NEET Practice Questions (MCQs) with Answers & Solutions

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.

Dead space refers to areas of the respiratory system where no gas exchange occurs. The upper respiratory tract, including the nose, pharynx, and trachea, is considered dead space because it only conducts air to the lungs but does not participate in gas exchange.

• Upper respiratory tract: Includes nasal passages, pharynx, and larynx.
• Lower respiratory tract: Includes the trachea, bronchi, and lungs, where the alveolar spaces are situated.

Carbon dioxide in tobacco smoke can bind to hemoglobin more readily than oxygen, forming carboxyhemoglobin. This reduces the oxygen-carrying capacity of the blood, leading to decreased oxygen supply to tissues.

• Carboxyhemoglobin: Formed when carbon dioxide binds irreversibly to hemoglobin, reducing its ability to carry oxygen.
• Effects: Can cause hypoxia and decrease overall oxygen delivery to the body's tissues.

Pulmonary ventilation refers to the total volume of air moved into and out of the respiratory system per minute. Alveolar ventilation is the volume of air that reaches the alveoli and is available for gas exchange per minute. Because some of the air remains in the conducting airways (anatomical dead space) and does not participate in gas exchange, alveolar ventilation is always less than pulmonary ventilation.

An increase in CO₂ concentration in the blood leads to a condition known as hypercapnia. The body responds to hypercapnia by increasing the rate and depth of breathing (faster and deeper breathing) to expel more CO₂ and bring the levels back to normal. This response is mediated by chemoreceptors that sense the elevated CO₂ levels and stimulate the respiratory centers in the brain.

SARS (Severe Acute Respiratory Syndrome) is caused by a coronavirus, specifically the SARS-CoV virus. The coronavirus family also includes viruses that cause the common cold, but SARS is caused by a different, more severe variant. It is important to distinguish between different diseases caused by coronaviruses.