, the correct answer is option A.


Common feature of human and insect trachea is

[A.F.M.C. 1994]


The tracheae in insects are supported by strengthening or supporting rings, similar to the tracheae in the human's respiratory system. These strengthening rings are made of chitin, which is the same material as found on the outside the insect.
Therefore, the correct answer is option B.


Presence of large number of alveoli around alveolar ducts opening into bronchioles in mammalian lungs is

[C.B.S.E. 1995]


Alveoli is a characteristic feature of mammalian lungs. The pulmonary alveoli from the terminal ends of the respiratory tree and from these the branches out the alveolar sacs and ducts which act as efficient sites for gaseous exchange.  Besides the epithelial layer and extracellular matrix, these contain collagen and elastic fibres. which stretch as the alveoli are filled with air and spring back to expel carbon dioxide during exhalation. Though, a small amount of air is always present which prevents the lungs from collapsing. 
So, the correct option is 'An efficient system of ventilation with little residual air'.


During transport of CO2, blood does not become acidic due to

[C.B.S.E. 1995]


Human blood contains a buffer of carbonic acid (H2CO3) and bicarbonate anion 
(HCO3-) in order to maintain blood pH between 7.35 and 7.45, as a value higher than 7.8 or lower than 6.8 can lead to death. In this buffer, hydronium and bicarbonate anion are in equilibrium with carbonic acid.


Carbon monoxide has greater affinity for haemoglobin as compared to oxygen

[C.B.S.E. 1995]


Carbon monoxide has 210 times greater affinity for haemoglobin than oxygen. A small environmental concentration will thus cause toxic levels of carboxyhemoglobin. The affinity of carbon monoxide for myoglobin is even greater than for haemoglobin 1. Binding to cardiac myoglobin causes myocardial depression, hypotension and arrhythmias. Cardiac decompensation results in further tissue hypoxia and is ultimately the cause of death. Thus, option B.


At high altitude, RBC of human blood will

[C.B.S.E. 1995, Pb. P.M.T. 1999]


At high altitudes, there is a decrease in oxygen hemoglobin saturation. This hypoxic condition causes hypoxia-inducible factor 1 (HIF- 1) to become stable and stimulates the production of erythropoietin (EPO), a hormone secreted by the kidneys. EPO stimulates red blood cell production from bone marrow in order to increase hemoglobin saturation and oxygen delivery. Thus, the total number of RBC increases.


CO2 is transported as

[C.B.S.E. 1995]

Solution: The carbon dioxide is transported dissolved in the plasma. Some carbon dioxide is transported as carbaminohemoglobin. However, most carbon dioxide is transported as bicarbonate. As blood flows through the tissues, carbon dioxide diffuses into red blood cells, where it is converted into bicarbonate.

About 1500 ml of air left in lungs is called

[C.B.S.E. 1996]

Solution: Tidal volume + residual volume is the air left in lungs (500ml) (1000ml) after normal respiration but none of the option matches so tidal volume is more appropriate as residual volume will always remain in lungs till death.The question is asking about the present increase in volume of lungs in due to tidal volume as per me

Which one protects the lungs

[B.H.U. 1996]

Solution: Locate Those Lungs
Instead, the lung on the left side of your body is a bit smaller than the lung on the right. This extra space on the left leaves room for your heart. Your lungs are protected by your rib cage, which is made up of 12 sets of ribs.

 Which one has the lowest value

[B.H.U. 1996]


During normal breathing , the volume of air inspired or expired is known as tidal volume. It's value is approximately 500ml which is very low as compared to vital capacity (3400ml- 4800ml), inspiratory reserve volume (2500ml-3000ml) and expiratory reserve volume (1000ml-1100ml).
So, the tidal volume has the lowest value.


Amount of oxygen present in one gram of haemoglobin is

[A.I.I.M.S.1997, Har, PMT 2000]

Solution: B is right answer we have to remember 1 gm Hb contains 3.4 mg iron and 1.34ml O2.

Compound soluble in water which does not impede oxygen transportation is

[A.I.I.M.S. 1997]


SO2 is a soluble compound that dissolves in water but not in blood and so it does not impede oxygen transport. CO and NO both compete with oxygen for binding with haemoglobin.


