Everyday Science Mixed Quiz 4: Body, Microbes, Light and Heat, WBPSC Clerkship GS

When we get a cut, platelets gather at the wound and start the clotting of blood. Red blood cells carry oxygen with the help of haemoglobin, and white blood cells fight germs. Plasma is not a cell at all but the liquid part of blood.

The liver is the largest gland in the human body; it makes bile, which helps digest fats. The thyroid is the largest endocrine gland, in the neck, and the pituitary is called the 'master gland' because it controls other glands. The largest organ, however, is the skin.

Vitamin K is needed in the liver to make the clotting proteins (such as prothrombin); without it bleeding from a cut does not stop easily. Lack of vitamin A causes night blindness, of C scurvy, and of D rickets.

Lack of vitamin B1, thiamine, causes beriberi, which weakens the nerves and the heart. It is seen where highly polished rice is the main food, because thiamine lies in the outer layer of the grain. Lack of vitamin C causes scurvy and of D rickets.

Malaria is caused by Plasmodium, a single-celled protozoan that enters the human body through the bite of the female Anopheles mosquito. Male mosquitoes do not feed on blood but on plant juices, so they do not spread disease. Aedes spreads dengue and Culex filariasis.

In pasteurisation milk is heated to a set temperature (for example about 72 °C for 15 seconds, or about 63 °C for 30 minutes) and then cooled quickly. This kills most harmful germs without changing the taste as boiling does. The process is named after Louis Pasteur.

Lactobacillus bacteria turn lactose, the sugar in milk, into lactic acid; the acid sets the milk protein into curd and gives it its sour taste. Yeast makes bread rise, Rhizobium fixes nitrogen in roots, and penicillin comes from Penicillium.

Yeast is a single-celled fungus; it breaks down the sugar in the dough (fermentation) and gives off carbon dioxide and a little alcohol. The gas bubbles are trapped and the dough rises, so bread becomes soft and spongy. No oxygen, nitrogen or hydrogen is produced here.

In myopia the image of a distant object forms in front of the retina, so distant things look blurred. A concave lens spreads the light a little, pushing the image back onto the retina. Hypermetropia (near things blurred) is corrected with a convex lens.

A clay pot has countless tiny pores; water seeps through them and evaporates from the outer surface. The latent heat needed for evaporation is taken from the pot and the water inside, so the water cools. Our body cools when sweat dries for the same reason.

A thermos flask has a vacuum between its two glass walls; with no medium there, conduction and convection hardly happen. The shiny silvered walls reflect radiant heat back. So the flask cuts down all three modes as far as possible, keeping hot things hot and cold things cold.

A carrot is a tap root swollen with stored food (a modified root), with no nodes or buds on it. Radish, beetroot and sweet potato are roots too. Potato, ginger and onion, however, are modified stems, because they bear buds ('eyes').

Leguminous plants such as pea, gram, moong and soybean have Rhizobium bacteria in their root nodules. They turn the nitrogen of the air into compounds plants can use, so these crops make the soil more fertile. Rice, wheat and maize are cereals, not legumes.

The human heart has 4 chambers: two atria above and two ventricles below. The right side sends the deoxygenated blood from the body to the lungs; the left side sends the oxygenated blood from the lungs to the whole body. A fish's heart has 2 chambers and a frog's 3.

Each kidney has about a million nephrons; they filter the blood, separating wastes and extra water to form urine. The neuron is the unit of the nervous system, the alveolus is an air sac of the lung, and the villus is the absorbing part of the small intestine.

A lactometer measures the specific gravity of milk; adding water lowers it, so adulteration shows up. A hygrometer measures humidity of the air, a hydrometer the specific gravity of liquids in general, and a thermometer temperature.

When light passes from water into air its speed changes and its path bends; this is refraction. So the part under water appears a little higher than it is and the spoon looks broken or bent. Splitting into seven colours in a prism is dispersion, and the blue sky is due to scattering.

The formula is $F = \frac{9}{5}C + 32$. Setting $F = C$ gives $C = \frac{9}{5}C + 32$, so $-\frac{4}{5}C = 32$ and $C = -40$. So −40 °C = −40 °F, while 0 °C is 32 °F.

In 1928 Alexander Fleming noticed that the mould Penicillium was killing the bacteria around it; this is how penicillin was discovered. Edward Jenner developed the smallpox vaccine, Louis Pasteur the rabies vaccine and pasteurisation, and Robert Koch identified the germs of tuberculosis and cholera.