BIOLOGY 2 Marks Questions

A (v), B (vi), C (i), D (ii). E (iii), F (vii). G (iv).

Carbon monoxide gas comes out from the fireplace burning coal. The ability of carbon monoxide to combine with haemoglobin is approximately 250 times greater than the ability of oxygen. Carbon monoxide combines with haemoglobin to form a stable compound and this part of haemoglobin becomes useless for respiration. Therefore, a person feels suffocated and may even die.

Following are the five characteristics of the respiratory organs:
1. The surface of the respiratory organs being extremely thin so that they can exchange gases easily.
2. The respiratory surface always remains moist and a network of condensed blood cells is spread on the respiratory surface.
3. The respiratory surface is extremely wide and is involved in gaseous exchange.
4. Presence and carrying of pure air (oxygenated) to the respiratory surface.
5. Existence of respiratory tract for gaseous exchange and presence of respiratory pigment or haemoglobin as a carrier substance for carrying O₂.

For normal respiration, air reaches the lungs through the respiratory tract through the nose. The inner layer of the nasal passages secretes mucus, which has insecticidal nature. The hairs in the nasal passages prevent small insects and dust particles from entering. While breathing through the mouth, cold, dry air along with dust particles will pass through the cavity and enter the lungs. Such air can cause damage to the oral cavity and throat. Tonsils enlarge and the possibility of bronchitis increases. Gums and teeth may get damaged. There may also be damage to the Eustachian tube which may cause difficulty in hearing. Parasites of many types of diseases can enter the body.

Vital Capacity : The maximum amount (volume) of air that a person can inhale after forced inhalation. This includes ERV, TV and IRV or the maximum amount of air that a person can exhale after forced inhalation.
The partial pressure (in mm Hg) of O₂ and CO₂ on various parts involved in diffusion as compared to the atmosphere is as follows:

S.No.	Respiration	Atmospheric Air	Alveoli	Deoxygenated Blood	Oxygenated Blood	Tissue
1.	O2	159	104	40	95	40
2.	CO2	0.3	40	45	40	45

self

Respiratory diseases are as follows:
(i) Asthma (ii) Bronchitis (iii) Emphysema (iv) Occupational Respiratory Diseases
(i) Asthma: Asthma is a difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles.
(ii) Bronchitis This is an inflammation of the bronchi, the special symptoms of which are swelling and irritation in the bronchi, which causes continuous cough.
(iii) Emphysema: This is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. One of the major causes of this is cigarette smoking.

Due to increase in pCO₂, the liberation of O₂ from HbO₂ occurs easily and the O₂-Hb dissociation cycle gets shifted to the right. This is called Bohr's effect. This is considered an important factor in O₂ transportation. The reason for this effect is H⁺ obtained from organic acids. CO₂ dissolves with water to form H₂CO₃. This acid dissociates and produces H⁺.

Air comes in and out of the lungs only through the thin and flexible wall of the lungs. When the walls become thick, the lungs will not remain flexible and the ability of air to come in and out will be greatly reduced. Gas exchange occurs through the blood cells located in the thin wall of the lungs, due to which oxygen reaches the blood and CO₂ comes out. Therefore, due to the thick wall of the lungs, respiration will not be possible smoothly.

There is a special area called respiratory centre in the medulla oblongata of humans to control breathing. Through this, breathing is controlled. Due to damage to the respiratory centre located in the medulla oblongata of the human brain, respiration will not be possible. The contraction of the intercostal muscles of the ribs and relaxation of the radial muscles of the diaphragm will stop. As a result, the air filled in the lungs will come out and after some time the person will die.

Haemoglobin molecules contain four ferrous ions. Therefore, four molecules of oxygen can be combined with one molecule of haemoglobin, iron remains in its ferrous form. Therefore, this combination is called oxygenation.

Respiration : This process of exchange of atmospheric O₂ and CO₂ produced in cells is called breathing or respiration.
The stages of respiration are as follows:
(1) Respiration or pulmonary breathing by which atmospheric air is drawn in and alveolar air rich in CO₂ is released outside.
(2) Diffusion of gases (O₂ and CO₂) across the alveolar membrane.
(3) Transport of gases by blood.
(4) Diffusion of O₂ and CO₂ between blood and tissues.
(5) Use of O₂ by the cells for catabolic reactions and as a result generation of CO₂.