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Transport of Oxygen and Carbon Dioxide through Respiration

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An Introduction

Respiration is an essential mechanism of the human body as it is responsible for producing energy. Subsequently, it helps to convert food into chemical energy to facilitate cellular activities.

Furthermore, it is responsible for supplying oxygen to cells and eliminating carbon dioxide from the system. Keeping these in mind, let’s proceed to find out respiration and the process of transport of oxygen and carbon dioxide in brief.

What is Respiration?

It is a catabolic process wherein living organisms inhale oxygen and exhale carbon dioxide, enabling the body to release required energy. Notably, the transport of gases takes place in blood cells.


Needless to say, the active transport of gases in blood cells depends mostly on the respiratory organs. For instance, pharynx, trachea, soundbox, bronchi, bronchioles, alveoli, etc. have a significant role in the human respiratory system.

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Test Your Knowledge:

_________ is responsible for the transport of respiratory gases.

  1. Digestive system

  2. Reproductive system

  3. Respiratory system

  4. Skeletal system.

Steps of Respiration

Several steps have to be completed to initiate and complete the transportation and diffusion process.

Following pointers highlight the carbon dioxide and oxygen transport steps in respiration.

  1. Pulmonary ventilation or breathing, which helps to draw in the atmospheric air and also allows releasing the carbon dioxide-rich air out.

  2. Diffusion of oxygen and carbon dioxide in the alveolar membrane.

  3. Transport of gases in blood.

  4. Transport of oxygen and carbon dioxide in blood cells and tissues.

  5. Absorption of oxygen by cells to initiate catabolic reactions.

  6. Release of carbon dioxide or cellular respiration

DIY: Find out about these steps in detail and write them down in your words.

Types of Respiration

There are two types of respiration:

  1. Aerobic Respiration - It is a sort of energy-producing cellular respiration that occurs when there is oxygen present.

  2. Anaerobic Respiration - It is a sort of cellular respiration that generates energy in the absence of oxygen.


Phases of Respiration

In prokaryotic cells, respiration takes place along the plasma membrane and in the cytosol. The mitochondria, commonly known as the cell's powerhouse, is where respiration occurs in eukaryotic cells. There are three phases of respiration:

  1. Glycolysis

  2. Oxidative Phosphorylation

  3. Citric Acid Cycle


Oxygen and Respiration

As much as 97% oxygen is transported by RBC in blood while the rest gets dissolved in plasma. Hemoglobin irreversibly mixes with oxygen to form oxyhaemoglobin; it is entirely dependent on the pressure of oxygen, carbon dioxide, temperature, and concentration of H+.

The alveoli offer an ideal condition for the formation of oxyhaemoglobin. On the other hand, the tissues tend to harbour contrasting conditions which leads to dissociation of oxygen from the oxyhaemoglobin. On average, every 100 ml of oxygenated blood can deliver around 5ml of oxygen to tissues.

Carbon Dioxide and Respiration

Around 20-25% of carbon dioxide is transported through RBCs, and 70% is transmitted as bicarbonate. Notably, around 7% of dissolved carbon dioxide is transported through plasma.

Carbon dioxide gets bound with haemoglobin with the help of the partial pressure exerted by carbon dioxide and oxygen. As the concentration of carbon dioxide is high in the tissues, the process of binding carbon dioxide occurs automatically.

Next, the enzyme, carbonic anhydrase facilitates the reaction, wherein the carbon dioxide dissociates from carbamino-hemoglobin. As a result, the bicarbonates formed in tissues release carbon dioxide in the alveoli. Every 100 ml of deoxygenated blood delivers around 4ml of carbon dioxide to the alveoli.

Respiratory System Disorder

The mechanism of respiration is quite important in the human body, owing to the array of reactions it imitates and facilitates. However, often the respiratory system is subjected to some pathogenic conditions.

These following are some common respiratory diseases which bother human beings.

  1. Asthma.

  2. Emphysema.

  3. Pneumonia.

  4. Chronic bronchitis.

  5. Cystic fibrosis.

Find out more about the transport of oxygen and carbon dioxide in the respiratory system and respiratory disorders in detail straight from subject experts. Join our live online classes to get your doubts cleared from our faculties and improve your knowledge on these topics.

