General Science Questions (MCQs) for Competitive Examinations

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A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids. It refers to the use of wood tannins from oak in tanning animal hides into leather.

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Eutrophication is the ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage. It leads not only to increased levels of nutrients, but increased Biological Oxygen Demand as well following the decay of algal bloom in stagnant water reservoirs.

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Fructose, or fruit sugar, is a simple ketonic monosaccharide found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is a 6-carbon polyhydroxyketone with chemical formula of C6H12O6.

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The constituents of phloem are Sieve tubes, Companion cells, Phloem parenchyma, Phloem fibres. Tracheids are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts. These are elongated narrow tube like cells with hard thick and lignified walls with large cell cavity.

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In algae, sexual reproduction takes place through fusion of two gametes. It is of two types on the basis of the size of gametes : isogamous (where male and female gametes are morphologically similar) and heterogamous (anisogamous and oogamous). Anisogamous fusion happens when gametes are dissimilar in size.

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Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects. It is usually produced in the skin of human and animals under the influence of solar or ultraviolet radiation. In plants it can be produced from provitamin ergosterol.

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Chloramines are a group of chemical compounds that contain chlorine and ammonia. It is used as a disinfectant for water. The particular type of chloramine used in drinking water disinfection is called monochloramine. However, it is used as a secondary disinfectant that are added to water that has already been disinfected with a primary disinfectant, often chlorine using bleaching powder.

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Amino acids are the molecular building blocks of proteins. So proteins are synthesized from them. Essential amino acids are histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, valine, lysine.

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The inner walls of the small intestine have thousands of finger-like outgrowths called villi (singular villus). The villi increases the absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The surface of the villi absorbs the digested food materials.

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Xerophthalmia caused by a severe vitamin A deficiency is described by pathologic dryness of the conjunctiva and cornea. The conjunctiva becomes dry, thick and wrinkled. Since retinoic acid cannot be reduced to retinal or retinol, these effects on the cornea must be specific to retinoic acid. Scurvy happens when there is a lack of vitamin C, or ascorbic acid. Hemorrhagic disease is caused due to the deficiency of Vitamin K. Rickets is caused due to the deficiency of Vitamin D.