Respiration:

• Respiration is the biochemical process in which the cells of living organisms obtain energy by combining oxygen and glucose, resulting in the release of carbon dioxide, water, and ATP.

C₆H₁₂O₆ + 6O₂  → 6CO₂ + 6H₂O + ATP

• Diverse organisms use oxygen to break-down glucose completely into carbon dioxide and water.
• The oxidation of glucose provides energy required for all cellular activities.
• In the absence of glucose, the cells break down proteins and fats to produce glucose. Further oxidation of this glucose fulfil the respiratory needs of the cell.
• At first, the six carbon glucose is broken down into two molecules of three carbon pyruvate (C₃H₄O₃). This process takes place in the cytoplasm.
• Cellular respiration takes place in mitochondria. That’s why mitochondria are also known as the powerhouse of the cell.

Difference between breathing and respiration:

Breathing	Respiration
It is a physical process.	It is a biochemical process.
In this process, we inhale and exhale air in and out of our lungs.	In this process, oxygen is used to breakdown Glucose in order to generate energy.
It involves taking in oxygen from the environment and removal of carbon dioxide from the body.	In this process chemical energy stored in the food is released in the form of ATP along with carbon dioxide and water.
Breathing takes place in the respiratory organs called as lungs.	This takes place in the cells.
It is a voluntary process.	It is the involuntary process.
Breathing involves respiratory organs and the cells called as alveoli.	It involves cells in the body and their organelles.

 

Types of respiration:

Different living organisms respire in different ways. Based on their respiration process either in presence or absence of oxygen there are two types of respiration:

Anaerobic respiration:

• The respiration which takes place in absence of oxygen is called anaerobic respiration.
• Also, we can say it is the process of producing cellular energy without oxygen.
• There is no release of water in this process.
• Anaerobic respiration is a relatively fast reaction and produces 2 ATP, which is much less than aerobic process.
• Some examples include alcohol fermentation, lactic acid fermentation and in the decomposition of organic matter.

Glucose + Enzymes = Carbon Dioxide + Ethanol / Lactic acid

Aerobic respiration:

• Aerobic respiration is the breakdown of glucose in the presence of oxygen.
• This type has end products carbon dioxide, water and energy.
• The amount of energy released in aerobic respiration is very high i.e. 686 kcal or 38 ATP of chemical energy and 420 kcal of heat energy.
• Aerobic respiration is carried out in two stages that are: Glycolysis and Krebs cycle.
• It is mainly seen in multicellular organisms such as animals, plants, humans, several bacteria, fungi etc.

Difference between aerobic and anaerobic respiration:

Aerobic Respiration	Anaerobic Respiration
The respiration which takes place in the presence of oxygen is aerobic respiration.	The respiration which takes place in the absence of oxygen is anaerobic respiration.
The end products of aerobic respiration are carbon dioxide and water.	The end products of anaerobic process are carbon dioxide and ethanol or lactic acid.
In this process our brain receives energy.	This process helps in fermentation of yeast to produce ethyl alcohol or ethanol in the beverage industry.
Aerobic respiration is carried on in two stages call glycolysis and Krebs cycle.	Anaerobic process is also carried on in two stages called glycolysis and fermentation.
This type of respiration is mainly in multicellular organisms such as animals, plants, humans, etc.	Anaerobic respiration is mainly seen in unicellular organisms like bacteria, fungi, protozoa, etc.
Aerobic respiration which is carried out in the lungs of humans, animals are called pulmonary respiration.	Anaerobic respiration uses bacteria such as lactobacillus to convert pyruvic acid into lactic acid. This bacteria commonly used for making curd or yogurt.

Respiration in plants:

 

 

• Every part of a plant carries respiration process.
• Stems, leaves and roots respire at very lower rate as compared to animals.
• The leaves of plants have tiny pores on their surface which are called stomata. Plants exchange gases by diffusion through the stomata during respiration.
• Oxygen from the air diffuses into a leaf and reaches all the cells.
• During respiration carbon dioxide produced is released into the air through the stomata.
• Plants respire during the day as well as during the night.
• During the day, plants respire the same oxygen produced during photosynthesis and the extra amount of oxygen is released through the stomata.
• The air present in the soil is taken up from roots.
• In stems, from either stomata or lenticels, the exchange of gases takes place.

Respiration in animals:

• In simple unicellular animals like Amoeba, respiration takes place by the simple diffusion of gases through the cell membrane.
• Earthworms use their skin to absorb oxygen from air and release carbon dioxide. So, skin is the respiratory organ in the earthworm.
• Fish, prawns and mussels are the aquatic animals which have gills as the respiratory organs. Gills absorbs oxygen dissolved in water and releases carbon dioxide out of the body.
• In the insects like grasshopper, cockroach, housefly and a mosquito, the tiny holes called spiracles on their body and the air tubes called tracheae are the respiratory organs.
• The land animals such as man (humans), birds, lizard, dog and frog etc. respire through the lungs. However, Frogs breathe both by lungs and skin.

Human Respiratory System:

The respiratory system in human beings consists of the nose, pharynx, larynx, trachea, bronchi, alveoli and pair of lungs.

• Air enters the body through nostrils.
• The air passing through the nostrils is filtered by fine hairs present inside the nostrils.
• Nostrils are also lined with mucus which prevents dust particles to enter inside.
• From here, it goes to pharynx which is a common passage for both the respiratory and digestive system. After that, it moves into the larynx (voice box).
• In the throat (trachea, which also known as wind-pipe and is 10-12 cm long tube with a diameter of 2-3 cm) there are rings of cartilage which ensures that the air-passage does not collapse.
• From here, the air passes through the throat and into the lungs.
• The lungs, which are a pair of spongy and elastic respiratory organs protected by a bony rib-cage.
• Inside lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures called alveoli.
• The role of alveoli is to provide a surface where the exchange of gases can take place.
• The surface of the alveoli is reached with the extensive network of blood vessels.
• As air enters the lungs through nostrils, alveoli gets filled with air.
• The blood vessels present in alveoli absorbs all the oxygen.
• Haemoglobin (Present in RBC) present in blood has a great affinity towards oxygen.
• From here oxygen is transported to all the cells in the body.
• The blood brings carbon dioxide from the rest of the body cells and releases it into the alveoli.
• When there is breathing process, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.
• As we know that carbon dioxide is more soluble in water than oxygen and hence is mostly transported in the dissolved form in our blood.

Also read,
Life processes
Nutrition in plants	Nutrition in animals
Respiration in plants	Control and coordination
Transportation in plants	Human circulatory system
Excretion