Respiration in organisms

Start music   Jan 4 2017 || 11:02 PM

Respiration in organisms


Cellular respiration

It is the process of breakdown of food in the cell with the release of energy

Cellular respiration takes place in the cells of all organisms


Aerobic respiration

  • In the cell, the food (glucose) is broken down into carbon dioxide and water using oxygen
  • When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration



Glucose (with the use of O2)à Carbon dioxide + water +energy





Anaerobic respiration

  • Food can also be broken down, without using oxygen.
  • This is called anaerobic respiration
  • Organisms such as yeast can survive in the absence of air. They are called anaerobes.

Glucose (without the use of O2)à Carbon dioxide + alcohol +energy





  • Our muscle cells can also respire anaerobically, but only for a short time.
  • This happens during heavy exercise, fast running, cycling, or heavy weight lifting
  • Here the demand for energy is high but supply of O2 to produce the energy is limited



Glucose (absence of O2)à Lactic acid +energy





  • Accumulation of lactic acid causes muscle cramps
  • Any increase in the supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water



  • Taking in air rich in O2 (inhalation) & giving out air rich in CO2 (exhalation)
  • The percentage of O2 and CO2 in inhaled are 21% and 0.04% respectively
  • The percentage of O2 and CO2 in the exhaled air are 16.4% and 4.4% respectively
  • The number of times a person breathes in a minute is termed as the breathing rate
  • On an average, an adult human being at rest breathes 15-18 times in a minute.
  • During heavy exercise, the breathing rate can increase up to 25 times per minute


Lungs and Chest cavity

  • Lungs are present in the chest cavity, surrounded by ribs on the sides
  • A large, muscular sheet called diaphragm forms the floor of the chest cavity


Mechanism of breathing

  • When we inhale air, it passes through our nostrils into the nasal cavity
  • From the nasal cavity, the air reaches our lungs through the windpipe
  • During inhalation, ribs move up and outwards and diaphragm moves down
  • This movement increases the volume in our chest cavity for air to fill in
  • During exhalation, ribs move down and inwards, while diaphragm moves up to its former position
  • This reduces the size of the chest cavity and air is pushed out of the lungs


Breathing in other animals


  • Have small openings called spiracles on the sides of its body
  • Have a network of air tubes called tracheae for gas exchange



  • Breathe through their skins which is moist and slimy



  • They have lungs, yet they can still breathe through their skin



  • They have gills which are supplied with blood vessels, which can help them breathe O2 dissolved in water


Respiration in plants

  • They also take in O2 from air and give out CO2 like humans




Source - Slideshare