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Class 10, Science, Chapter-5, Lecture-3, Respiration (Notes)

RESPIRATION:

The biological process, which includes the mechanism of exchange of respiratory gases and the oxidation of digested food in cells to release energy, is termed as respiration.

BREATHING:

The physical process, by which an organism obtains oxygen from the environment and releases carbon dioxide, is termed as breathing.

DIFFERENCES BETWEEN:

RESPIRATION

BREATHING

1. Respiration is a biological process which involves breathing

1. Breathing is a physical process.

2. Energy is released during respiration.

2. No energy change takes place.

3. It takes place in the cells

3. It takes place through nose and lungs.

TWO TYPES OF RESPIRATION:

AEROBIC RESPIRATION:

The respiration which takes place in the presence of oxygen is termed as aerobic respiration.

Mechanism: 
The first step is the breakdown of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm without involvement of oxygen and 2 ATP molecules are produced. 
During aerobic respiration Glycolysis is followed by the Krebs Cycle
In Krebs Cycle, breakdown of pyruvate using oxygen takes place in mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of CO2. The other product is water. 36 ATP molecules are released in the process.

Step I– Glycolysis:
Glucose is converted to PYRUVATE in the CYTOPLASM in the absence of oxygen –
${{\rm{Glucose}}\,\buildrel {{\rm{in}}\,\,{\rm{cytoplasm}}} \over
\longrightarrow {\rm{Pyruvate}}\, + 2\,{\rm{ATP}}}$

Step II– Krebs Cycle: 
Pyruvate undergoes many changes through Krebs cycle and Electron Transport Chain (ETC) in the presence of O2 and finally produces CO2 , H2O and energy.
${{\rm{Pyruvate}} + {{\rm{O}}_{\rm{2}}}\buildrel {{\rm{in}}\,\,{\rm{Mitochondria}}} \over
\longrightarrow C{O_2} + {{\rm{H}}_{\rm{2}}}{\rm{O}} + {\rm{36ATP}}}$

Aerobic respiration provides 38 ATP of energy.

ANAEROBIC RESPIRATION:

The respiration which takes place in the absence of oxygen is termed as anaerobic respiration.

Mechanism:

The first step is the breakdown of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm without involvement of oxygen and 2 ATP molecules are produced. 
During anaerobic respiration, pyruvate may be converted into ethanol and carbo dioxide in plants. In animals, pyruvate gets converted into three-carbon molecule called lactic acid.

Step I– Glycolysis: 
Glucose is converted to PYRUVATE in the CYTOPLASM in the absence of oxygen –

Step II– 
Pyruvate undergoes fermentation in the absence of O2 and changes to

  • LACTIC ACID in animal cells
  • ETHYL ALCOHOL and CARBON DIOXIDE in plant cells

Anaerobic respiration provides 2 ATP of energy.

DIFFERENCES BETWEEN:

AEROBIC RESPIRATION

ANAEROBIC RESPIRATION

1. Utilises oxygen.

1. Does not utilise oxygen

2. End products are CO2 and H2O .

3. 38 ATP molecules are released

2. End product may be alcohol or lactic acid.

3. 2 ATP molecules are released

4. Occurs in cytoplasm and mitochondria

4. Occurs in cytoplasm only.

DIFFERENCES BETWEEN:

RESPIRATION

PHOTOSYNTHESIS

1. Glucose oxidises to produce CO2 and H2O

1. CO2 and H2O combine to produce Glucose

2. O2 is consumed and CO2 is released

2. CO2 is consumed and O2 is released.

3. Energy is released in the form of ATP

3. Solar energy is used.

4. Takes place throughout lifetime.

4. Takes place only in the presence of light.

5. Takes place in mitochondria

5. Takes place in chloroplasts

6. Takes place in all plants and animals

6. Takes place in green plants only.

COMMON FEATURES OF RESPIRATORY ORGANS:

  1. A large surface area to get enough oxygen
  2. Thin permeable walls for easy diffusion of gases
  3. Richly supplied with blood capillaries for quick transport of gases.

RESPIRATORY SYSTEM IN HUMAN BEINGS:

  1. External nostrils
  2. Nasal cavity (air is warmed, moistened and dirt particles are entrapped in the mucous)
  3. Internal nostrils
  4. Pharynx
  5. Larynx
  6. Glottis
  7. Epiglottis (covers the glottis while swallowing food and thus prevents food from entering into the windpipe)
  8. Trachea (supported by rings of cartilage that prevents it from collapsing when air is not present in it)
  9. Lung
    1. Bronchus
    2. Bronchiole
    3. Alveolus
  10. Diaphragm it separates thoracic cavity from abdominal cavity, and 
    it helps in breathing mechanism by its contraction and relaxation.

MECHANISM OF BREATHING IN HUMAN BEING:

  1. Inhalation-
    The diaphragm and muscles attached to ribs contract resulting into expansion of the thoracic cavity.
    Thus, air pressure decreases inside and air from outside rushes into lungs through nostrils, trachea and bronchi.
  2. Exchange of gases–
    Exchange of gases take place in the alveolar sac.
    Carbon dioxide from blood goes to alveoli of lungs.
  3. Oxygen from alveoli goes to blood.
  4. Exhalation–
    The diaphragm and rib muscles relax.
    The thoracic cavity comes to original size and the air is pushed out through bronchi, trachea and nostrils.

The rate of breathing increases from 15-18 times per minute to 20-25 times per minute during vigorous exercise.

Reason: 
During vigorous exercise, body cells need more energy. So, more oxygen is required for oxidation of glucose.

RESIDUAL VOLUME:

The amount of air that remains in the lungs after maximum exhalation to prevent lungs from collapsing and facilitate maximum absorption of oxygen by blood is termed as Residual Volume.