Biology Chapter 17 Breathing And Exchange Of Gases

About 7% of CO₂ is carried in the dissolved state through plasma 

Rate of respiration : The rate of respiration is slightly quicker in women than in men. In normal breathing, expiration succeeds inspiration and is followed by a slight pause of Inspiration-expiration-pause. In sick babies, this order is sometimes reversed and the sequence

becomes : inspiration-pause-expiration. This is described as inverse breathing.

Normal rate per minute

In newly born → 40

At twelve months → 30

From two to five years → 24

In adults → 10-20

Oxygen dissociation curve is the sigmoid curve obtained when the percentage saturation of haemoglobin with O₂ is plotted against the partial pressure of oxygen pO_2.  It helps in the study of the effect of factors like pCO₂, H⁺ concentration etc. on binding of oxygen with haemoglobin. 

The binding of oxygen to haemoglobin is in such a way that the binding of the first oxygen oxygen molecule binds to the haemoglobin, it increases the affinity for the second molecule of oxygen to bind. Subsequently, haemoglobin attracts more oxygen and this gives the curve a sigmoid shape. 

Respiration : Respiration is a catabolic. oxidising and energy liberating process. During this process, exchange of gases takes place, i.e. oxygen is taken into tissue cells and carbon dioxide produced as metabolic waste matter is given out. The energy released by oxidation of food substances such as carbohydrates, fats and proteins is stored in the form of ATP molecules. 

Respiration serves the following purposes :

(1) It helps in keeping the functions of blood normal by adjusting changes in the pH of blood.

(2) It helps in maintaining proper oxygen concentration in the body.

(3) It helps in maintaining normal body temperature.

(4) It provides energy for the activities of the body. 

Respiratory quotient (R.Q.) : It is the ratio of the volume of carbon dioxide produced to the volume of oxygen used in a unit time.

It is different for different foods. For glucose, it is

For Fats it is about 0.7 and For proteins it is about 0.85. 

There are two types of respiration :

1. Direct respiration : In this type the atmospheric oxygen directly reaches all the cells of the body .e.g., protozoans, flat worms, coelentrates, insects etc.

2. Indirect respiration : It is the respiration in which oxygen first combines with blood in respiratory organs and then blood transports the oxygen to all the cells of the body e.g. earthworm, frog, human being etc.

 pO2 is higher in the tissue capillaries than in the blood. Since the gases diffuse fro the region having higher partial pressure to the region having low partial pressure. Thus, oxygen leaves the blood from tissue capillaries, but carbon dioxide enters the blood in tissue tissue capillaries.

Respiratory pigments of human being is haemoglobin :

Haemoglobin : It is a red coloured pigment formed of iron and protein. Haemoglobin is a red coloured iron containing pigment present in the RBCs. O₂  binds with haemoglobin in a reversible manner to and form oxyhaemoglobin. One haemoglobin molecule can carry a maximum of four molecules of O₂. 

The respiration is regulated in the following ways :
The neural system is involved in regulating the respiration. 
i. Respiratory rhythm centre - A specialised centre present in the medulla region of the brain is primarily responsible for the regulation of respiration.

ii. Pneumotaxic centre - in the pons region of the brain moderates the functions of the respiratory rhythm centre. Neural signal from this centre can reduce the duration of inspiration and thereby alter the respiratory rate.

iii. A chemosensitive area situated adjacent to the rhythm centre which is highly sensitive to CO2 and hydrogen ions. Increase in these substances can activate the centre which signals the rhythm centre to make the necessary adjustments in the respiratory process by which these substances can be eliminated.

iv. Aortic arch and carotid artery receptore also recognise changes in CO2 and H+ concentration and send necessary signals to the rhythm centre for necessary actions. Oxygen plays a vital role in the regulation of respiratory rhythm.

Animals obtain oxygen in the following five ways :

1. From water or air through moist body surface directly into the body as in Amoeba.

2. From air or water through the thin body wall in blood vessels e.g. Earthworm.

3. From air through spiracles to a system of air tubes-tracheae to tissues and tissue cells or from water through tracheal gills e.g. insects.

