General Science GK Questions with Answers – Page 52

Yeast is a single-celled fungus, placed in kingdom Fungi in Whittaker's five-kingdom system. Yeast cells are eukaryotic, have a cell wall containing chitin and do not make their own food, which are the marks of fungi.

Lysozyme kills bacteria by breaking down their cell walls, and it is found in saliva, tears and mucus. Lysozyme attacks peptidoglycan, the main material of the bacterial cell wall, by splitting the bonds between its sugar units; the weakened cell then bursts.

Presbyopia is an age-related loss of near focusing, and it is corrected with bifocal or progressive lenses. With age the ciliary muscles weaken and the eye lens loses its flexibility, so the power of accommodation falls and the near point moves away.

Newton's law of gravitation is an independent law of nature; it cannot be derived from his three laws of motion.

The cervix is the lower, narrow neck of the uterus, so it belongs to the female reproductive system. The human male reproductive system has a pair of testes that make sperm and the hormone testosterone.

Only statements 3 and 4 are true; statements 1 and 2 are false. The modern periodic table arranges elements by atomic number.

Paper chromatography separates substances because each one divides, or partitions, itself differently between two liquid phases. In paper chromatography the stationary phase is the water held in the cellulose fibres of the paper, and the mobile phase is the solvent that rises up the paper by capillary action.

Sound in air is a longitudinal wave, and only transverse waves can be polarised. Polarisation means restricting the vibrations of a wave to a single plane.

The Moon gives out no light of its own; it only reflects sunlight, so it is a non-luminous object. A luminous object produces and emits its own light, while a non-luminous object is seen only because it reflects light falling on it.

Reversing the pole that approaches the loop reverses the change in magnetic flux, so the induced current reverses too. When a magnet moves towards a closed loop, the magnetic flux through the loop changes and an electric current is induced (Faraday's law of electromagnetic induction).

Mosses and liverworts have no xylem or phloem, so water moves through them cell to cell. Bryophytes, such as Funaria (a moss) and Marchantia (a liverwort), are called the amphibians of the plant kingdom because they live on land but need water for fertilisation.

Copper with dilute nitric acid gives copper nitrate, water and nitric oxide: 3Cu + 8HNO 3 → 3Cu(NO 3 ) 2 + 2NO + 4H 2 O. Nitric acid is a strong oxidising agent, so metals usually do not release hydrogen from it; instead the acid itself is reduced, and…

The heat needed is 50 cal to warm the ice to 0°C, 800 cal to melt it, and 200 cal to warm all 20 g of water to 10°C. Take the specific heat of ice as 0.5 cal/g°C, the latent heat of fusion of ice as 80 cal/g and the…

Vinegar is a dilute solution of ethanoic acid, commonly called acetic acid, in water. Vinegar contains about 5 to 8 per cent ethanoic acid (CH 3 COOH) and is made by the fermentation of sugar or alcohol by acetic acid bacteria.

Cells made by the meristem lose the ability to divide and take on a fixed shape, size and job, and this change is called differentiation.

In water plants, parenchyma cells enclose large air cavities; this special form is called aerenchyma, and it helps the plants float.

Iron is more reactive than copper, so it pushes copper out of copper sulphate, and the freed copper coats the nail brown.

Rutherford found the nucleus to be positively charged, not neutral. In his gold foil experiment of 1911, Rutherford fired alpha particles at a very thin sheet of gold.

Only statement III is wrong, because colloidal particles are too small to be seen with the naked eye. Mixtures are graded by particle size.

Sound travels faster in warmer air, so statement I is wrong, while II and III are right. The speed of sound in a gas is v = √(γP/ρ).