Defence GK Questions 2026

Iodine is needed to make thyroxine, the hormone of the thyroid gland; when the supply is short the gland works harder and enlarges into the swelling at the front of the neck called goitre, and in an infant the same shortage stunts growth and mental development as cretinism.

Kwashiorkor appears when a child gets enough calories but far too little protein, typically after being weaned onto a starchy gruel; the signs are swelling of the feet and face, a distended belly, thin and discoloured hair and an apathetic look, while the muscles are not severely wasted.

These four dissolve in fat and not in water, so they travel with dietary fat, are stored in the liver and in body fat, show their deficiency only after a long shortage, and can be toxic in excess.

Retinol is vitamin A, and it is the raw material of rhodopsin, the pigment in the rod cells of the retina that lets us see in dim light; when it is short the eye cannot adjust to darkness, which is night blindness, and a longer shortage dries the conjunctiva as…

Vitamin D, chemically calciferol, is needed for the absorption of calcium and phosphorus from the intestine, so a child short of it cannot mineralise growing bone; the legs bow, the wrists thicken and the chest deforms, and the disease is rickets, while the same shortage in an adult softens formed…

Vitamin B12 is chemically cyanocobalamin, and the cobalt atom at the centre of its ring is what the name points to; it is the only vitamin that contains a metal, it is absorbed only with the help of intrinsic factor secreted by the stomach, and its shortage gives pernicious anaemia.

Vitamin B3 is niacin, also called nicotinic acid, and its shortage gives pellagra, remembered by the three Ds of dermatitis, diarrhoea and dementia, with death as a fourth if it is untreated; the disease appeared where maize was the staple, because the niacin in maize is bound and poorly absorbed.

Vitamin K, chemically phylloquinone, is needed by the liver to make prothrombin and other clotting factors, so a shortage of it makes bleeding last longer and can cause haemorrhage in a newborn; green leafy vegetables supply it and the bacteria of the large intestine make part of our requirement.

Thiamine is vitamin B1, and its shortage causes beriberi, in which the nerves and the heart are affected, giving weakness, loss of sensation in the legs and in the wet form swelling and heart failure; the disease was common where polished rice was the staple, since polishing removes the thiamine-rich…

Vitamin C, chemically ascorbic acid, is needed to make collagen, the protein that holds tissues together; without it the gums swell and bleed, wounds refuse to heal and the joints ache, and the disease is called scurvy.

Amylase breaks starch into the sugar maltose; a lipase works on fat, and saliva carries no significant lipase, so the statement pairs the right action with the wrong enzyme.

Roots take up nitrogen chiefly as the nitrate ion and to a smaller extent as ammonium; inside the plant the nitrate is reduced and built into amino acids, proteins and nucleic acids.

Carbon dioxide is a trace gas, roughly four hundredths of one per cent of dry air by volume, yet it is the source of all the carbon that photosynthesis fixes into food and the chief gas by which human activity is warming the planet.

Transpiration is the escape of water vapour from a plant, chiefly through the stomata of the leaves, and over a forest or a crop field it returns a large volume of water to the air; together with evaporation from open surfaces it is called evapotranspiration.

About ninety-seven per cent of the water on earth is salt water in the oceans, and of the small freshwater remainder the greater part is locked up as ice in glaciers and the polar ice sheets, with most of what is left held as groundwater.

The very high temperature of a lightning discharge supplies enough energy to break the triple bond of nitrogen, and the atoms join oxygen to give nitric oxide and then nitrogen dioxide, which dissolve in rain as nitrous and nitric acid and reach the soil as nitrate; this is physical or…

Nitrogenase is the enzyme complex, containing molybdenum and iron, that breaks the triple bond of the nitrogen molecule and joins the atoms with hydrogen to make ammonia; it is destroyed by oxygen, which is why a root nodule keeps leghaemoglobin to mop oxygen up.

Dry air is about seventy-eight per cent nitrogen by volume, which makes the atmosphere the great reservoir of the nitrogen cycle, yet the triple bond of the nitrogen molecule is so strong that plants and animals cannot use the gas directly and depend on fixation.

Denitrification is the reduction of nitrate to nitrogen gas, which escapes to the atmosphere and completes the nitrogen cycle; it is carried out by these bacteria in waterlogged soils where oxygen is scarce, and it is the reason farmers lose nitrogen from flooded fields.

Nitrification happens in two stages, and the first is the oxidation of ammonia to nitrite by chemoautotrophic bacteria of the genera Nitrosomonas and Nitrococcus.