CBSE Class 10 Science Respiration Notes

RESPIRATION

7.1 RESPIRATION :

The sum total of all the vital activities is called as  metabolism. Vital act ivies refer to all the physiochemical activities of a cell. It has two aspects :

(i) Anabolism : It includes metabolic process by which complex cellular compounds are synthesized from simpler compounds, .e.g. Photosynthesis

(ii) Catabolism : It includes metabolic processes by which larger molecules are broken down into simpler molecules, e.g. Respiration. Respiration is an important catabolic process responsible for the production of energy.

7.1 (a) Definition :

The process by which assimilated food is oxidized and energy is released is called as respiration. In this process oxygen from air is taken in, this oxygen reacts with food molecules present in the body cells and burn them slowly to release energy. This energy is stored in the form of ATP molecules inside the cell for further use and the waste products i.e. CO₂ and H₂O are eliminated out of the body.

It is called as aerobic respiration.

NOTE : The process by which organisms obtain oxygen from environment and release carbon dioxide produced during oxidation of food to the outer environment is called as breathing. It is a part of respiration.

7.1 (b) Difference Between Breathing and Respiration :

(i) Breathing involves taking in  of oxygen and releasing out of carbon dioxide so it is a physical process while respiration is a biochemical process which, along with breathing involves oxidation of food.

(ii) Breathing involves lungs so it is an organ system level process while respiration besides being at organ system level, also occurs at cellular level.

(iii) Breathing itself do not release energy while respiration results in the release of energy which is then stored in from of ATP.

(iv) Breathing is a part of respiration while respiration is not a part of breathing but it involves breathing.

7.1 (c) Types of Respiration:

(i) External respiration: Exchange of gases between an organism and its environment.

(ii) Internal respiration: Exchange of gases between tissue cells and extra cellular environment.

(iii) Aerobic : When oxidation of food takes place in presence of molecular oxygen. it is called as aerobic respiration.

(iv) Anaerobic respiration: When oxidation of food material does not require molecular oxygen or it occurs in absence of molecular oxygen,it is called as anaerobic respiration.

7.1 (d) Respiration:

Respiration in divided in three parts:

(i) Cellular respiration                     (ii) Respiration in plants                 (iii) Respiration in animals

7.1 (e) Respiration Plants :

1. In plants exchange of gases takes place from leaves, stems and roots individually.
2. Transfer of respiratory gases from one part to another is very less.
3. Exchange of gases in plants occurs by simple diffusion.

(i) Respiration in roots:

1. In young roots, the epidermal cells are extended to form root hair. These root hair remain in direct in contact with the air present in between the soil particles. The oxygen from this air enters into the root hairs by simple diffusion and reaches to other cells of root for respiration.
2. In older roots a protective layer of dead cells is present which have tiny openings called as lenticels. Diffusion of oxygen takes place through these pores and carbon dioxide is released out through the same.

(ii) Respiration in stem:

1. In herbaceous plants, stem have small openings in their epidermal cells called as stomata, the oxygen from air enters through stomata and carbon dioxide is released from the same.
2. In hard and woody stems of big plants and trees, lenticels are present in place of stomata through which exchange of gases takes place.

(iii) Respiration in leaves:

1. Surface of leaves possess numerous tiny pores called as stomata in their epidermal cells, exchange of gases takes place through stomata and when CO₂ concentration in cell increases stomata opens and CO2is released out.
2. An experiment to show that plants take oxygen and evolve carbon dioxide during respiration :
3. Experiment : To demonstrate the plants take oxygen and evolve dioxide during respiration set the apparatus according to figure by taking KOH in U-tube, lie-water in two wide mouth bottles, one potted plant, bell jar and black-cloth. During day time the potted plant is covered with black-cloth to check photosynthesis. Make the apparatus airtight and start the aspirator. After sometime you will find that the lime water of second bottle turns milky. The explanation for this is that when the water comes out from aspirator, the atmospheric air enters into the apparatus through the second end and passes through the U-tube containing caustic potash into the tube containing lime water. The caustic potash absorbs the CO₂ of the air. Thus, CO₂ free air reaches into lime water so it does not turn milky. If indicates the air does not contain even trace of CO2. When this air reaches into the lime water of second tube through a bell jar having potted plant covered with black cloth to check photosynthesis, it turns milky. It proves that CO₂ is evolved during respiration.

