General Science Previous Year Questions (PYQ) with Answers – Page 48

ACE2 is the receptor through which the coronavirus SARS-CoV-2, the cause of COVID-19, enters human cells. ACE2 stands for angiotensin-converting enzyme 2, a protein on the surface of cells in the lungs, heart, blood vessels, kidneys and gut, where it normally helps control blood pressure.

Statements 1 and 3 describe real differences; statement 2 gets the life span backwards. A sodium vapour lamp is a glowing tube that sends light out in all directions, through 360 degrees, so reflectors are needed to push the light down onto the road and some light is wasted.

Statement 1 has both genomes wrong, while statement 2 is a correct fact. Adenoviruses carry a double-stranded DNA genome.

. Orbits of fixed energy were proposed by Niels Bohr in 1913; Rutherford's experiment said nothing about the energy of electrons.

In the list of natural sources of acids that school science teaches, tomato is matched with oxalic acid.

Bacteria and fungi grow on artificial media, but viruses multiply only inside living cells. Bacteria and fungi are living cells with their own machinery for making energy and proteins, so they grow on nutrient agar, broth or synthetic media in a laboratory.

Mitochondrial DNA comes only from the mother, and mitochondrial replacement therapy can stop a mitochondrial disease from passing to the child.

Distance is the length of the actual path and displacement is the straight line from the start to the finish, so on a curved path the two can never be equal: the arc of a circle is always longer than the chord joining its ends.

Here water only combines with calcium sulphate hemihydrate to form gypsum; no gas is given off and the paste simply sets hard.

Fly ash is the fine powdery residue left after coal is burnt in thermal power stations; it is a mixture of oxides, not a pure form of carbon.

Recombinant vector vaccines are made by genetic engineering, and both viruses and bacteria serve as their vectors. In a recombinant vector vaccine, scientists take a harmless or weakened carrier, the vector, and insert into it the gene for an antigen of the disease-causing germ.

Moringa is not a legume and tamarind is not native to South Asia, so statements 1 and 2 are false.

Hydrogen adds across the carbon–carbon double bonds of the oil. Vegetable oils are unsaturated: their fatty acid chains contain C=C double bonds, which keep them liquid.

Soaps are sodium or potassium salts of long-chain carboxylic (fatty) acids, not ammonium salts. A soap molecule has a long hydrocarbon tail that mixes with oil and an ionic head that faces water.

In the Raman effect, a small part of the light scattered by molecules comes out with a changed frequency. C.V.

Reverberation is the lingering of sound in a closed space caused by many reflections from the walls, ceiling and floor.

Gustatory receptors are the receptors of taste, and they lie in the taste buds of the tongue, which sit mostly on small projections called papillae; they are stimulated by chemicals dissolved in saliva and send impulses to the brain.

Current multiplied by resistance gives voltage, by Ohm's law, not electrical power. Electrical power is the rate at which electrical energy is used, and its basic formula is P = VI, where V is the potential difference and I is the current.

Charge equals current multiplied by time, and 1.0 A for 600 seconds gives 600 coulombs. Electric current is the rate of flow of charge, so I = Q ÷ t, or Q = I × t. Time must be in seconds: 10 minutes is 10 × 60 = 600 seconds.

In glass, violet light has the shortest wavelength and the highest refractive index, so it bends the most; dispersion is a result of refraction.