4. From water through gill surface to blood vessels and then to tissue cell e.g. fishes and amphibians.

5. From air through moist lung surfaces to blood vessels and from there to tissue cells e.g. animals.

Causes : It may be caused by :

1. Penetrating injury, e.g. compound fracture of rib. 

2. Rupture of the lung over a diseased area, e.g. emphysema.

3. Therapeutic introduction of air to rest the lung.

Haemothorax : It is the presence of blood in the pleural cavity.

It may be caused by :

1. Penetrating chest injury involving blood vessels.

Pleural effusion (excess fluid in the pleural cavity) : It may be caused by :

1. Inflammation, usually due to infection.

2. Malignant tumour involving the pleura.

Conditions necessary for skin to act as respiratory organ are:

1. Skin must be smooth and without exoskeleton.

2. Skin must have lining of mucous cells to keep it moist.

3. Skin must be thin.

4. Skin must have a rich supply of blood.

The rate of diffusion depends on the following factors:

i. Partial pressure gradients of O₂ (pO₂) and CO₂ (pCO₂),
ii. Solubility of the gases.
iii. Thickness of the diffusion surface.

i. Hypoxia is the condition produced due to the lack of oxygen.

ii. Pneumonia :is th inflammation of lungs caused by bacteria Diplococcus pneumoniae,  in which the air sacs fill with pus and may become solid

iii. Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. In this disease, walls present in between the alveoli break, as a result gas exchange area of the lungs is reduced. It may be caused due to oedema, inflammation or mucus deposition in the bronchi.

iv. Cough : It is the expelling of air from the lungs with a sudden sharp sound.

Respiratory tract of man consists of :

1. External nostrils : The external nares are two slits at the lower end of the nose. These open into the nasal chambers.

2. Nasal chambers : Two nasal chambers are separated from each other by nasal septum. Each chamber has the following three regions :

3. Internal nares (conchae) : The nasal chambers open into the nasopharynx by internal nares.

Fig. Respiratory Organs of man

4. Pharynx : Its upper part is called nasopharynx. The internal nares open into it. Its middle part is called oropharynx and lower part is called laryngopharynx.

5. Larynx : The larynx is called the Adam’s apple and is more prominent in men than in women. 

6. Trachea : It is a long thin-walled tube. It extends downward through the neck. In the middle of thorax, it divides into two primary bronchi, one major bronchus enters the right lung and subdivides to form secondary and tertiary bronchi which divide into smaller bronchioles which further divide into alveolar ducts. The latter enter the infundibulum which is made up of central duct and alveoli. All infundibula which get alveolar ducts from one bronchiole is called lobule. The cartilagenous rings are incomplete behind, support the wall of the trachea and bronchi and finally disappear over the bronchioles.

(a) Far more oxygen is released from oxyhaemoglobin in a more active tissue than in a less active one.- This is because in more active tissue PO₂ is lower and PCO₂ is higher. The PO₂ is much lower and the PCO₂ is much higher in an active tissue than less active. Both these favour dissociation of oxyhaemoglobin to deoxyhaemoglobin and molecular oxygen.

(b) Oxygenation of blood promotes the release of carbondioxide from blood in the lungs -  because oxyhaemoglobin is a stronger acid than deoxyhaemoglobin. So, it denotes H⁺ ion which combine into water and CO₂ by carbonic anhydrase. Bicarbonates release CO₂. Affinity of haemoglobin for oxygen is enhanced due to the release of CO₂ from blood in lungs which causes fall in PCO₂ of blood.

Functions of respiratory tract :

1. The cartilages in the trachea keep the respiratory tract extended, allowing for the unobstructed passage of air between the outside atmosphere and the alveoli of the lungs.

2. The mucus lining keeps the respiratory passage moistened and traps particles as dust in the air preventing them from reaching the alveoli.

3. The diameter of the respiratory passages may be altered by muscles in their walls, thus regulating the volume of air entering the lungs.

