General Science Questions (MCQs) for Competitive Examinations

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All metal carbonates and hydrogen carbonates react with acids to give a corresponding salt, carbon dioxide and water. Limestone, chalk and marble are different forms of calcium carbonate.

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Antiseptics are applied to the living tissues such as wounds, cuts, ulcers and diseased skin surfaces. Examples of antiseptics are furacine, soframicine, etc

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Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2. 1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another.

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Radon, a radioactive noble gas with atomic number 86, is used in radiotherapy. Created by disintegration of radium, its one of the heaviest gases and a health hazard. Radon gas, chemically inert yet radioactive, can accumulate in buildings and drinking water causing lung cancer. Furthermore, radon is noted for brilliant phosphorescence when cooled below its freezing point. Its most stable isotope, 222Rn, has a half-life of 3.8 days. Groundwater often has a higher 222Rn concentration than surface water due to less exposure to atmosphere.

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Saprophytes are the organisms which depend for food on dead and decaying material. They secrete digestive substances into the surrounding environment and break down the organic matter into simpler substances. The nutrients thus produced are absorbed directly through the cell membranes of the organisms.

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The average adult has a blood volume of roughly 4-5 to 5 litres, which is composed of plasma and several kinds of cells. By volume, the red blood cells constitute about 45% of whole blood, the plasma about 54.3%, and white cells about 0.7%.

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Anaerobic reactions involve break down of glucose into pyruvic acid, which then reacts to produce lactic acid. As muscle metabolism shifts from aerobic to anaerobic ATP production, lactic acid begins to accumulate in muscles and to appear in the bloodstream. This leads to muscle fatigue with changing pH of muscle cells. C6H12O6 —> 2C3H6O3 + 2ATP

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Mycobacterium leprae is a bacillus (rod-shaped) bacterium that causes leprosy, also known as “Hansen’s disease”, which is a chronic infectious disease that damages the peripheral nerves and targets the skin, eyes, and muscles, upper respiratory tract, and nasal mucosa (lining of the nose).

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Cotton is the most popular of the BT crops. In BT cotton, BT gene was isolated and transferred from a bacterium Bacillus thurigiensis to American cotton. The American cotton was subsequently crossed with Indian cotton to introduce the gene into native varieties. The BT cotton variety contains a foreign gene obtained from Bacillus thuringiensis. This bacterial gene, introduced genetically into the cotton seeds, protects the plants from bollworm (A. lepidoptora), a major pest of cotton.

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A tendon or sinew is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments; both are made of collagen. Ligaments join one bone to another bone, while tendons connect muscle to bone.