General Science Questions (MCQs) for Competitive Examinations

Notes:
The melting point of a pure substance is always higher than the melting point of that substance when a small amount of an impurity is present. Melting point decreases with increase of impurity in water. Increase in impurity increases the electrostatic attraction between ions and thus more energy is needed to break the bonds. The surface tension of water increases when highly soluble impurities are added to it.

Notes:
Heavy water is water that contains heavy hydrogen or deuterium. Deuterium differs from the hydrogen usually found in water, protium, in that each atom of deuterium contains a proton and a neutron. Heavy water may be deuterium oxide, D2O or it may be deuterium protium oxide, DHO.

Notes:
Leptospirosis is a bacterial disease caused by corkscrew-shaped bacteria called Leptospira. Signs and symptoms can range from none to mild such as headaches, muscle pains, and fevers; to severe with bleeding from the lungs or meningitis. If the infection causes the person to turn yellow, have kidney failure and bleeding, it is then known as Weil’s disease.

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Typhoid fever, also known as typhoid, is a common water borne worldwide bacterial disease, transmitted by the ingestion of food or water contaminated with the feces of an infected person, which contain the bacterium Salmonella Typhi.

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Composting is the depomposition of plant remains and other once-living materials to make an earthy, dark, crumbly substance that is excellent for enriching soil. It is the chief way to recycle wastes.

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Veins carry the deoxygenated blood from different parts of the body to the heart. There are two main veins that carry out this job. The superior vena cava carries deoxygenated blood from head, neck, thorax and hands to the right atrium of our heart. The inferior vena cava carries deoxygenated blood from legs, pelvic region and abdominal organs to the right atrium of our heart. Among the veins, only pulmonary vein carries oxygenated blood.

Notes:
Bacillus Calmette–Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis. The vaccine was originally developed from Mycobacterium bovis which is commonly found in cows. It is on the World Health Organization’s List of Essential Medicines, the most effective and safe medicines needed in a health system.

Notes:
Animals that have a cavity between body wall and digestive tract are known as coelomates for e.g.. annelids, molluscs, arthropods, Echinodermata, and chordates etc. In contrast, animals in which the body cavity is absent are known as acoelomates. Platyhelminthes is an example of acoelomates. The presence or absence of body cavity or coelom plays a very important role in the classification of animals.

Notes:
Protein digestion begins in the stomach with the action of pepsin. Pepsin is the active protein-digesting enzyme of the stomach. When pepsin acts on the protein molecule, it breaks the bonds that hold the protein molecule together, called peptide bonds. Once broken, peptide bonds yield chains of amino acids linked together called polypeptides that are further digested in the small intestine with the help of trypsin, chymotrypsin, and carboxypeptidase.

Notes:
Insects and birds have the simplest surface waxes that serve to water proof feathers. The interlocking feather barbs and a special waxy coating create a shield that water runs off of. Besides, while a few components present in surface lipids can prevent growth of pathogens, the total surface with waxed layer certainly functions to prevent microbial entry into the organism.