4. Cells in connective tissue protect against infection and inhaled foreign particles not trapped by mucus. Lymphocytes and plasma cells produce antibodies in the presence of antigens, and macrophages and polymorphonuclear leukocytes are phagocytic. 

5. The respiratory tracts maintains the temperature of the air. 

Pleura : Pleura is the double membrane structure that surrounds the lungs. The space inbetween the two membranes is filled with pleural fluid. 
The outer pleural membrane is in close contact with the thoracic lining whereas the inner pleural membrane is in contact with the lung surface. 
The pleural membrane protects the lungs and the pleural fluid reduces friction on the lung-surface.

Pharyngitis : It is an inflammation of pharynx often called sore throat. It may accompany the common cold and it usually involves the tonsils (tonsilitis).

Laryngitis : It is an inflammation of larynx that often accompanies pharyngitis. In laryngitis inflammation of larynx disturbs the vibration of vocal cords and the person has difficulty in speaking.
Bronchitis : It is an inflammation of the bronchi. The lining of bronchi swells and produces excess mucus.

Asthma : It is more correctly called bronchial asthma. It is  caused due to an allergic reaction to foreign substances that affect the respiratory tract. Allergens stimulate the release of histamine from the mast cells. Histamine has several effects, one of which is to cause bronchial smooth muscle to contract. 

Partial pressure : It is the pressure exerted by individual gas in a mixture of gases.

Air is a mixture of gases like O₂, CO₂, N₂ etc. The partial pressure exerted by O₂ is designated as pO₂. It is called partial pressure of O₂. Similarly partial pressure of CO₂ is written as pCO₂.

Due to pressure gradient  and difference in the partial pressure the gase move from the region of their higher partial pressure to the region of their lower partial pressure.
Thus, O₂ from alveolar air (High pO₂) diffuses into blood (having low pO₂₎ till pO_2. 
CO₂ from blood (High pCO₂₎ diffuses into alveoli ( having low pCO₂₎ . Thus, partial pressure helps in gaseous exchange.

Haemoglobin is a red coloured iron containing pigment present in the RBCs. O₂ binds with haemoglobin in a reversible manner and forms oxyhaemoglobin.
Each haemoglobin molecule can carry a maximum of four molecules of O₂. Binding of oxygen with haemoglobin is primarily related to partial pressure of O₂. 

The high pO2, low pCO2, lesser H⁺ concentration and lower temperature in the alveoli are favourable for the formation of
oxyhaemoglobin, whereas in the tissues,
low pO2, high pCO2, high H⁺ concentration and higher temperature exist which favours dissociation of the oxygen from the haemoglobin. Thus, O₂ gets bound to haemoglobin in the lung surface and gets dissociated at the tissues. 

Any surface that promotes the diffusion of gases must have following four basic features :

1. The surface area must have a relatively large surface area. Diffusion is a slow process, and the larger the area, the more is diffusion. Large surface area is maintained by extensive tissue projections and foldings.

2. The surface must be moist at all times, because oxygen and CO₂ must be dissolved in water to diffuse across cell membranes. Aquatic organisms easily meet this requirement, but it is difficult for the organisms living on land to maintain a moist surface. Many adaptations in terrestrial organisms minimize but can never totally prevent water loss during respiration.

3. A surface for gas exchange must be close to the active cells of the body or to the fluid that transports gases between these cells and the surface. Diffusion is slow to carry gases very deeply into the body of an organism.

4. The membrane should be thin and permeable to the gases

During respiration food is oxidized and CO₂ , H₂O and energy are produced. The energy produced is stored in ATP molecules in mitochondria. Whenever energy is required it is released by ATP molecules.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 684 K Cal

Different types of pulmonary volumes.

1. Tidal volume : It is the air normally inspired or expired. It is approx 500 ml.

2. Inspired reserve volume : It is the additional volume of air inspired with maximum possible effort after normal inspiration. It is approximately 2500 ml.

3. Inspiratory capacity (I.C.) : It is the total amount of air a person can inspire after a normal expiration.  It is the sum of tidal volume and inspiratory reserve volume. 

4. Expired reserve volume (ERV) : It is the amount of air expired with maximum possible effort after normal expiration. It is 1100 ml.

