General Science

Carbon monoxide (CO) is highly toxic because it binds to hemoglobin with approximately 240 times greater affinity than oxygen. This forms carboxyhemoglobin, reducing the blood's oxygen-carrying capacity and causing tissue hypoxia. CO does not react quickly with UV radiation (B), nor does it cause ozone depletion (D). Option C is factually opposite to the truth.

Monocytes are the largest white blood cells (corpuscles) in human blood, measuring 12-20 micrometers in diameter. They are part of the immune system and can differentiate into macrophages or dendritic cells. Basophils and acidophils (eosinophils) are smaller granulocytes, while lymphocytes are also smaller than monocytes.

In open circulatory systems (found in arthropods and mollusks), the circulating fluid is called hemolymph, which is analogous to blood in closed systems. Hemolymph directly bathes the tissues in body cavities called sinuses. Blood (D) is specific to closed circulatory systems. Perilymph relates to the inner ear, and lymphatic fluid is part of the lymphatic system.

Adrenaline (epinephrine) directly stimulates the sinoatrial (SA) node, the heart's natural pacemaker, increasing heart rate and contractility. This is part of the 'fight or flight' response. It does not directly affect the islets of Langerhans (pancreatic hormone-producing cells), oxyntic cells (stomach acid-producing), or dorsal root ganglia (sensory nerve clusters).

Hirudin is the specific anticoagulant produced by the salivary glands of medicinal leeches (Hirudo medicinalis). It prevents blood clotting during feeding by inhibiting thrombin. Heparin is produced by mast cells in mammals, sodium citrate is an inorganic anticoagulant used in blood storage, and chelating agents are a broader category of compounds that bind metal ions.

Pulse pressure is the arithmetic difference between systolic pressure (peak pressure during heart contraction) and diastolic pressure (minimum pressure between beats). Normal pulse pressure is typically 30-50 mmHg. It reflects the force generated by the heart and arterial elasticity. Options A, B, and C describe individual components but not the definition of pulse pressure itself.

At high altitudes, decreased atmospheric oxygen partial pressure triggers increased erythropoietin production, which stimulates red blood cell (RBC) production in bone marrow. This adaptive response, called polycythemia, improves oxygen-carrying capacity. The RBC count increases, not the size. Options C and D are incorrect as RBC count increases, not decreases. Size changes are not the primary adaptation.

William Harvey published 'De Motu Cordis' in 1628, establishing that blood circulates through the body pumped by the heart, overturning the Galenic view that the liver was the central organ of circulation. Harvey demonstrated through experiments that blood flows in a continuous loop through arteries and veins.

Oxyhaemoglobin releases oxygen in tissues because tissue cells are constantly consuming oxygen for cellular respiration, creating a low partial pressure environment (low pO2) that favors dissociation. This oxygen delivery mechanism is essential for supplying oxygen to metabolically active tissues.

Pulmonary veins are the only veins in the body that carry oxygenated blood, transporting it from the lungs back to the left atrium of the heart. This oxygen-rich blood is then pumped to the rest of the body through the systemic circulation.

Blood group antigens (A, B, Rh factors) are glycoproteins or glycolipids on RBC surfaces determined by specific genes. These antigens are inherited from parents and form the basis for blood type classification, making them the hereditary factors present on RBC membranes.

Erythroblastosis foetalis occurs when an Rh-negative mother is sensitized to Rh-positive fetal red blood cells, usually during delivery, and subsequently produces anti-Rh antibodies. These IgG antibodies can cross the placenta in a subsequent Rh-positive pregnancy and destroy fetal RBCs.

Purkinje fibres are specialized cardiac muscle fibers located in the ventricles that form the terminal part of the conduction system. They rapidly transmit electrical impulses from the AV bundle to the ventricular myocardium, ensuring coordinated ventricular contraction.

Diamond is pure crystalline carbon (element C), making it an element. Ruby (Al2O3 with Cr), Sapphire (Al2O3 with Ti/Fe), and Emerald (Be3Al2Si6O18 with Cr) are all minerals containing multiple elements, not single elements.

Wood charcoal's highly porous structure provides enormous surface area for adsorption, making it an effective decolorizing agent in sugar refining. It absorbs colored impurities without chemically reacting with the sugar itself, primarily through physical adsorption on its extensive internal surface.

Galvanisation is the process of applying a protective zinc coating to iron or steel to prevent rusting. Zinc acts as a sacrificial anode, oxidizing preferentially to iron, and also forms a protective layer of zinc carbonate that prevents atmospheric corrosion.

Protium (¹H), Deuterium (²H or D), and Tritium (³H or T) are the three isotopes of hydrogen, differing only in neutron count. Yttrium (Y) is a separate transition metal element (atomic number 39) in Group 3 of the periodic table, not related to hydrogen.

Carborundum is the trade name for silicon carbide (SiC), an extremely hard synthetic abrasive material. Silicon carbide consists of covalently bonded silicon and carbon atoms in a tetrahedral structure, giving it exceptional hardness and thermal conductivity, making it valuable for abrasive and cutting applications.

Silver halides (specifically silver bromide and silver chloride) are light-sensitive compounds used in photographic films. When exposed to light, they undergo reduction to form metallic silver, creating the latent image that is later developed.

Zeolites are aluminosilicate minerals that can exchange sodium ions for calcium and magnesium ions. This ion exchange process effectively removes permanent hardness caused by metal sulfates from water.

Graphite has a layered structure where weak van der Waals forces exist between layers. This allows layers to slide over each other easily, making graphite an excellent solid lubricant.

Allotropes are different physical forms of the same element that have identical chemical properties but different physical properties due to variations in atomic arrangement. Diamond and graphite are well-known allotropes of carbon.

According to Newton's third law, when the horse pushes backward against the ground, the ground exerts an equal and opposite forward force on the horse. This reaction force is what actually propels the horse forward.

Carbon, diamond, and graphite are all allotropes - different physical forms of the same element (carbon) with identical chemical properties but different physical structures and characteristics.