Transport of Oxygen and Carbon Dioxide through Respiration - At A Glance

1. Oxygen Transport: Oxygen is primarily transported through the blood by erythrocytes which contain a metalloprotein called haemoglobin, composed of four subunits with a ring-like structure containing one atom of iron bound to a molecule of heme. Heme binds oxygen such that each hemoglobin molecule is able to bind up to four oxygen molecules. Saturated hemoglobin is when all of the heme units in the blood are bound to oxygen and when only some heme units are bound to oxygen, hemoglobin is said to be partially saturated.

Oxygen–hemoglobin saturation/dissociation curve is a common way to depict the relationship of how easily oxygen binds to hemoglobin or dissociates from hemoglobin with respect to the partial pressure of oxygen. With the increase in partial pressure of oxygen, the hemoglobin binds more readily to oxygen. Also, once one molecule of oxygen binds to hemoglobin, binding of other molecules of oxygen to hemoglobin becomes easier. Other factors such as pH, temperature, the concentration of 2,3-bisphosphoglycerate, and the partial pressure of carbon dioxide can increase or inhibit the binding of hemoglobin to oxygen. The structure of the hemoglobin of the foetus is different from the adult hemoglobin, because of which foetal hemoglobin has a greater affinity for oxygen than adult hemoglobin.

2. Carbon Dioxide Transport: Carbon dioxide can be transported in the blood by any of the three different mechanisms, which are in the form of bicarbonate, or as carbaminohemoglobin or simply in dissolved carbon dioxide form in the blood. The carbon dioxide is transported for exhalation largely in the form of bicarbonate which is formed in erythrocytes. Bicarbonates ions are formed by the dissociation of carbonic acid which is formed by the combination of carbon dioxide with water in the presence of an enzyme called carbonic anhydrase. As the bicarbonate level rises in erythrocytes, it is exchanged with the chloride ions by passing through the membrane into the plasma by a mechanism known as chloride shift. Bicarbonate re-enters erythrocytes in exchange for chloride ions in the pulmonary capillaries, reversing the reaction with carbonic anhydrase, thereby forming carbon dioxide and water. The carbon dioxide diffuses out of the erythrocyte into the air through the respiratory membrane.


Respiration in Vertebrates

The gills and lungs are the principal respiratory organs of vertebrates even though sometimes skin is also used for respiration.


The most common type of respiration in protochordate is external cutaneous respiration. When breathing externally, gas exchange takes place at the skin's surface, allowing oxygen and carbon dioxide to enter and exit tissues.

Frogs meet roughly half of their needs for gas exchange through their skin, and the process still occurs in small vertebrates as long as they have low activity levels and live in cold, flowing water or in the damp air.


Numerous creatures have evolved specialised organ systems to carry out the process of diffusion because the majority of vertebrates are too large for each cell to interact with the environment directly.


Ventilation of Respiratory Organs

Gaseous exchange can take place by ventilation of the respiratory system's organs.


Tetrapods utilise their lungs and fish use their gills for respiration. Respiratory system ventilation is dependent on:

  1. Ram Ventilation

  2. Dual Pump

  3. Pulse Pump

  4. Aspiration Pump


1. Ram ventilation: A fish can also breathe more simply by swimming forward while keeping its mouth open and allowing water to pass over its gills, which is called Ram ventilation. In Ram ventilation, water movement over the gill membranes is aided by forwarding velocity. It has a disadvantage that the fish must swim continuously in order to continue breathing.


2. Dual Pump: The enlargement of the buccal and opercular cavities when the opercula are closed causes water to be pulled into the buccal cavity through the mouth. The water is then forced across the gills and out the opercula when the mouth and oral valve close, the opercular valve opens, and the buccal and opercular cavities contract. Due to the fact that the respiratory pump operates in two phases, it is occasionally referred to as the dual pump.