5. Vital capacity : It is the maximumvolume of air a person can breathe in after forced expiration or the maximum amount of air a person can breathe out after forced inspiration. It is the sum total of tidal volume, inspired reserve volume and expired reserve volume.

6. Residual volume (RV): It is the amount of  air left in the lungs after forcible expiration. It is 1100–1200 ml.

7. Functional residual volume : It is the amount of air left in lungs after normal expiration. FRV = ERV +RV.

8. Total lung capacity : It is the amount of air in lungs and respiratory tract after maximum inhalation effort. It is equal to the sum of vital capacity and the residual volume.

Total lung capacity = Vital capacity + Residual volume

9. Dead space : It is the space which contains a part of inspired air during inspiration and a part of expired air during expiration. 

Exchange of gases : The gases are exchanged in alveoli of lungs and cells of the body. The exchange of gases in alveoli occurs between blood and alveolar air.
The alveolar air has pO₂ 104 mm and pO₂ of blood is 40 mm of Hg. Thus, oxygen from alveolar air diffuses into blood till pO₂ of the blood becomes 95 mm.

The pCO₂ of alveolar air is 40 mm and of blood is 45 mm. Thus, CO₂ from blood diffuses into alveolar air. 

Exchange of gases in cells : The blood which is in contact with cells have pO₂ 95 mm and pCO₂ 40 mm while cells of the tissues have pO₂ 40 mm and pCO₂ 45 mm. Thus, oxygen from blood diffuses into the cells and CO₂ from cells diffuses into blood till PCO₂ becomes 46 mm of Hg and PO₂ becomes 40 mm. Now the blood is carried by veins to heart, then to lungs by pulmonary arch. In lungs it is purified.

Diagrammatic representation of exchanges of gases at the alveolus and the body tissues with blood and transport of oxygen and carbon dioxide

The role of the diaphragm and inter costal muscles in breathing :

Mechanism of inspiration : Inspiration or inhaling is taking in of fresh air into lungs. It occurs in following steps :

1. The external intercostal muscles or inspiratory muscles contract and pull the ribs forward and upward thus increasing the volume of thoracic cavity.

2. The radial muscles of diaphragm contract. The diaphragm becomes flat. It also increases volume of thoracic cavity.

3. The abdominal muscles relax. Thus, the organs present in abdominal cavity get compressed to accommodate the flat diaphragm.

All this reduces the pressure of thoracic cavity, the lungs being closely applied to thoracic cavity expand. Thus, pressure of lungs is reduced as compared to the atmospheric pressure. The atmospheric air rushes into lungs via respiratory tract to make the pressure equal. Thus, air is inspired. 

Mechanism of expiration : Expiration is the exhaling of  air. It involves the following steps :

1. The peripheral muscles of the diaphragm relax and push the diaphragm upwards making it convex.

2. Intercostal muscles relax. This reduces the area of the thoracic cavity.

3. Abdominal muscles contract and decrease the thoracic cavity further.

Decrease in thoracic cavity reduces the volume of the lungs. The pressure is increased and the air is expired. 

Transportation of oxygen : It ctake splace in the following way :

1. In solution form : Oxygen is less dissolved in plasma–about 3% gets transported in solution form.

2. As oxyhaemoglobin : Oxygen combines with haemoglobin to form oxyhaemoglobin. One molecule of haemoglobin combines with four molecules of oxygen to form oxyhaemoglobin. In the alveoli there is high pO2, low pCO2, lesser H⁺ concentration and lower temperature, these factors favour the  formation of oxyhaemoglobin. Whereas in the tissues, where low pO2, high pCO2, high H⁺ concentration and higher temperature exist, . Since the Haemoglobin molecules take oxygen from respiratory organs and give oxygen to the cells of the body.

Fig. Diagram of the exchange of gases

About 97% oxygen is carried in combination with haemoglobin.

