General Science GK Questions with Answers – Page 53

Fungal cell walls are built mainly of chitin, whereas plant cell walls are built of cellulose. Chitin is a tough polysaccharide made of units of N-acetylglucosamine, a sugar that carries nitrogen.

This filarial roundworm causes elephantiasis, also called lymphatic filariasis. The adult worms live in the lymphatic vessels and block the flow of lymph, so the legs, arms or genitals swell and the skin thickens, giving the disease its name.

It is part of the kidney's nephron and filters blood to form urine; it plays no role in breathing. Bowman's capsule is the cup-shaped start of each nephron, wrapped around a tuft of capillaries called the glomerulus.

Boiling removes only temporary hardness; permanent hardness comes from salts that do not break down on heating. Temporary hardness is caused by the bicarbonates of calcium and magnesium.

For a real object, a concave lens always forms a virtual image, so this statement is wrong. A concave lens is a diverging lens: it spreads out parallel rays so that they seem to come from its focus on the same side as the object.

The N shell is the fourth shell (n = 4), and a shell can hold at most 2n² electrons, which gives 2 × 16 = 32.

The oesophagus, like the mouth, is lined by flat squamous epithelium that protects it from wear as food passes. Epithelial tissue covers body surfaces and lines organs, and its cells are named by shape.

Animal cells do have vacuoles; they are only small and often temporary, so the statement is wrong. A vacuole is a membrane-bound sac filled with cell sap: water, salts, sugars and waste.

The eye adjusts the focal length of its lens to bring both near and far objects into focus on the retina, and this ability is called accommodation.

Benzene and water do not mix, so they form two layers that a separating funnel can draw off one after the other.

James Chadwick discovered the neutron in 1932, the uncharged particle that sits in the nucleus alongside the proton. Chadwick bombarded beryllium with alpha particles and found that it gave off a penetrating radiation of neutral particles with a mass almost equal to that of a proton.

Among the four, microwaves lie farthest towards the long-wavelength end of the electromagnetic spectrum. In order of increasing wavelength the spectrum runs: gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves.

Graphite has the lowest energy of all forms of carbon at ordinary temperature and pressure, so it is the thermodynamically most stable allotrope.

Using R = L/(σA) with equal lengths, the resistance of Y comes out three times that of X. Resistance falls as conductivity σ and cross-sectional area A rise.

Probiotics include both bacteria and yeasts, and some of them help break down lactose, the sugar in milk. Probiotics are live microorganisms that give a health benefit when eaten in adequate amounts.

The thunder arrived 6 seconds after the flash, and sound covers 320 m every second, so the distance is 320 × 6 = 1920 m. Lightning and thunder are produced at the same moment.

Wool is an animal fibre made mainly of the protein keratin. Polymers are giant molecules built from many small repeating units called monomers.

Sucralose is made from ordinary table sugar, sucrose, by changing its molecule. In making sucralose, three hydroxyl (OH) groups of the sucrose molecule are replaced by chlorine atoms.

Twelve pairs of cranial nerves arise from the brain and serve the head and neck, among them the optic nerve of sight, the auditory nerve of hearing and the vagus, the longest cranial nerve, which reaches the heart and the abdomen; thirty-one pairs of spinal nerves arise from the spinal…

The hyoid is a U-shaped or horseshoe-shaped bone lying in the front of the neck below the lower jaw; it is held in place only by muscles and ligaments and forms no joint with any other bone, which is why it supports the tongue and helps in speech and swallowing.