3. Pulse Pump: The dual pump is modified into an inhalation/exhalation phase. The exhalation phase begins with the transfer of spent air from the lungs into the buccal cavity. The exhalation phase concludes with the expulsion of air from the buccal cavity to the outside through the mouth or under the operculum. The inhalation phase starts with the organism taking fresh air into the mouth.


4. Aspiration Pump: Since the lungs are inside the pump, the force needed to ventilate them is applied directly. Low pressure that is formed around the lungs causes air to be aspirated. Instead of the buccal cavity's action, pressure changes are brought on by the diaphragm and rib cage.


Respiratory Organs of Vertebrates

The necessity for oxygen influences the structure of the respiratory system. The majority of vertebrates have thin-walled, well-blood-supplied structures for their external respiratory organs. The lungs, integumentary exchange regions, and gills are among the three main types of respiratory organs in vertebrates.


1. Gills

In vertebrates, gills are of two types, internal and external.


  1. Internal Gills: The internal gills of the majority of vertebrates are made up of filamentous leaflets that are protected by bony plates (as in fish).


Fish have one of three main morphologies for their gills:

  • Holobranch: Holobranch refers to a whole gill. It is made up of cartilaginous or bony arches (jawed fishes).

  • Hemibranch: Half of a typical gill or a gill with a single series of filaments is a hemibranch gill commonly seen in sharks.

  • Psuedobranch gills: A modified gill bar with posterior filaments for a purpose other than breathing, such as sensing or salt balance are psuedobranch gills. These are found in Rays and Skates.


  1. External Gills: In a few species, the gills are completely exterior (as in Necturus, a neotenic salamander). The majority of them are seen in larval or paedomorphic amphibians, which grow from the skin ectoderm of the branchial area but are not directly associated with the visceral skeleton or branchial chambers.


2. Swim Bladders

Swim bladders are comparable to lungs, but they are only found in fish that inhabit oxygen-rich environments; as a result, the air-filled spaces serve more as a hydrostatic organ.


3. Lungs and Their Ducts

Tetrapod lungs are two paired organs that are enclosed in the pleural cavity and encircled by pleura. Compared to the gills, they have a larger surface-to-area volume ratio. During respiration, air enters through the mouth or the external nares to the choanae, travels through the pharynx, and then passes through the glottis to the trachea. The trachea then divides into bronchi, which lead to the lungs, which are highly lobed structures. Branching continues from the bronchi into bronchioles, then alveolar sacs, and finally ends in alveoli, a small sac where gas exchange takes place within the lung.


Numerous changes to the respiratory structures occurred during the development of the lungs from amphibians to mammals, with ventilation of the lungs being the primary focus of these changes. Air is pulled into the pharynx by muscle contraction that lowers the pharynx floor in amphibians; this prevents the lungs from being ventilated through the mouth.


In reptiles, contraction of the diaphragmatic muscle, which is not the same as the diaphragm, aids in the muscle movement against the ribs that changes internal air pressure and causes inspiration. The size of a bird's lungs is half that of a similarly-sized mammal's lungs.


What is the Respiratory System?

The network of organs and tissues that makes up the human respiratory system aids in breathing. This system's main job is to get more oxygen into the body and get more carbon dioxide out of it.


The human respiratory system is comprised of a group of organs and tissues that aids in breathing. In addition to the lungs, the respiration process is aided by muscles and a complex network of blood arteries.


Respiratory Tract

The human respiratory tract consists of the following components:

  • External Nostrils: Air intake occurs through the external nostrils.

  • Nasal Chamber: Hair and mucus line the nasal chamber, which serves as a filter for dust and other particles.

  • Pharynx: It is a passage located behind the nasal cavity, and is the body's primary pathway for both food and air.

  • Larynx: The vocal cords, which are crucial for producing sound, are housed in the larynx, which is also referred to as the "soundbox."

  • Epiglottis: The epiglottis is a structure that resembles a flap and covers the glottis to keep food from entering the windpipe.

  • Trachea: A lengthy tube called the trachea travels across the mid-thoracic cavity.

  • Bronchi: The trachea gets separated into left and right bronchi.

  • Bronchioles: Each bronchus is further segmented into smaller tubes called bronchioles.

