183 Breathing and Exchange of Gases 1. Skin is an accessory organ of respiration in (a) humans (b) frog (c) rabbit (d) lizard Frog has lungs as its main respiratory organs but during hibernation & aestivation and during its habitat in water it respires through skin. 2. The alveolar epithelium in the lungs is [1990] (a) nonciliated columnar (b) nonciliated squamous (c) ciliated columnar (d) ciliated squamous The very thin alveolar wall (about 0.0001 mm) is composed of moist, nonciliated, squamous epithelial cells. 3. Carbon dioxide is transported from tissues to respiratory surface by only [1993] (a) plasma and erythrocytes (b) plasma (c) erythrocytes (d) erythrocytes and leucocytes CO 2 from the respiratory tissues to the lungs is transported by the blood in 3 ways: (i) In dissolved state or as a physical solution: Very small amount physically dissolved in plasma (7% i.e. 0.3 ml of CO 2 by each 100 ml of blood) (ii) Bicarbonate ions: 70% (i.e. 2.5 ml per 100 ml of blood) CO 2 diffuses in plasma & then into RBCs where it (in the presence of carbonic anhydrase) combines with H 2 O to form carbonic acid which is almost spontaneously dissociated into hydrogen ion & bicarbonate ions. (iii) Carbaminohaemoglobin: 23% (i.e. 1 ml of CO 2 per 100 ml of blood) combines with haemoglobin forming an unstable compound. 4. Oxygen dissociation curve of haemoglobin is [1994] (a) Sigmoid (b) Hyperbolic (c) Linear (d) Hypobolic It is the relationship between the percentage saturation of haemoglobin (by volume) in the blood and the oxygen tension (in partial tension) PO 2 of the blood. It is usually a sigmoid plot. Haemoglobin molecules can bind up to four oxygen molecules in a reversible way. The shape of the curve results from the interaction of bound oxygen molecules with incoming molecules. The binding of the first molecule is difficult. However, this facilitates the binding of the second and third molecules, and it is only when the fourth molecule is to be bound that the difficulty increases, partly as a result of crowding of the haemoglobin molecule, partly as a natural tendency of oxygen to dissociate. (Bohr effect: CO p H, temp.) 2 ph DPG Temp ph DPG Temp (Haldane effect: O displaces CO for Hb) 2 2 The O 2 -Hb dissociation curve is a sigmoidal curve that represents the relationship between O 2 concentration and the percentage saturation of Hb. As the concentration increases from about 90% there is a significant plateau in the curve, which has several important biological repercussions. 5. Air is breathed through [1994] (a) Trachea lungs larynx pharynx alveoli (b) Nose larynx pharynx bronchus alveoli bronchioles (c) Nostrils pharynx larynx trachea bronchi bronchioles alveoli (d) Nose mouth lungs The pathway of inhaled air is - Nostrils - pharynx (common passage for food & 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).
184 6. Although much CO 2 is carried in blood, yet blood does not become acidic, because [1995] (a) it is absorbed by the leucocytes (b) blood buffers play an important role in CO 2 transport. (c) it combines with water to form which is neutralized by NaCO 3 (d) it is continuously diffused through tissues and is not allowed to accumulate CO 2 enters RBC and reacts with water to form carbonic acid. Carbonic acid dissociates to form bicarbonate and hydrogen ions. Some bicarbonate ions are transported in erythrocytes while some diffuse into the blood plasma. Exit of bicarbonate ions change the ionic balance between the plasma and erythrocytes. To restore this balance chloride ions diffuse from plasma into erythrocytes. Due to this the ph of blood is maintained. 7. The carbon dioxide is transported via blood to lungs as [1995] (a) dissolved in blood plasma (b) in the form of carbonic acid only (c) in combination with haemoglobin only (d) carbaminohaemoglobin and as carbonic acid Carbon dioxide is transported via blood to lungs mostly as carbaminohaemoglobin and carbonic acid. It is released in lungs in exchange with oxygen. 