General Science GK Questions with Answers – Page 37

The skin is the largest organ of the human body by both surface area and weight, and it is the organ of touch; it is made of an outer epidermis and an inner dermis that carries blood vessels, nerve endings, hair follicles, sweat glands and sebaceous glands.

Rhodopsin, the pigment of the rod cells that makes vision in dim light possible, is formed from a derivative of vitamin A, so when the vitamin is lacking the rods cannot work properly and the person is unable to see in faint light, a condition called night blindness or nyctalopia…

The Eustachian tube, also called the auditory tube, runs from the cavity of the middle ear to the nasopharynx, the upper part of the throat behind the nose, and its function is to keep the air pressure on the inner side of the eardrum equal to the pressure outside.

The blind spot, also called the optic disc, is the small area of the retina from which the fibres of the optic nerve pass out of the eyeball; it has neither rods nor cones, so an image falling on it is not registered and we do not notice the gap…

In myopia the eyeball is too long or the lens too strongly curved, so light from a distant object is brought to a focus in front of the retina and the distant object appears blurred.

Rhodopsin, also called visual purple, is the pigment of the rod cells; it is extremely sensitive to light, which is why rods allow us to see in dim light, though only in shades of black and white.

The retina is the innermost coat of the eyeball and it carries the photoreceptor cells, the rods and the cones, which convert light into nerve impulses that the optic nerve carries to the brain; the image formed on the retina is real and inverted, and the brain interprets it as…

The three semicircular canals of the inner ear are set at right angles to one another and are filled with fluid; movement of the head moves the fluid, which stimulates the receptors and tells the brain about the position and motion of the head, so that balance or equilibrium is…

The stapes, also called the stirrup because of its shape, lies in the middle ear and is the smallest bone in the human body; it passes the vibration received from the eardrum on to the oval window of the inner ear.

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.

The iris is the coloured ring in front of the lens, formed by the front part of the choroid, and the muscles in it widen or narrow the pupil so that the right amount of light reaches the retina; in dim light the pupil opens wide and in bright light…

All three follow from Einstein's General Theory of Relativity, published in 1915. General relativity explains gravity not as a force but as the curving of space-time by mass and energy; in John Wheeler's words, matter tells space-time how to curve, and space-time tells matter how to move.

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.

Carborundum, or silicon carbide (SiC), is one of the hardest substances known, so it can grind, cut and polish other materials, which is what an abrasive must do.

Too little fluoride in drinking water leaves tooth enamel weak, so teeth decay more easily and develop cavities, called dental caries.

Potassium carbonate comes from a strong base and a weak acid, so statement 1 is wrong, while statements 2 and 3 are right.

When water is short, leaves make more abscisic acid (ABA), which makes the guard cells lose water and close the stomata, so the plant loses less water through transpiration.

Every biological molecule, from sugars and fats to proteins and DNA, is built on a skeleton of carbon atoms, which is why carbon is called the basic building block of life.

A hydrogen bomb fuses light hydrogen nuclei, while a uranium bomb splits heavy uranium-235 nuclei. In nuclear fission a heavy nucleus such as uranium-235 absorbs a neutron and splits into two lighter nuclei, releasing energy and two or three more neutrons.