Class 11 Biology Ch 17 Breathing And Exchange of Gases Important Points to remebered

 Welcome student, today we will mention Class 11 Biology Ch 17 Breathing And Exchange of Gases Important Points to remember, it will cover the whole NCERT, and best for revision, and prepared by the masters of their field. 

Class 11 Biology Ch 17 Breathing And Exchange of Gases Important Points to remember

Points To Remember:-

Breathing : (External respiration) The process of exchange of O2 from

the atmosphere with CO2 produced by the cells.

Carbamino haemoglobin: Compound formed in RBCs when CO2 combine

with haemoglobin.

Inspiration: Oxygen from fresh air taken in by lungs and diffused into the

blood.

Expiration: CO2 given up by venous blood in the lungs is sent out to the exterior.

Respiration: The sum total of physical and chemical processes by which

oxygen and carbohydrates (main food nutrient) etc are assimilated into the system

and the oxidation products like carbon dioxide and water are given off.

Diaphragm: A muscular, membranous partition separating the thoracic

cavity from the abdominal cavity.

Hypoxia—Shortage of oxygen in tissues.

Partial Pressure—The pressure contributed by an individual gas in a mixture

of gases. It is represented as pO2 for oxygen and pCO2 for carbon dioxide.

Pharynx: The tube or cavity which connects the mouth and nasal passages

with the oesophagus. It has three parts (i) Nasopharynx (anterior part) (ii) Oropharynx

(middle part) and (iii) Laryngopharynx (the posterior part which continues to the larynx)

Adam’s Apple: The projection formed by the thyroid cartilage and surrounds

the larynx at the front of the neck.

Tidal volume (TV): Volume of air taken in/given out during normal

respiration (500 mL.)

Inspiratory Reserve Volume (IRV): Additional volume of air inspired by

a forcible inspiration. 2500mL to 3000mL.

Expiratory Reserve Volume (ERV): Additional volume of air, a person

can expire by a forcible expiration.

Residual volume (RV): Volume of air remaining in the lungs even after a

forcible expiration (1100 mL to 1200 mL)

PULMONARY CAPACITIES: -

Use in clinical diagnosis.

Inspiratory capacity (IC) = (TV + IRV) Total volume of air a person can

inspire after a normal expiration.

Expiratory Capacity—Total Volume of air a person can expire after a

normal inspiration E.C. = TV + ERV

Functional Residual Capacity—Volume of air that will remain in lungs

after a normal expiration (FRC) = (ERV + RV)

Vital Capacity (VC) = (ERV + TV + IRV) or the maximum volume of air

a person can breathe out after a forced inspiration.

Total Lung Capacity: It includes RV, ERV, TV and IRV or vital capacity

+ residual volume.

Pulmonary—Anything associated with the lungs is given the prefix

‘pulmonary’

Steps involved in respiration—

(i) Breathing or pulmonary ventilation (intake of atmospheric air and releasing

out CO2 rich alveolar air)

(ii) Diffusion of gases (O2 and CO2

) across alveolar membrane & blood vessel

(capillaries).

(iii) Transport of gases by the blood.

(iv) Diffusion of O2 and CO2 between blood and tissues.

(v) Utilisation of O2 by the cells for catabolic reactions and resultant release of

CO2.

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Respiratory Tract :

 A pair of external nostrils → nasal chamber through nasal passage → pharynx

→ glottis → larynx → trachea → Left and right primary bronchi → secondary

and tertiary bronchi → bronchioles → vascularised bag like structures

(alveoli) or air-sacs. Each lung is covered with a double-layered membrane

known as pleura with pleural fluid between them.

Respiratory organs in animals :

(i) Protozoans, annelids Frogs—Body surface

(ii) Fishes, tadpole stage of frog and many other aquatic animals—Gills (Branchial

Respiration)

(iii) Insects and a few other arthropods—Tracheal tubes

(iv) All land vertebrates (amphibians, reptiles, aves and mammals)—Lungs.

(Pulmonary Respiration)

Conditions required for (cutaneous respiration)

The skin should be moist and thin. It should be highly vascularised.

Physiology of Respiration :

(a) Exchange of gases—Diffusion of gases takes place from the region of higher

partial pressure to lower (lesser) partial pressure)

 (i) pO2 in alveolar air = 104 mm Hg.

 (ii) pO2 in venous blood = 40 mm Hg.

 O2 diffuses from alveoli to venous blood.

 (iii) pCO2 in venous blood = 45 mm Hg.

 pCO2 in alveolar air = 40 mm Hg.

 CO2 diffuses from venous blood to alveoli

(b) Transport of O2 by the blood — (i) About 3% of O2 in a dissolved state

through plasma.

 (ii) As oxyhaemoglobin: 97% of O2 diffuses from plasma into RBCs.

Haemoglobin carries 1-4 molecules of O2.

 Hb4 + 4O2

LUNGS

TISSUE

Hb4 O8

Oxyhaemoglobin

Oxygen dissociation curve

• A sigmoid curve showing the relationship between the % of saturation of

haemoglobin with oxygen in blood and pO2 of the blood.

• Fully saturated each gram of haemoglobin combined with nearly 1.34 ml of

oxygen.

• H+ concern., CO2 tension, temperature affects the curve. An increase in their

concentration decreases the affinity of haemoglobin for oxygen.

(c) Transport of CO2

(i) As a solution – 7% of CO2 dissolves and is carried by the plasma.

(ii) As Bicarbonate – 70% of CO2 in RBCs combines with water from carbonic

acid. Carbonic acid dissociates into bicarbonate ions and H+, Carbonic

anhydrase enzyme help in these reactions.

 CO2 + H2O H2CO3 HCO–

3

Carbonic + H+

anhydrase

Carbonic

anhydrase

(iii) As carbaminohaemoglobin – 23% CO2 combines in RBC with an amino group

of haemoglobin, form carbaminohaemoglobin.

Regulation of Respiration

• Respiratory rhythm centre in the medulla of the brain responsible for this regulation.

• Pneumotaxic centre in pons region moderates function of respiratory rhythm

centre.

• Chemosensitive area adjacent to rhythm centre is highly sensitive to CO2

and H+ ions.

• Increase in CO2 and H+ ions activates this centre, which in turn signal the

rhythm centre to make necessary adjustments and the respiratory process by

which these substances can be eliminated. 

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