General Science Previous Year Questions (PYQ) with Answers – Page 53

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.

Ethyl alcohol, or ethanol, dissolves resins, gums, dyes and oils and also evaporates quickly, so paints, varnishes and polishes made with it dry fast; this makes it the common solvent of the paint industry.

Hydrogen has three isotopes: protium with one proton and no neutron, deuterium with one proton and one neutron, and tritium with one proton and two neutrons.

The female egg cell, or ovum, is the largest cell in the human body. It measures about 100 to 130 micrometres across, roughly the thickness of a hair, and is the only human cell that can just be seen without a microscope.

Both carry a small circular DNA of their own and their own 70S ribosomes, so they make a part of their protein themselves and divide independently of the cell; this semi-autonomous nature is the main evidence for the view that they descend from free-living bacteria engulfed by an early cell.

The poise is the CGS unit of dynamic or absolute viscosity, named after the French physician Jean Poiseuille, and one poise equals one dyne-second per square centimetre, which is the same as one gram per centimetre per second.

A concave lens is a diverging lens, so for every position of a real object it forms an image that is virtual, erect and diminished.

The domestic goat is treated as a subspecies of the wild goat, so its name carries three parts — the genus Capra, the species aegagrus and the subspecies hircus.

The alveoli are the tiny balloon-like air sacs at the ends of the smallest airways, and their thin walls are the surface where gases are exchanged.

Lead and mercury are in fact the poorest conductors of heat among the metals, so calling them the best is wrong.

Epithelium covers the body and lines its organs, so it is the protective tissue. It forms the outer layer of the skin, the lining of the mouth, stomach, intestine, blood vessels and kidney tubules.

Calaverite is gold telluride, with the formula AuTe2. It is one of the very few minerals in which gold occurs chemically combined rather than as the free metal, because gold is a noble metal that usually resists reaction.

Barium compounds such as barium nitrate give fireworks and signal flares a bright green flame. The colour comes from a flame test.

A normal umbilical cord contains two arteries and one vein, three blood vessels in all. The umbilical cord joins the developing foetus to the placenta.

Sulphur dioxide dissolves in water to give sulphurous acid, a weak acid with the formula H2SO3, by the reaction SO2 + H2O to H2SO3.

A denser medium has a higher refractive index, and the refractive index is the speed of light in vacuum divided by its speed in the medium, so light must travel more slowly inside it.

Vitamins A, D, E and K dissolve in fat, while the B group and vitamin C dissolve in water.

Monosodium glutamate is the sodium salt of glutamic acid, an amino acid, and it is added to soups, sauces, noodles and snacks to strengthen their savoury taste.

Anabaena is a cyanobacterium, a prokaryote with no true nucleus, and all prokaryotes are placed in Monera. In R.H.

Nitrogen is an unreactive gas, so it drives the oxygen out of the packet and stops the oil in the chips from getting oxidised.