General Science Mixed Quiz: Set 89

Bacteria turn the lactose in milk into lactic acid, a new substance, so souring is a chemical change that cannot be reversed.

Red biotechnology is the branch applied to medicine and health care, including the making of insulin, antibiotics and vaccines. Biotechnology is often divided by colour according to its field of use.

Chromosomes are made of DNA wound around proteins, mainly histones; together this DNA-protein material is called chromatin. In eukaryotic cells, a very long DNA molecule wraps around groups of eight histone proteins to form beads called nucleosomes.

A beam seen from the side is visible only because tiny particles send some of its light sideways. Light travelling in a straight line cannot enter our eyes unless something redirects it towards us.

Crude petroleum is a mixture of hydrocarbons with different boiling points, and fractional distillation separates them. In a refinery, crude oil is heated to about 400 °C and its vapour enters a tall fractionating column that is hot at the bottom and cooler towards the top.

Rotational kinetic energy is ½Iω², and the ring has the larger moment of inertia. For a thin ring about the axis through its centre and perpendicular to its plane, all the mass sits at distance R, so I = MR².

Cicadas, froghoppers and pond skaters all have three body parts, six legs and a pair of antennae, the marks of the class Insecta.

One parsec equals about 2,06,265 astronomical units, which rounds to 2 × 10⁵ A.U.

All three statements are correct; microbes called extremophiles live in all these conditions. Hyperthermophiles, many of them archaea living near deep-sea hydrothermal vents, grow above 100 °C; Methanopyrus kandleri and 'Strain 121' grow at about 120 °C, where high pressure keeps water liquid.

An ion-exchange resin or zeolite swaps the calcium and magnesium ions that cause permanent hardness for sodium or hydrogen ions.

An adult set of thirty-two permanent teeth has eight incisors for cutting, four canines for tearing, eight premolars and twelve molars for grinding, so there is one canine on each side of each jaw.

Capra hircus is the scientific name of the domestic goat, in which Capra is the genus and hircus the species, written in the two-word form that Carl Linnaeus gave to biology.

The correct answer is B, the Leydig or interstitial cells, which lie in the spaces between the seminiferous tubules of the testis and secrete androgens, chiefly testosterone, under the influence of luteinising hormone from the anterior pituitary.

The velocity ratio of a pulley system is the distance moved by the effort divided by the distance moved by the load, so it is 12 divided by 3, that is 4.

Jupiter is a planet; it does not make its own light and shines only by reflecting sunlight. A luminous object produces light of its own, as stars do by nuclear fusion in their cores, where hydrogen is turned into helium.

The receptors that pick up taste are called gustatory receptors, and they sit inside the taste buds on the tongue.

Groundnut, horse-gram and soybean are all legumes of the family Fabaceae (Leguminosae), the pea family. Members of the pea family bear their seeds in pods and carry root nodules in which Rhizobium bacteria fix atmospheric nitrogen.

Argon is an inert gas, so it does not react with the white-hot tungsten filament and slows its evaporation, which makes the bulb last longer.

X-rays are electromagnetic waves with no electric charge, so electric fields cannot deflect them. X-rays were discovered by Wilhelm Röntgen in 1895, who won the first Nobel Prize in Physics in 1901 for it.

Friction acts only where two surfaces touch, while a magnet can push or pull an object across a gap. Forces are grouped by whether the bodies must touch.