7.2 RESPIRATION IN ANIMALS:

1. Respiration in animals takes place as a single unit, the have different types of organs for respiration due to which mode of respiration also varies according to the organism but the basic mechanism is same.
2. From phylum Protozoa to Ctenophore respiration is by generally body surface, in phylum Plathyelminthes to Nematodes are mostly anaerobic and endoparasites, in phylum Annelida cutanous membrane occurs and then from phylum Arthropoda till Mammals various respiratory organs were developed like trachea, gills and lungs.

Type of respiration                           Organs involved                                 Example

1. Cell surface respiration         General body surface                       Amoeba, Paramecium
2. Tracheal respiration               Trachea and tracheoles                         Insects
3. Branchial respiration                 Gills                                                 Fishes
4. Cutaneous respiration                Skin                                                  Frog
5. Pulmonary respiration               Lungs                                           Amphibians, reptiles, birds
6. Buccal respiration                   Buccal cavity                                         From

 Some important characteristics of respiratory organs of animals are:

1. They have large surface area to get enough oxygen.
2. They have thin walls for easy diffusion and exchange of gases.
3. They have rich blood supply for transport of respiratory gases.

7.2(a) Respiration in Amoeba:

In unicellular organisms like amoeba and in some lower multicellular animals likes sponges and cnidarians, respiration or exchange of gases occurs through general body surface as these cells are in direct contact with an aquatic environment so the oxygen dissolved in water diffuses into the cell and brings about oxidation of food, at the same time carbon dioxide released is expelled out of the cell by the same process.

7.2(b) Respiration in Earthworm

In organisms like earthworm and leech exchange of gases occur through their skin as their skin is very thin and most. It is rich in blood supply so the oxygen is absorbed by moist skin of earthworm and is transported to all the cells of body through blood. The carbon dioxide from body cells diffuses into the blood and expelled out through skin.

7.2 (c) Respiration in Fish:

(i ) In fish exchange of gases occurs through gills so the respiration is said to be branchial.

(ii) Gills are present on both the sides of its head, they are covered by gill covers.

(iii) During breathing fish takes in water through its mouth and pass it over the gills, the oxygen present in water extracted by gills and water is removed out through gill slits. This oxygen is now absorbed by blood and carried to all parts of the body and at the same time carbon dioxide is released into the blood and comes back to the gills and is expelled out into the surrounding water.

(iv) Same type or respiratory pattern is followed in some other aquatic organisms like prawns.

7.2 (d) Respiration in Grasshopper:

(i) In insects there occurs a system of tiny holes and air tubes all over the body these tiny holes or openings are called as spiracle. This whole system facilities the exchange of gases and is called as tracheal system.

(ii) During breathing oxygen of air enters the spiracle and reached to each and every part of grasshopper’s body through trachea and tracheoles and carbon dioxide produced during respiration is carried back by trachea and tracheoles to the spiracles and is expelled out of the body of insect.

(iii)The same mechanism is followed in other insects like houseflies, mosquitoes, bees etc.

7.2 (e) Respiration in Humans:

Human respiratory tract

(i) External nostrils: First part of respiratory system. It opens into nasal cavity and is meant for inhalation of air from outside.

(ii) Nasal cavity: This cavity is separated from oral cavity by means of a hard and bony palate. It is lined by ciliated columnar epithelial cells that are rich in mucus; it brings about warming, moistening and sterilization of air. It contains hair and mucus which entrap the dust particles.

(iii) Internal nares: Nasal cavity opens into it and it leads to pharynx.

(iv) Pharynx: It is a common part between both alimentary canal and respiratory system.

(v) Larynx: It is an enlarged part of trachea which is also called as ‘voice box’. It produces voice by passage of air between vocal cords. It contains four different types of cartilages among them a ‘c’ shaped thyroid cartilage protruding out  in neck region is called Adam’s apple.

(vi)Trachea: also called wind pipe. It is 10-12 cm long tube. It’s walls are supported by 16 - 20 ‘c’ shaped cartilaginous rings which percent them to collapse when air is absent in them

(vii) Bronchi: Trachea is branched into two bronchi left and right each of which enters into the lungs.

(viii) Lungs: These are two light weight spongy pouches covered by a membrane called Pleura. Bronchi are further branched into several bronchioles, at the end of bronchioles alveolar sacs or alveoli are present which are rich in blood capillaries and thin walled.

(vi) Diaphragm : It is a sheet of muscles that lies below the lungs and separates thoracic cavity from abdominal cavity.