8. People living at sea level have around 5 million RBC per cubic millimeter of their blood whereas those living at an altitude of 5400 metres have around 8 million. This is because at high altitude [1995, 2006] (a) atmospheric O 2 level is less and hence more RBCs are needed to absorb the required amount of O 2 to survive (b) there is more UV radiation which enhances RBC production (c) people eat more nutritive food, therefore more RBCs are formed (d) people get pollution - free air to breathe and more oxygen is available At the altitude of 5400 meters the low atmospheric pressure of O 2 will be too low so the solubility of oxygen in the blood will be very less hence the oxygen carried by each RBC will be too less. But to fulfill the oxygen requirement of the body blood has to carry more oxygen to the body tissue and this is done by the increased no. of RBCs. 9. The quantity 1500 ml in the respiratory volumes of a normal human adult refers to [1996] (a) maximum air that can be breathed in and breathed out (b) residual volume (c) expiratory reserve volume (d) total lung capacity The total volume of air that can be expelled from the lungs after maximum inspiration and then expiring to the maximum is known as the vital capacity. The volume of air that remains inside lungs at the end of maximum forceful expiration is the residual volume. Expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after a normal tidal expiration. Total lung capacity is the maximum volume of air that can be contained in the lungs after maximum inspiration. 10. In alveoli of the lungs, the air at the site of gas exchange, is separated from the blood by (a) alveolar epithelium only (b) alveolar epithelium and capillary endothelium (c) alveolar epithelium, capillary endothelium and tunica adventitia (d) alveolar epithelium, capillary endothelium, a thin layer of tunica media and tunica adventitia Alveoli are the site of the respiratory exchange of gases. Oxygen from the alveolar air diffuses through the alveolar epithelium and the capillary endothelium
185 into the capillary blood and carbon dioxide diffuses in the opposite direction. 11. The exchange of gases in the alveoli of the lungs takes place by [1998] (a) simple diffusion (b) osmosis (c) active transport (d) passive transport 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. 12. The process of migration of chloride ions from plasma to RBC and of carbonate ions from RBC to plasma is [1999] (a) chloride shift (b) ionic shift (c) atomic shift (d) Na+ pump During the transport of CO 2 through the blood, bicarbonate ions diffuse out of RBCs while chloride ions from plasma enter the RBCs to maintain ionic equilibrium. This is called chloride shift. 13. Which one of the following organs in the human body is most affected due to shortage of oxygen? [1999] (a) intestine (b) skin (c) kidney (d) brain Brain is the most vital organ. It stops functioning in the absence of O 2. 14. When CO 2 concentration in blood increases, breathing becomes [2004] (a) shallower and slow (b) there is no effect on breathing (c) slow and deep (d) faster and deeper The breathing becomes faster and deeper in order to oxygenate the blood at a fast rate. Shallow and slow breathing occurs during rest. 15. Blood analysis of a patient reveals an unusually high quantity of carboxyhaemoglobin content. Which of the following conclusions is most likely to be correct? The patient has been inhaling polluted air containing unusually high content of [2004] (a) carbon disulphide (b) chloroform (c) carbon dioxide (d) carbon monoxide Carboxyhaemoglobin is the stable product formed by the association of CO and Hb in the blood. The association of carbon dioxide and haemoglobin forms carbamino haemoglobin. 16. Which one of the following mammalian cells is not capable of metabolising glucose to carbon-dioxide aerobically? [2007] (a) unstraited muscle cells (b) liver cells (c) red blood cells (d) white blood Since RBCS do not have mitochondria so they can respire only anaerobically. 17. Intercostal muscles occur in [1988] (a) abdomen (b) thigh (c) ribs (d) diaphragm Intercostal muscles (External intercostal & Internal intercostal) are attached with the ribs which help in the movement of rib cage during breathing. 18. What is vital capacity of our lungs? (a) Inspiratory reserve volume plus tidal volume (b) Total lung capacity minus expiratory reserve volume (c) Inspiratory reserve volume plus expiratory reserve volume (d) Total lung capacity minus residual volume
