Breathing and Exchange of Gases MCQs for NEET — Zoology Questions with Answers

At high altitudes, the oxygen levels are lower. To compensate for the reduced oxygen availability, the body increases the number of red blood cells (RBCs) to enhance the oxygen-carrying capacity of the blood. This process is called erythropoiesis and is stimulated by the hormone erythropoietin.

The maximum amount (70-75%) of carbon dioxide is transported in the blood in the form of bicarbonate ions (HCO3-). When CO2 enters the red blood cells, it reacts with water to form carbonic acid (H2CO3), which quickly dissociates into bicarbonate and hydrogen ions. This reaction is catalyzed by the enzyme carbonic anhydrase.

Oxygen is primarily transported in the blood bound to hemoglobin in red blood cells (RBCs). Carbon dioxide is transported in the blood in three forms: dissolved in plasma, as bicarbonate ions, and bound to hemoglobin (carbaminohemoglobin). Therefore, both oxygen and carbon dioxide are transported through RBCs and plasma.

Tidal volume is the amount of air that is inhaled or exhaled during normal, relaxed breathing. It has the lowest value compared to other respiratory volumes like vital capacity, inspiratory reserve volume, and expiratory reserve volume. Vital capacity is the maximum amount of air a person can expel from the lungs after a maximum inhalation, and both inspiratory and expiratory reserve volumes are additional volumes of air that can be inhaled or exhaled beyond the normal tidal volume.

A molecule of hemoglobin can carry up to 4 oxygen molecules. Hemoglobin has four subunits, each containing an iron atom that can bind to one molecule of oxygen. Thus, one hemoglobin molecule can transport four oxygen molecules.

Haemoglobin is a respiratory pigment found in red blood cells. It binds to oxygen in the lungs and transports it to tissues throughout the body. This is essential for cellular respiration, where oxygen is used to produce energy.

The vocal cords are located in the larynx, commonly known as the voice box. They vibrate to produce sound when air passes through them during exhalation, enabling speech and other vocalizations.

Hiccoughs or hiccups are caused by involuntary contractions of the diaphragm. This sudden contraction causes the glottis to close briefly, producing the characteristic 'hic' sound.

The thoracic cage, also known as the rib cage, is formed by the ribs, sternum, and thoracic vertebrae. These structures together protect vital organs such as the heart and lungs.

• Ribs: 12 pairs of ribs, each connected to the thoracic vertebrae at the back.
• Sternum: The flat bone located at the front center of the chest.
• Thoracic vertebrae: The 12 vertebrae of the spine to which the ribs are attached.