  • Alveoli: The balloon-like structures known as alveoli are where the bronchioles end.

  • Lungs: Humans have two lungs, which are sac-like organs encased in a two-layered membrane called the pleura.


Human Respiratory System


Human Respiratory System


Process of Respiration in Humans

With the aid of the nostrils, the air is inhaled, and the tiny hair follicles inside them clean the air in the nasal cavity. A collection of blood vessels that warm the air is also present in the hollow. This air then travels through the pharynx, larynx, and trachea.


Goblet cells (secretory cells) and ciliated epithelial cells line the trachea and bronchi, releasing mucus to moisten the air as it travels through the respiratory tract. Additionally, it stops any tiny dust particles or pathogens from entering the nasal passages. The rising action of the motile cilia transports the mucus and other foreign particles back to the buccal cavity, where they are removed. The ascending motion of the motile cilia causes the mucus and other foreign particles to be taken back to the buccal cavity, where they can either be coughed out or expelled (or swallowed.)


The bronchioles and alveoli are the next places the air goes after entering the bronchus.


Mechanism of Breathing

  1. Inspiration: Due to the lower intrapulmonary pressure, atmospheric air is drawn inside. The diaphragm and intercostal muscles contract, resulting in an increase in lung volume. The air enters the lungs when the sternum and ribs rise.

  2. Expiration: Alveolar air is spat out because the intrapulmonary pressure is higher than the ambient pressure during expiration. When the diaphragm and intercostal muscles relax, the pressure rises. The diaphragm, sternum, and ribs all come back to their original locations. The abdominal muscles can aid in increasing the volume of inhalation and expiration. The average person breathes 12–16 times each minute. A spirometer is a device for measuring the amount of air breathed in and exhaled.

  3. Exchange of gases: The exchange of gases occurs across a gradient in pressure and concentration. Between blood and tissues as well as between alveoli, there is gas exchange.

  4. Oxygen transport: The blood carries O2 throughout the body. RBCs carry 97% of the oxygen, while 3% of it is dissolved in plasma.

  5. Carbon dioxide transport: The production of carbaminohemoglobin allows for the transportation of CO2 via the blood. This method of transporting CO2 involves 20–25 percent of it, 70 percent of it as bicarbonate, and 7 percent of it as plasma-dissolved CO2.


The Function of the Respiratory System

The human respiratory system serves the following purposes:

  1. Inhalation and Exhalation: Breathing is aided by the respiratory system (also known as pulmonary ventilation.) The pharynx, larynx, trachea, and lungs all pass the air that is inhaled through the nose. Through the same channel, the exhaled air is returned. Pulmonary ventilation is aided by changes in the volume and pressure of the lungs. Gases are exchanged between the bloodstream and the lungs.

  2. Exchange of Gases between Lungs and Bloodstream: Millions of tiny sacs called alveoli allow oxygen and carbon dioxide to enter and leave the lungs, respectively. When oxygen is inhaled, it diffuses into pulmonary capillaries, binds to haemoglobin, and then moves through the bloodstream. The blood's carbon dioxide diffuses into the alveoli and is released during breathing.

  3. Exchange of Gases between Bloodstream and Body Tissues: When it reaches the capillaries, the blood releases the oxygen that it has been carrying around the body since it left the lungs. The bodily tissues receive oxygen diffusion through the capillary walls. Additionally, the carbon dioxide diffuses into the circulation, where it is then transported to the lungs for exhalation.

  4. The Vibration of the Vocal Cords: The arytenoid cartilage is moved by the laryngeal muscles while speaking. The vocal cords are pushed together by these cartilages. The air that is exhaled causes the vocal cords to vibrate and produce sound when it passes through them.

  5. Olfaction: Some substances in the air bind to nasal cavities when it enters the nasal canals during breathing, activating the cilia's nervous system receptors. The brain transmits the impulses to the olfactory bulbs.


Interesting Facts

  • The only organs that can float on water are the lungs. Alveoli, which resemble small balloons, are found in each of your lungs and are responsible for replacing the carbon dioxide waste in your blood with oxygen.