Transportation of carbon dioxide : It is transported in three forms :

1. In solution form : About 7% CO₂ dissolves in plasma and is transported as such.

2. As bicarbonate : About 70% CO₂ from plasma enters into R.B.C. It combines with water to form carbonic acid in the presence of enzyme carbonic anhydrase. Carbonic acid (H₂ CO₃) splits into H⁺ and HCO^-₃

From erythrocytes bicarbonate ions pass into plasma due to which ionic balance between ions in the plasma and erythrocytes is disturbed. To maintain the balance, the chloride ions diffuse into RBC from plasma. This movement of chloride ions is called chloride shift or Hamburger shift. The latter maintains an acid base equilibrium at pH 7.4 for blood and electrical balance between plasma and RBC.

Most of the bicarbonate is carried by plasma and some of it by RBC.

3. As carbamino-haemoglobin : About 23% CO₂ combines with haemoglobin of RBC to form carbamino-haemoglobin. It combines with amino group. The amount of CO₂ which can be carried by haemoglobin is affected by oxygen tension (Haldane effect). The impure blood is carried to heart and then to lungs. In lungs 100 ml of blood releases 3.7 ml of CO₂.

Vital capacity : (V.C) It is the total volume of air that can be expelled from the lungs after first filling the lungs to the maximum and then exhaling the same to the maximum :

VC = TV + IRV + ERV

= 500 + 2000 to 2500 + 1000 to 1500 = 3500 to 4500 ml.

Significance of V.C. : Vital capacity of a person gives important clues for diagnosing a lung problem. Measurement of this capacity helps the doctor to decide about the possible causes of the diseases and about the line of treatment. It determines the stamina of sportsmen and mountain climbers. The greater the vital capacity more is energy available to body. Sportsperson or mountain dwellers have higher vital capacity. Young persons have more vital capacity than aged.

The volume of air remaining in the lungs after a normal expiration is known as functional residual capacity (FRC).
It includes expiratory reserve volume (ERV) and residual volume (RV). It is calculated by the formula -: FRC = ERV + RV.
Where
ERV is the maximum volume of air that can be exhaled after a normal expiration. It is about 1000 mL to 1100 mL.
RV is the volume of air remaining in the lungs after maximum expiration. It is about 1100 mL to 1200 mL.
Thus 
FRC = ERV + RV
FRC = 1100 + 1200
FRC =  2300 mL
Functional residual capacity of the human lungs is about 2.1 - 2.3 L.

As altitude increases, the oxygen level in the atmosphere decreases. Therefore, as a man goes uphill, he will suffer from oxygen deficiency. This causes the amount of oxygen in the blood to decline. The respiratory rate increases to compensate for the decrease in the oxygen level of blood. Simultaneously, the rate of heart beat increases to increase the supply of oxygen to blood.

(a)

Transportation of carbon dioxide : It is transported in three forms :

1. In solution form : About 7% CO₂ dissolves in plasma and is transported as such.

(2) Through RBCs: About 20 – 25% of CO₂ is transported by the red blood cells as  carbaminohaemoglobin. Carbon dioxide binds to the amino groups on the polypeptide chains of haemoglobin and forms a compound known as carbaminohaemoglobin.
(3) Through sodium bicarbonate: About 70% of carbon dioxide is transported as sodium bicarbonate. As CO₂ diffuses into the blood plasma, a large part of it combines with water to form carbonic acid in the presence of the enzyme carbonic anhydrase. Carbonic anhydrase is a zinc enzyme that speeds up the formation of carbonic acid. This carbonic acid dissociates into bicarbonate (HCO3^–) and hydrogen ions (H⁺).

Inspiration is the process during which the atmospheric air is taken in.
Mechanism
The diaphragm and the set of intercostal muscles aid in the process of inspiration. The diaphragm contracts, thus increasing the volume of the thoracic cavity in the antero-posterior axis. The intercostal muscles also contract and lifts the ribs up further increasing the volume in the dorso-ventral axis. This creates a negative pressure in the lungs with respect to the atmospheric pressure. The air rushes in to equalise the pressure. 

pCO₂ has a major role in the transport of oxygen. 
Low pCO₂ and high pO₂ favours the formation of haemoglobin. At the tissues, the high pCO₂ and low pO₂ favours the dissociation of oxygen from oxyhaemoglobin. Hence, the affinity of haemoglobin for oxygen is enhanced by the decrease of pCO₂ in blood. Therefore, oxygen is transported in blood as oxyhaemoglobin and oxygen dissociates from it at the tissues.

