General Science Questions (MCQs) for Competitive Examinations

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Magnetite (Fe3O4) typically contains about 70% iron by weight. It is black in color and strongly magnetic. Hematite (Fe2O3) contains about 60–70% iron. Limonite contains 35–50% iron. Siderite (FeCO3) contains about 48% iron. Magnetite is widely mined due to its high iron concentration compared to other ores.

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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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Pituitary gland, called Master Gland, is the smallest endocrine gland. It controls the general growth of the body coordinating the functioning of other endo crime glands and stimulates the primary sex hormones, i.e. ovaries and testes.

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Keratin is a family of fibrous structural proteins that is the key structural component of hair and nails. It is also the key structural material making up the outer layer of human skin. Besides, it provides the necessary strength and toughness for masticatory organs, such as the tongue.

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Haemoglobin is called as tetrameric hemoprotein, while myoglobin is called monomeric protein. Haemoglobin is found systematically all over the body, while myo-globin is found in muscles tissues only. The body requires iron for the synthesis of its oxygen transport proteins, in particular hemo-globin and myoglobin.

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The ear has three main parts: the outer, middle and inner ear. The outer ear consists of the pinna and the auditory canal. The middle ear is filled with air and contains three tiny bones called ossicles – the anvil, hammer and stirrup. The inner ear contains the semicircular canals and the cochlea. Eardrum is the membrane of middle ear. Snakes have fully developed inner ear structures but no eardrum.

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Connective tissue is a group of tissues in the body that maintain the form of the body and its organs and provide cohesion and internal support. Bone, ligaments, tendons, cartilage, and adipose (fat) tissue are examples of connective tissue. Cardiac muscle is an example of muscle tissue. It is so named because it is found in the heart.

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Vitamin C is quite unstable when cooked or stored improperly. It is very liable and easily destroyed during cooking as well as storage. It is a water-soluble and temperature-sensitive vitamin, so is easily degraded during cooking, and elevated temperatures and long cooking times have been found to cause particularly severe losses of vitamin C.

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Bile or gall is a bitter-tasting, dark green to yellowish brown fluid, produced by the liver aids in the process of digestion of lipids in the small intestine. In many species, bile is stored in the gall bladder and upon eating is discharged into the duodenum. Bile is a composition of the following materials: water (85%), bile salts (10%), mucus and pigments (3%), fats (1%), inorganic salts (0.7%) and cholesterol (0.3%).

Notes:
Skeletal muscle is a form of striated muscle which is under the voluntary control of the somatic nervous system. Most skeletal muscles are attached to bones by bundles of collagen fibres known as tendons. It is one of three major muscle types, the others being cardiac muscle and smooth muscle.