  • 70% of the waste gases like carbon di oxide is expelled when you breathe.

  • The alveoli are tiny air sacs located in the lungs where gas exchange takes place. The adult lungs contain between 300 million and 500 million alveoli.


Summary

All living things use respiration to supply and release energy by transforming food energy into chemical forms that can be used for metabolism. Energy is released in a controlled, step-by-step way by the process, allowing it to be properly utilised for all cellular functions like metabolism and cell division. Numerous chemical molecules that are used in cellular metabolism are created from a variety of intermediate products of the citric acid cycle and glycolysis.


In plants, the oxygen needed for respiration is refilled with the oxygen supplied during photosynthesis, and the carbon dioxide needed for photosynthesis is replenished by the carbon dioxide emitted during respiration. As a result, photosynthesis and respiration work in unison to keep the natural environment's carbon dioxide and oxygen levels balanced. This article helps to understand the process of respiration in detail. It has provided all the information regarding respiration and gaseous exchange.

Last updated date: 28th Sep 2023
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FAQs on Transport of Oxygen and Carbon Dioxide through Respiration

1. What is respiration?

It is a process through which human beings breathe in oxygen and release carbon dioxide. Since it is a catabolic process, it helps to convert food into small molecules to release energy. Respiration is a physical and chemical process through which an organism provides oxygen to its cells and tissues so that it can carry out the process of metabolism. Therefore, it is a process that occurs in living organisms for the production of energy. Through this process, cells and tissue liberate their carbon dioxide through an energy-producing reaction.

2. How carbon dioxide is carried in the blood?

Carbon dioxide can be transported to the lungs through blood in three different ways, that is, it might get transported by simply dissolving in the blood or it can be buffered with water in the form of carbonic acid or it can bind to haemoglobin protein and get transported. Though a significant part of carbon dioxide is transported as carbamino-haemoglobin, a large portion is transported in the form of bicarbonate. Also, a small portion of carbon dioxide gets dissolved in plasma.

3. What are the major respiratory organs?

Respiratory organs are those organs that are part of the respiratory tract of a human being. These respiratory organs play a vital role in the process of respiration and perform all the functions associated with respiration. Each respiratory organ has a definite role to play in the process of respiration and without them, people can suffer from some major health issues. These are the major respiratory organs in human beings including the nose, larynx, pharynx, bronchi, trachea and lungs. Together they facilitate the transport of oxygen and carbon dioxide and facilitate the energy reaction in the body.

4. What will be the outcome of studying the transport of oxygen and carbon dioxide through respiration?

By studying the transport of Oxygen and Carbon Dioxide through Respiration, students will be able to :

  • Analyse the relationship between the amount of oxygen dissolved in the blood and the partial pressure of oxygen in the blood.

  • Chemically analyse the combination of oxygen with haemoglobin.

  • Efficiently study the oxyhemoglobin dissociation curve

  • Define terms like haemoglobin saturation, the oxygen content of blood, and oxygen-carrying capacity related to the transport of oxygen.

  • Analyse the effect of the shape of the oxyhemoglobin dissociation curve.

  • Enlist physiological factors that can affect the shape of the oxyhemoglobin dissociation curve.

  • Study the relation of partial pressure of carbon dioxide with the amount of carbon dioxide physically dissolved in the blood.

  • Explain the transport of carbon dioxide in the form of carbamino compounds with blood proteins.

  • Describe Bohr's effect and Haldane effect.

  • Explain the carbon dioxide dissociation curve

  • Explain the process of transportation of carbon dioxide as bicarbonate.

5. What is meant by oxygen cascade in oxygen transport?

Oxygen cascade refers to the movement of oxygen down the concentration gradient from a region of relatively high level, that is, air to the region of relatively low level, that is, the cell. Mitochondria has the lowest level of partial pressure of oxygen, which is 4 - 20 mm Hg. The major steps involved in oxygen cascade are uptake of oxygen in the lungs, transport of oxygen by the blood on the basis of its carrying capacity, delivery of oxygen to capillaries, interstitium and then to individual cells where it is used for various cellular processes.


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