Hypoxia - is a condition in which the body or a region of the body is deprived of adequate oxygen supply at the tissue level. It is caused by several extrinsic factors such as reduction in pO2, inadequate oxygen, etc.
Hypoxia may be classified as either generalised, affecting the whole body, or local, affecting a region of the body.

C.

C - alveoli - thin walled vascular bag - like structure for exchange of gases

C - Alveoli are thin - walled vascular bag -like structure for exchange of gases. A - trachea or windpipe is an air conducting tube through, which transport of gases takes place. B - pleural membrane is double layered, which reduces friction on the lung surface. D- diaphragm is involved in the inspiration and expiration process of breathing.

C.

C - vena cava - takes blood from body parts to right auricle, pCO₂ = 45 mmHg

A -  pulmonary vein takes impure blood from body part, pO₂ = 60 mmHg
B - Pulmonary artery - takes blood from heart to lungs, pO₂ = mmHg
C- Vena cava -takes blood from body parts to right auricle, pCO₂ = 45 mm Hg
D- Dorsal aorta takes blood from heart to body parts, pO₂ = 95 mm Hg

C.

Pneumonia

Empysema is a chronic respiratory disease where there is over-inflation of the air sacs(alveoli) in the lung, causing a decrease in the lung function and often, breathlessness. In this disease, the alveolar walls are damaged leading to drastic reduction in gas exchange. 

A.

Both A and B antigens on RBC but no antibodies in the plasma

Blood group AB is universal recipient because the person with AB blood group has both A and B antigens or RBC but no antibodies in the plasma. Other blood groups and their genotypes are

C.

Workers in grinding and stone-breaking industries may suffer, from lung fibrosis.

Irritating gases, fumes, dusts, etc., present in the work place result in lung disorders. Pneumoconiosis is a condition of permanent deposition of particulate matter in the lungs. Tissue reaction to these irritating substances causes proliferation of fibrous connective tissue called fibrosis. It is common in flour mill workers, iron mill workers, coal miners, stone grinders, etc.
A strong pneumotoxic signal from pons varoli reduces the inspiration duration to only 0.5 second while weak signal may prolong the inspiration duration to five seconds. 

D.

Lactate fermentation

B.

Rising CO₂ concentration

When we hold our breath, CO₂ concentration rises and accumulates in blood and lungs, triggering impulses from respiratory centre part of brain. The body has the ability to detect rising CO₂ levels and send signals to take a breath, so as to compensate the lowering levels of O₂ in blood and lungs. Gases diffuse from air to blood passively, i.e. from high concentration to low.
When lungs become concentrated with same CO₂ as in blood, it no longer leaves blood and keep rising till next birth. As one breathes in CO₂ diffuse out of lungs and oxygen is taken in. Thus, neutralising the acidity by high CO₂ levels.

D.

Epiglottis

The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It prevents the entry of food into the larynx, and directs it to the oesophagus. Due to improper movement of epiglottis, one may suddenly start coughing while swallowing some food.

A.

A: Alveolar cavity - main site of exchange of respiratory gases

Alveoli are the primary sites of exchange of gases. The exchange of gases (O2 and CO2) between the alveoli and the blood occurs by simple diffusion. 

D.

acts as a reserve during muscular exercises

Our tissue is able to utilise only 25% of O₂ carried by the arterial blood. The venous blood is still 75% saturated with O₂. This O₂ acts as a reserve during muscular exercise.

B.

One can breathe out air through eustachian tubes by closing both the nose and the mouth

A eustachian tube connects the middle ear cavity with the pharynx. The eustachian the pressure on either side of the eardrum (tympanic membrane).

A.

bicarbonate in blood plasma and RBCs

70-75% of CO₂ is transported as sodium bicarbonate (NaHCO₃) by plasma, and as potassium bicarbonate (KHCO₃) by RBCs.