Mechanism of breathing: It includes

(i) Inhalation: When air is breathed in, the diaphragm and muscles attached to the ribs contract due to which there occurs expansion of chest cavity, it results increase in volume of chest cavity thus the air pressure decreases and air from outside rushes into the lungs and alveolar sacs get filled with air containing oxygen. The oxygen present in air diffuses into the blood and CO₂ from blood diffuse out into alveolar sac.

(ii) Exchange between blood and tissues: CO₂ is taken by blood and O₂ diffuses into tissues.

(iii) Exhalation: When air is breathed out the diaphragm and muscles attached to ribs relax, which brings about contraction in chest cavity, its volume gets reduced and CO₂ is pushed out from lungs into the air through trachea and nostrils.

8.1 MACHANISM OF GASEOUS EXCHANGE BETWEEN TISSUES AND BLOOD :

When the air enters into the lungs through nostrils, trachea and bronchi it enters into the bronchioles, from bronchioles it moves into thin walled alveolar sacs or alveoli. Alveoli are rich in blood capillaries, at this place oxygen from air diffuses into the blood and reaches to all the cells and tissues of body this oxygen now diffuses into the cell and is utilized for the oxidation of food and production of energy in mitochondria as a result of this carbon dioxide is produced in cells, due to this increased concentration of CO2, it diffuses into the blood and is brought back to alveoli and expelled out of the lungs through trachea and nostrils.

8.1 (a) Control of Respiration:

Respiration is controlled by the respiratory centre situated in medulla oblongata of brain.

(i) Breathing occurs involuntarily.

(ii) Under normal conditions rate of breathing is 15-18 times per minute. During vigorous exercise the demand for oxygen increases due to which rate of breathing increases by about 20-25 times.

(iii) The total area for gas exchange covered through 300 million alveoli is about 36-72 m2 in each lung.

(iv) Respiratory quotient: It is defined as the ratio of the volumes of CO2 liberated and O2 used during respiration.

8.1 (b) Some Respiratory Disorders:

1. Emphysema: It occurs due to infection, smoking etc. It occurs due to obstructions in bronchioles caused by breaking of alveolar septa. Bronchodilators and O2therapy are used, for curing this disease.
2. Asthma: Air passages are narrowed and lead to obstruction in breathing.
3. Pneumonia: Lymph and mucous accumulate in alveoli and bronchioles. It occurs due to bacterial and viral infection.
4. Bronchitis: Swelling in living membranes of respiratory tract due to excessive smoking.
5. Tuberculosis: Bacterial infection in lungs.
6. Pleurisy: Inflammation of lung membrane called as pleurisy.
7. Sudden contraction of diaphragm along with loud closure of glottis causes Hiccough.
8. Sudden and violent expulsion of air through mouth and nose is called a sneezing.
9. Fermentation: the slow decomposition of organic matter into simpler substances in the presence of enzymes is known as fermentation. This process is used for preparation of alcoholic beverages in presence of yeast in the absence of oxygen. Glucose and fructose are converted to ethanol by this process. It is a type of anaerobic respiration.

8.1 (c) Difference Between Aerobic and Anaerobic Respiration :

8.1 (d) Differences Between Respiration and Photosynthesis:

8.1 ( e) Differences Between Respiration and Combustion :

8.1 (f) Cellular Respiration :

If refers to the oxidation of food taking place inside the cell. As this process is at cellular level so it is called cellular respiration. It takes place in three steps :

It refers to the oxidation of food taking place inside the cell. As this process is at cellular level so it is called cellular respiration. It takes place in three in 3 steps :

(i) Glycolysis                                       (ii) Kreb Cycle                                     (iii) Electron Transport System

8.1 (g) Glycolysis :

 Glycolysis also called EMP pathway, site-cytoplasm of cell.

(i)  In this cycle glucose is converted into pyruvic acid in presence of many enzymes and co-enzymes.

(ii) Oxygen in not required during glycolysis.

(iii) 1 molecule of glucose gives rise to 2 molecules of pyruvic acid.

(iv) In this process 4 molecules of ATP are formed among them 2ATP molecules are utilized thus net gain of ATP is two molecules.

(v) 2NADP molecules are reduced to 2NADPH2 , which later produces 6ATP molecules.

(vi) Overall production of ATP in glycolysis is 2ATP + 6ATP = 8ATP

(vii) There is no production of CO₂ during this process.

NOTE : After glycolysis, pyruvic acid is converted into acetyl Co-A with the release of CO₂ and the process is called as ‘oxidative decarboxylation’. It occurs in mitochondria of the cell. Besides this 6ATP are also formed during this step.

