Respiration: Meaning of Respiration, Types of Respiration, Transport of Oxygen and Carbon Dioxide (For CBSE, ICSE, IAS, NET, NRA 2022)

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Meaning of Respiration

  • Living organisms take in oxygen and give out carbon dioxide through the process.
  • The blood cells are responsible for carrying out the transport of gases during respiration both oxygen and carbon dioxide.
  • It is the biochemical process wherein the living cells of an organism produce energy.
  • The breakdown of glucose produces the energy (ATP-Adenosine triphosphate) .
Human Respiratory System

Types of Respiration

Cellular Respiration

  • It is a set of metabolic reactions occurring in all living cells to release energy.
  • This release of energy is due to the converting biochemical energy from nutrients into adenosine triphosphate- ATP.
  • The cellular respiration can be divided into Aerobic respiration and Anaerobic respiration based on the oxygen demand.

Aerobic Respiration

  • This respiration occurs in the presence of oxygen to produce energy.
  • This is a continuous process occurring within the cells of plants and animals.

Anaerobic Respiration

  • This respiration occurs in the absence of oxygen to produce energy.
  • The chemical equation can be represented as under:

Transport of Oxygen and Carbon Dioxide

Transport of Oxygen

  • The Red Blood Cells are responsible for transporting oxygen in the blood during respiration.
  • The pigment hemoglobin present in RBCs gives blood its red colour.
  • 97 % of oxygen is transported by Red Blood Cells in the blood.
  • The remaining 3 % of oxygen gets dissolved in the plasma.
  • When oxygen meets hemoglobin, it is known as Oxyhaemoglobin.
    • Depends on partial pressures of oxygen
    • Carbon dioxide
    • H + concentration
    • Temperature

Transport of Carbon Dioxide

  • The carbon dioxide is carried out by hemoglobin as carbamino-hemoglobin.
  • Around 7 % of the carbon dioxide is in a dissolved state in the plasma.
  • The remaining carbon dioxide is carried out as bicarbonate.
  • The partial pressure of carbon dioxide is high in the tissues.
  • Carbon dioxide gets dissociated from carbamino-hemoglobin in the alveoli where the partial pressure of oxygen is high.
  • The bicarbonates are responsible for releasing carbon dioxide at the alveoli formed at the tissues.
  • The deoxygenated blood (every 100 ml) can deliver carbon dioxide (4 ml) to the alveoli.

Oxidative Phosphorylation

  • ATP molecules are formed in the process.
  • Involving a series of electron carriers there is a transfer of electrons from NADH (nicotinamide adenine dinucleotide) or FADH2 (Flavin adenine dinucleotide) to O2.
  • This process takes place within the mitochondria of a cell.


Q 1. What are the two types of respiration involved in Cellular Respiration based on the oxygen demand?


The two types of respiration involved in Cellular Respiration based on the oxygen demand are:

i) Aerobic respiration

ii) Anaerobic respiration

Q 2. What is Respiration?

Answer: Respiration can be defined as the process of taking in oxygen and giving out carbon dioxide in all living organisms.

Q 3. Why living organisms need energy?


  • Energy is obtained from the food we eat.
  • The energy is required for different metabolic activities such as growth, development, repair, etc.

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