Respiration: Transport Of Oxygen And Carbon Dioxide

What Is Respiration?

Respiration is the process through which living organisms use food to produce energy biologically. It is the means of transporting respiratory gases-oxygen and carbon dioxide-between the organism and the environment through a two-way exchange. It is significant for sustaining life as the cells receive oxygen for their functions and remove the metabolic by-product, carbon dioxide, from the body.

Oxygen and carbon dioxide transport occur through a coordinated system involving the nose, pharynx, larynx, trachea, bronchi, and lungs. This respiratory system allows for efficient gas transport to enable the intake of oxygen and the removal of carbon dioxide for the maintenance of cellular and physiological functions.

Anatomy of the Respiratory System

The respiratory system is responsible for the transport of respiratory gases, including oxygen and carbon dioxide. It consists of the upper and lower respiratory tracts.

The upper respiratory tract includes the nose and pharynx, while the lower respiratory tract comprises the larynx, trachea, bronchi, and lungs. Gas exchange, an essential part of the transport of gases, occurs within the alveoli, the small air sacs in the lungs.

Mechanisms of Breathing

Respiration refers to the exchange and transport of oxygen and carbon dioxide between the atmosphere and the body. Breathing, an integral part of gas transport, involves inspiration and expiration. This process is facilitated by pressure changes in the thoracic cavity caused by the contractions of the diaphragm and intercostal muscles, ensuring efficient transport of oxygen and carbon dioxide.

Inhalation

In the transport of respiratory gases, inhalation takes place when the diaphragm contracts, increasing the volume of the thoracic cavity and allowing air to rush into the lungs.

Exhalation

The exhalation process takes place when the diaphragm relaxes, reducing the volume of the thoracic cavity and forcing air out of the lungs.

Transport of Oxygen

Respiration deals with the transport of gases, such as oxygen and carbon dioxide. Oxygen is carried from the lungs to tissues by the bloodstream, whereas carbon dioxide, the waste product, is carried back to the lungs for excretion.

Role of Haemoglobin

Haemoglobin, the most important protein of red blood cells, enables oxygen transport. In the lungs, haemoglobin combines with oxygen to form oxyhemoglobin. This complex circulates in the bloodstream and gives up oxygen in tissues where its partial pressure is low.

Oxyhemoglobin Dissociation Curve

The oxyhemoglobin dissociation curve is the relation that exists between oxygen saturation and partial pressure of oxygen. It shows how haemoglobin binds and releases oxygen under various conditions of physiological importance for a means of effective gas transport.

Transportation of Carbon Dioxide

Carbon dioxide is a metabolic waste that is transported from tissues to the lungs for exhalation through the following three major mechanisms: dissolved in plasma, as bicarbonate ions, and bound with haemoglobin.

Three Forms of CO₂ Transport

• Dissolved in Plasma: A small amount of carbon dioxide dissolves directly in the blood plasma.

• Bicarbonate Ions: With the aid of carbonic anhydrase, most carbon dioxide is changed to bicarbonate ions.

• Carbamino Hemoglobin: Carbon dioxide combines with haemoglobin to form carbaminohemoglobin.

Structure and Function of Alveoli

The alveoli are tiny, balloon-like structures that have very thin walls and enable the transport of oxygen and carbon dioxide. These alveoli lie adjacent to capillaries so that these gases exchange readily by diffusion across the membrane.

Regulation of Respiration

The regulation of respiration occurs by two main mechanisms:

Brainstem Control

The medulla oblongata and pons control breathing in the brainstem through the monitoring of oxygen and carbon dioxide levels. This adjusts the depth and rate of respiration to ensure efficient gas transport.

Role of Chemoreceptors

Chemoreceptors in the carotid and aortic bodies monitor changes in the amount of oxygen and carbon dioxide in the blood. Chemoreceptors send signals to the brain, which modulates respiration to ensure that there is efficient gas transport.

Cellular Respiration

Cellular respiration is the biological process through which cells obtain energy. During this process, glucose is broken down, producing carbon dioxide, water, and ATP, thereby supporting the body's metabolic needs.

Respiration NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Transport of Oxygen

• Regulation of respiration

Practice Questions for NEET

Q1. The carbon dioxide that enters the RBCs forms a reversible compound with an amino group NH2 of the globin part of hemoglobin. This compound is called

1. Carbaminohemoglobin

2. Oxyhaemoglobin

3. Carboxyhaemoglobin

4. Carbaminohemoglobin

Correct answer: 1) Carbaminohemoglobin

Explanation:

The carbon dioxide that enters the RBCs forms a reversible compound with an amino group NH2 of the globin part of hemoglobin. The compound so formed is called carbaminohemoglobin.

Hence, the correct answer is option 1) Carbaminohemoglobin.

Q2. In the RBC, the formation of carbonic acid is due to the presence of a zinc enzyme called

1. Carbaminase

2. Carbonic oxidase

3. Carbonic decarboxylase

4. Carbonic anhydrase

Correct answer: 4) Carbonic anhydrase

Explanation:

Nearly 20-25 percent of CO2 is transported by RBCs:

• The carbon dioxide that enters the RBCs forms a reversible compound with an amino group (NH2) of the globin part of haemoglobin.

• The compound so formed is called carbaminohemoglobin.

In the RBC, the formation of carbonic acid is due to the presence of a zinc enzyme called carbonic anhydrase.

Hence, the correct option is 4) Carbonic anhydrase.

Q3. At high temperatures, the Hb will be less likely to stick to the oxygen and release it into the tissues, this causes the oxygen dissociation curve to shift to

1. Left

2. Right

3. No movement

4. Slightly left then right

Correct answer: 2) Right

Explanation:

DPG (2,3-diphosphoglycerate) and temperature both shift the oxygen dissociation curve to the right, promoting oxygen release from haemoglobin to tissues. DPG binds to haemoglobin, reducing its affinity for oxygen, especially at lower oxygen concentrations. Increased temperature also decreases haemoglobin's affinity for oxygen, enhancing oxygen delivery during conditions like exercise or fever. These changes help tissues receive more oxygen when metabolic demand is high.

At high temperatures, the Hb will be less likely to stick to the oxygen and release it into the tissues. The curve shifts to the right when the temperature increases.

Hence, the correct answer is option 2) Right.

Also Read:

• MCQs on Transport of Carbon dioxide

• Breathing and Exchange of Gases

• Lung Volumes and Lung Capacity

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