186 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 breath in and out with greatest possible efforts. VC = TRV +TV + ERV = 3000 + 500 + 1100 = 4600 ml. 19. Listed below are four respiratory capacities (i iv) and four jumbled respiratory volumes of a normal human adult: Respiratory Respiratory capacities volumes (i) Residual volume 2500mL (ii) Vital capacity 3500mL (iii) Inspiratory reserve 1200mL volume (iv) Inspiratory capacity 4500mL Which one of the following is the correct matching of two capacities and volumes? [2010] (a) (ii) 2500mL, (iii) 4500mL (b) (iii) 1200mL, (iv) 2500mL (c) (iv) 3500 ml, (i) 1200mL (d) (i) 4500 ml, (ii) 3500mL 20. Which two of the following changes (a d) usually tend to occur in the plain dwellers when they move to high altitudes (3,500 m or more)? (i) Increase in red blood cell size (ii) Increase in red blood cell production (iii) Increased breathing rate (iv) Increase in thrombocyte count Changes occurring are: [2010] (a) (ii) and (iii) (b) (iii) and (iv) (c) (i) and (iv) (d) (i) and (ii) At high altitude, the body undergoes numerous changes in order to increase oxygen delivery to cells and improve the efficiency of oxygen usage. The early changes include increased breathing rate and increased red blood cell production. 21. Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort? [2011M] (a) One can breathe out air totally without oxygen. (b) One can breathe out air through eustachian tubes by closing both the nose and the mouth. (c) One can consiously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all. (d) The lungs can be made fully empty by forcefully breathing out all air from them Eustachian tube connect middle ear cavity (Tympanic cavity) with nasopharynx, approximately it is 35 mm long in adults, which helps in breathing out by closing both the nose and mouth. 22. Which of the following are the correct statement for respiration in human [2012] (a) Cigarette smoking may lead of inflammation of bronchi (b) Neural signals from pneumotaxic centre in pons region of brain can increase the duration of inspiration (c) Workers in grinding and stone - breaking industries may suffer from lung fibrosis (d) About 90% of carbon dioxide (CO 2 ) is carried by haemoglobin as carbamino haemoglobin. (a) and (c). Neural signals from pneumotaxic center in pons region of brain can limit the duration of inspiration. About 25% of carbodioxide (CO 2 ) is carried by haemoglobin as carboxyhaemglobin. 23. Breakdown product of haemoglobin is [1988] (a) Bilirubin (b) Iron (c) Biliverdin (d) Calcium In this type of question one must answer reasonably as the breakdown products of haemoglobin are haem i.e. Iron & Globin protein which is then converted into
187 yellowish substance bilirubin which is extracted by the liver cells from the blood & stored in the form of bile in gall bladder. The more appropriate answer is Iron as we have to mark only one option. If one had liberty to mark both the options then he/she would have marked both bilirubin and Iron. 24. Child death may occur in the marriage between (a) Rh+ man and Rh+ woman (b) Rh+ man and Rh woman (c) Rh man and Rh woman (d) Rh man and Rh+ woman Rh factor was discovered by Karl Landsteiner. A child of Rh+ man will be Rh+ whether the mother is Rh+ or Rh. If the mother is Rh+ then there will be no problem but if mother is Rh so when the blood of Rh+ child (in womb) mixes with the blood of Rh mother then some antibodies in mother s blood are formed against Rh+ factor which coagulate the womb blood causing death. If birth takes place then there is a possibility of child death in early years. This in known as erythroblastosis foetalis. In most cases the Ist pregnancy may succeed but after that it fails. 25. Which one of the following is one of the paths followed by air/o2 during respiration in an adult male Periplaneta americana as it enters the animal body? [NEET Kar. 2013] (a) Hypopharynx, mouth, pharynx, trachea, tissues (b) Spiracle in metathorax, trachea, tracheoles, oxygen diffuses into cells (c) Mouth, bronchial tube, trachea, oxygen enters cells (d) Spiracles in prothorax, tracheoles, trachea, oxygen diffuses into cells The number of spiracles in cockroach is 10-pairs (2-pairs in thoracic and 8-pairs in abdominal region). The thoracic pairs of spiracles are present on pleuron between prothorax - mesothorax and metathorax. Each spiracle opens into a chamber called atrium. After atrium the tracheal tube ramifies into fine branches of tracheae, and then tracheoles. : 18