8.1 (h) Kreb Cycle :

Site : Mitochondria of cell

(i) Also called aerobic oxidation.

(ii) Discovered by Sir Hans Kreb.

(iii) Another name TCA cycle (tricarboxylic acid cycle) or Citric acid cycle.

(iv) It brings about the conversion of pyruvic acid, fatty acids, fats and amino acids into CO₂ and water by oxidation.

(v) It is the common path for oxidation of carbohydrates, fats, proteins.

(vi) it accounts for 24ATP molecules.

(vii) It starts with acetyl Co-A which is then converted into several intermediate compounds with the release of NADPH₂, FDH₂, ATP, hydrogen atoms and then Acetyl Co-A is regenerated back.

8.1 (i) Electron Transport System or ETS :

(i)  In this hydrogen atoms produced during oxidation of various intermediates during Kreb cycle are first broken into protons and electrons.

(ii) These protons and electrons after passing through a series of coenzymes and cytochromes combine with oxygen to form water molecules.

(iii) During these series of events 1NADPH₂ releases 3ATP molecules and 1FADH₂ gives 2ATP molecules which were produces during kreb cycle and glycolysis.

NOTE : The net gain of ATP molecules during respiration in 38ATP molecules among them,

8ATP from glycolysis

6ATP from conversion of pyruvic acid into acetyl CO. A

24ATP from kreb cycle

besides this CO₂ and H₂O are also released.

Some important points :

(i)  Diaphragm becomes flat during inspiration and becomes convex during expiration.

(ii) Tidal volume : Volume of air inspired or expired in relaxed position. It is around 500 ml.

(iii) Residual volume : Air left in the whole reparatory tract after forceful expiration. It is 1.5 liters.

(iv) Total lung capacity : Maximum amount of air the lungs can hold after forceful inspiration. It is about 5-6.0 litres.

(v) Vital capacity : Maximum amount of air which can be breathed out through forceful expiration after a forceful inspiration. It is 3.4-4.8 litres.

1. Vital Capacity is more in athletes, mountain dwellers, non smokers.
2. The total area for gas exchange provided by our 750 million alveoli in two lungs in 100 S. m.
3. In the cycle of inhalation and exhalation, repeated 15 to 18 times in a minutes about 500 ml of air is breathed in and out. In 24 hours, we breadth in 1500 litres of air.
4. Blood is the medium for the transport of oxygen from the respiratory organ to the different tissues and carbon dioxide from tissues to the respiratory organs. As much as 97 percent of the oxygen is transported from the lungs to the tissues in combination with hemoglobin and only 2 percent is transported in dissolved condition by the plasma.
5. A normal person has about 15 grams of hemoglobin per 100 ml of blood. One gram of hemoglobin binds about 1.34 ml of O₂. Thus, 100 ml of blood carries about 20 ml of oxygen.
6. Carbon dioxide is also transported by hemoglobin. When a respiring tissue release carbon-dioxide, it is first diffused in the plasma. From here it diffuses into the red blood cells. Carbon-dioxide is transported from the tissues to the lungs in the form of bicarbonates dissolved in water.
7. About 23% of carbon dioxide entering into the erythrocytes combines with the globin (protein) part of haemogloin to form carbaminohaemoglobin, which is transported to the lungs.
8. Carbon monoxide binds with hemoglobin about 230 times more readily than oxygen. When a person inhales carbon monoxide, it diffuses from the alveolar air to the blood and binds to haemoglobin forming carboxyhemoglobin. The latter is a relatively stable compound and cannot bind with oxygen molecules. So, the amount of hemoglobin available for oxygen transport is reduced. The resulting deficiency of oxygen cases headache, dizziness, nausea and even death.
9. Mountain sickness : It is also known as altitude sickness. At sea level the concentration of oxygen is about 21% and the barometric pressure averages 760 mm Hg. As altitude increases, the concentration remains the same but the number of oxygen molecules per breath is reduced. AT 12,000 feet the barometric pressure is only 483 mm Hg, so there are roughly 40% fewer oxygen molecules per breath. In order to oxygenate the body effectively, breathing rate (even while at rest) has to be increased. This extra ventilation increases the oxygen content in the blood, but not sea level concentration. The fall in oxygenation of blood produced the symptoms of mountain sickness. These symptoms include breathlessness, headache, dizziness, nausea, vomiting, mental fatigue and a bluish tinge on the skin, nails and lips.