In lungs air is separated from venous blood by

[C.B.S.E. 1997]


Alveoli are the primary sites of exchange of gases. Exchange of gases also occurs between blood and tissues. Oxygen and carbon dioxide are exchanged at these sites by simple diffusion mainly based on pressure/ concentration gradient. Solubility of the gases as well as the thickness of the membranes involved in diffusion are some important factors that can affect the rate of diffusion. The diffusion membrane is made up of three major layers namely, the thin squamous epithelium of alveoli, the endothelium of the alveolar capillaries. However, its total thickness is much less than a millimetre.
Therefore, the correct answer is option B.


 In carbon monoxide poisoning there is

[A.F.M.C. 1997]


In carbon monoxide poisoning there is decrease in free haemoglobin. 


Exchange of gases in lung alveoli occurs through

[C.B.S.E. 1998]


External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. ... The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes.


Haemoglobin is

[C.B.S.E. 1999]


Haemoglobin, is the iron-containing oxygen-transport metalloprotein in the red blood cells of almost all vertebrates as well as the tissues of some invertebrates. Hemoglobin in blood carries oxygen from the lungs or gills to the rest of the body. it's a respiratory pigment.


Vocal cords occur in

[M.P. P.M.T. 1999]

Solution: The vocal folds, also known as vocal cords.  vocal cords are located within the larynx at the top of the trachea. They are attached posteriorly to the arytenoid cartilages, and anteriorly to the thyroid cartilage. They are part of the glottis which includes the rima glottidis. Function of vocal cords are :-protect the airway from choking on material in the throat. To regulate the flow of air into our lungs. The production of sounds used for speech.

Concentration of carbonic acid does not increase in blood due to presence of

[B.H.U. 1999]


Concentration of carbonic acid does not increase in blood due to presence of Na+. The bicarbonate buffering system of blood is an important buffer system in the acid-base homeostasis of living things, including humans. In plasma, by phosphate buffers, the alkaline phosphates combines with carbonic acid (H2CO3) and forms sodium bi carbonate.

Na2HPO4 + H2CO3 ⇄ NaH2PO4 + NaHCO3


Match the columns

[Karnataka 1999]


Larynx is the other name of voice box.
Epiglottis is the lid of larynx
Trachea is known as wind pipe.
Alveoli are air sacs where gas exchange takes place.


The layer of blood vessel having smooth circular muscles is

[B.H.U. 2000]

Solution: The thick outermost layer of a vessel (tunica adventitia or tunica externa ) is made of connective tissue. The middle layer ( tunica media ) is thicker and contains more contractile tissue in arteries than in veins. It consists of circularly arranged elastic fibers, connective tissue, and smooth muscle cells.

Oxygen carried by blood is liberated in

[C.E.T. Chd. 2000]

Solution: Option B is the best becz option a and d can be eliminted easily then option c can also be eliminted as at lungs co2 liberate.

 Adam's Apple represents

[Pb. P.M.T. 2000]


The Adam's apple is also called as the laryngeal prominence. It is a feature of the human neck and is referred to the lump or protrusion that is formed by the angle of the thyroid cartilage surrounding the larynx. It consists of three hyaline cartilages as the thyroid cartilage, the cricoid cartilage, and the arytenoid cartilage.
Thus, the correct answer is the option C.


Hiccough (hiccup) is due to activity of

[Manipal 2001]


Hiccup is also called as a hiccough. It is an involuntary activity of the diaphragm. During hiccups, the diaphragm muscle shows several involuntary contractions.When the diaphragm muscle contracts, the opening between the vocal cords snaps shut to check the inflow of air.This results in the hic or hiccup sound. This results due to irritation of the nerves.


Respiratory centre of brain is stimulated by

[A.I.I.M.S 2000]


Respiratory centre of brain is stimulated by increased conc. of CO2 in blood , and to lesser extent by decreased conc. of O2. This stimulation causes an increase in the rate & depth of breathing , thus blowing off excess CO2 and reducing blood acidity.


Carbon dioxide entering erythrocytes reacts with water to form carbonic acid. The enzyme is

[H.P.P.M.T. 2001]


RBCs contain a very high concentration of the enzyme, carbonic anhydrase and minute quantities of the same is present in the plasma too. This enzyme facilitates the reaction between carbon dioxide and water to form carbonic acid and its dissociation into bicarbonate ions and protons.


Determination of oxygen carried by haemoglobin is done by

[C.E.T. Chd. 2001]

Solution: Option B Binding Of Hb with O2 mainly depends on Partial pressure of oxygen P(O2).. but there are also other factors[ph,temp,P(CO2)] which can interfere.Thats why at high altitude due to less P(O2)binding of haemoglobin decreases so to compensate that body produces more RBC.
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