C.

(4) 3500 mL,  (1) 1200 mL

Inspiratory Capacity (IC) is the maximum amount of air that can be inspired after a normal expiration, IC, = TV +IRV. It is 3600 mL in adult male and 2400 mL in the adult female. 
Residual Volume (RV) is the amount of air remaining in the lungs after a forced exhalation. Its average value is 1200 mL and 1000 mL in adult male and female respectively.

B.

fermentation

In fermentation, the incomplete oxidation of glucose is achieved under anaerobic conditions by a set of reactions, where pyruvic acid is converted to CO₂ and ethanol. The enzyme pyruvic acid, decarboxylase and alcohol dehydrogenase catalyse these reactions. In animals cells also, like muscles during exercise, where oxygen is inadequate for cellular respiration, pyruvic acid is reduced to lactic acid by lactate dehydrogenase. The reducing agent is NADH + H⁺, which is reoxidized to NAD⁺, in both the processes. 

C.

amphibolic

An amphibolic pathway is a biochemical pathway that serves both anabolic and catabolic processes. An important example of an amphibolic pathway is the Kerbs cycle, which involves both the catabolism of carbohydrates and fatty acid and the synthesis, eg alpha-ketoglutarate and oxaloacetate. 

D.

hydrophytes

In hydrophytes, vascular tissue and mechanical tissue are reduced. The cuticle is either completely absent or if present, it is thin and poorly developed. 
In xerophytes, cuticle is heavy, well -developed vascular tissue and mechanical tissue are well -developed and differentiated.

D.

Total lung capacity minus residual volume

Vital capacity is the sum of inspiratory reserve volume, tidal volume and expiratory reserve volume. It is about 4800 mL.
Total lung capacity is the sum of vital capacity and residual volume, ie, vital capacity minus residual volume.
Tidal volume is the amount of air, which normally passes into and out of the lungs during each cycle of quite breathing. It is about 800 mL in an adult person.
Inspiratory reserve volume is the extra volume of air that can be inhaled into lungs during deepest possible inspiration.

C.

inhalation of seasonal pollen

Asthma is a respiratory disorder. It is caused by foreign allergens and dust particles present in the air passing through it, the pollen grains present in air can cause asthmatic attacks in certain seasons. 

B.

atmospheric O₂ level is less and hence more RBCs are needed to absorb the required amount of O₂ to survive

At high altitudes, the atmospheric O₂ level is less and hence, more RBCs are needed to absorb the required amount of O2 to survive. That is why, the people living at sea level have around 5 million RBC/mm³ of their blood whereas those living at an altitude of 5400 meters have around 8 million RBC/mm³ of their blood.

B.

as bircarbonates

In our body, the blood transports the CO₂ in three ways:
(i) Majority of carbon dioxide produced (70%) in our cells is transported in the form of bicarbonates. In this way first, the CO₂ that dissolves in blood plasma reacts with water forming carbonic acid which dissociates into hydrogen and bicarbonate ions.

(ii) About 7% of all the CO₂ of transported by blood from tissues to the lungs is in dissolved state in plasma.
(iii) About 23% of CO₂, collected from cells through tissue fluids, is transported by blood in the form of carbamino compound, carbamino-haemoglobin (CO₂HHb).

A.

Residual Volume

Volume of air present in lungs after forceful expiration as residual volume which prevents the collapsing of alveoli even after forceful expiration.

B.

Silicosis

Silicosis is due to excess inhalation of silica dust in the workers involved grinding or stone breaking industries.

Long exposure can give rise to inflammation leading to fibrosis and thus causing serious lung damage.

Anthrax is a serious infectious disease caused by Bacillus anthracis. It commonly affects domestic and wild animals. Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased.

Botulism is a form of food poisoning caused by Clostridium botulinum.

A.

A.

Trachea

At its bottom, the trachea (another name for the windpipe) branches into two tubes called bronchi, which lead into the lungs.

The larynx is the voice box. It is connected to the windpipe. The oesophagus, like the windpipe, is a tube that runs through the neck. The lungs are the ballon like structure in the chest.

B.

Glycolysis

Glycolysis is an essential and first path of respiration. It is common in both aerobic and anaerobic respiration and occurs in the cytosol of all living cells of prokaryotes as well as Eukaryotes.

A.

Pons region in brain

Pneumotoxic centre which can moderate the functions of the respiratory rhythm centre is present in the pons region of the brain Neural signals from this centre can reduce the duration of inspiration and thereby alter the respiration rate.

D.

Cnidocytes

Cnidocytes or stinging cells are spherical or oval cells found in entire epidermis except that of basal disc and are found only in cnidarians other cells are found in sponges.

B.

Nature of the substrate

B.

Climacteric phenomenon

Ethylene is connected with the climecteric phenomenon in which there is a 1000 fold increase in the production of basal ethylene level during ripening of climacteric fruits.

B.

Glycolysis

Glycolysis is a common phase for aerobic and anaerobic respiration where 1 molecule of glucose (6 C)break down into 2 molecules of pyruvic acid (3 C).

B.

High temperature of the body

Fever increases metabolic activity by 7% per degree Celsius increasing the requirement of O₂. It increases the rate of breathing.

B.

Birds

It is the feature of birds (Aves) to have non-distensible lungs continuous with thin elastic air sacs.

B.

Baroreceptors

Carotid labyrinth or a gland is found at the base of internal carotid. It is probably a sense organ containing baroceptors that control blood pressure in the human body.

A.

More acidity in the blood

Oxyhaemoglobin behaves as a strong acid. As more and more oxyhaemoglobin forms in the lungs. it releases more and more H⁺ ions increasing the acidity of the blood. This is known as the Haldane effect.

B.

Simple diffusion

Oxygen diffuses from alveoli to deoxygenated blood, and carbon dioxide diffuses from deoxygenated blood to alveoli by simple diffusion. Diffusion is defined as, the flow of the substance (gases) from a region of their higher concentration to a region of lower concentration.

B.

150 ml

Dead space is the air that is inhaled by the body in breathing but does not take part in gas exchange. In man, it is 150 mL.

C.

Asthma

A.

Ephedra

Ephidrine is obatined from various species of Ephedra. It is used in the treatment of respiratory diseases, such as, Asthma, Cold, Bronchial congestion.

C.

contracts and flattens

Breathing or Respiration or Ventilation is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment. 

Breathing in is called inspiration or inhalation and breathing out is called expiration or exhalation. During inspiration, the diaphragm contracts putting backwards by partial flattening and increase the thoracic cavity lengthwise.

A.

vital capacity

Vital capacity is the amount of air which one can inhale and exhale with maximum effort. It is the sum of tidal voulme, inspiratory reserve volume and expiratory reserve volume.

VC = TV + IRV + ERV

     = 500 + 3100 + 1200

     = 4800 mL

D.

Pasteur effect

The rate of glycolysis increases because in anaerobic respiration the rate of ATP production is 2ATP per glucose mol. while in aerobic it is 38ATP per glucose so to compensate the increased ATP demand the rate of glycolysis increases.

A.

increase in number

At altitude the partial pressure of the oxygen decreases in atmosphere so there is less oxygen available to carry out respiration. In order to compensate the cellular oxygen demand, the body increases the amount of RBC present to trap as many oxygen molecules as possible.

B.

5000 ml

The vital capacity is the maximum amount of air that can be expelled from lungs by forced exhalation after a forced inhalation. It is equal to the sum of tidal volume (TV), inspiratory reserve volume (IRV) and expiratory reserve volume (ERV).
VC= TV+ IRV+ ERV
    = 500 + 3000 + 1100
    =4600 ml

D.

All of the above

Anaerobic Respiration is a process in which organisms produce energy in absence of oxygen. During anaerobic respiration, pyruvic acid forms ethyl alcohol (C₂H₅OH) and CO₂. This process is known as fermentation.

B.

6

Six turns of the Calvin cycle result in the production of one molecule of glucose.