Keshav Jain

            About three-fourths of a poultry egg is plain water in which the albumin protein and fats are suspended. At room temperature, the protein strands are tightly folded in a complex three-dimensional shape. Because the individual proteins are able to move freely, both the egg-white and the yolk remain liquid. But when the egg is placed in boiling water, the protein strands begin to straighten out. The protein ends, normally protected within the folds, become exposed. When the temperature rises to , the open ends join together in bridge-like bonds forming a giant structure. These new bonds prevent the molecules to move                                                                                              thereby making the egg material solid.

            Fanning produces a sense of coolness in the body because of evaporation of moisture from the skin. On fanning the rate of evaporation increases. The water molecules from the body in the form of perspiration take up heat energy from the body and escape from the body surface, thus cooling it. However, if the air is hot, as in a desert, fanning does not produce any cooling as the heat for evaporation is supplied by the hot air.

   The intensity of light coming out from a TV screen is very high. If this bright light with varying intensity is the only source of light in a darkened room, the eye has to constantly adjust for vision by opening wide or narrowing the iris when a person focuses on the bright screen or looks away from it. The constant adjustments that the eye has to make causes eye strain. Whereas in a lighted room, intensity of the T.V. image is only a little brighter than the surroundings, which makes the viewing easier for the eyes. It is, therefore, advised to have some light in the room while watching the television.

            The softness of ice cream arises out of the nature of the ingredients and the way they are combined. Two essential ingredients of ice-cream are fat in the form of cream and air bubbles introduced by stirring.  As the water in the ingredients starts freezing, the suspended fat globules prevent the whole content from freezing as a single mass. Tiny air bubbles trapped in the mixture due to continuous stirring of the ingredients also prevent the ice crystals from growing as the temperature is reduced further. This prevents the ice cream from becoming hard and the frozen mass remains soft.

  In the case of ice, the absence of fat and air bubbles leads to the tiny ice crystals growing into large chunks of hard ice.

            There is a close link between the sense of taste and the sense of smell. Much of what we think of as taste has a big smell component. The taste buds in the tongue monitor relatively crude sensation of the four basic tastes – sweet, salty, sour and bitter. Faint vapours of whatever we eat drift into the nasal cavity where the smell receptors add more detail to the information given by the taste buds.

When we have a cold our nose becomes blocked and the sensation of smell ceases. The gas and vapours from the food cannot be sensed by the smell receptors; consequently we cannot perceive the smell or aroma of the food, which in turn makes the food appear tasteless.

            Tears produced by the tear glands keep the eyes moist and are normally drained off through the nose. Onions contain a number of water soluble volatile substances containing sulfur. On cutting the onion these substances quickly spread into the air and cause irritation in eyes. The tear glands start secreting more and more tears to wash out the irritants. The tears are produced so rapidly that they cannot be drained out through nose and so run down the eyes.

Potato is a living plant tuber (a modified stem specialized for storage of food). There is a lot of difference in the cellular structure and chemical nature of the potato peel and that of the flesh. The flesh is made up of parenchyma cells, specialized to store starch. The walls of these cells are made up of cellulose and they are joined together by a sort of glue called pectin. The peel or the skin of potato is made up of cork cells, the walls of which have a lot of lignin and suberin deposits. These substances give a greater mechanical and structural strength to the corky cells and hence are easy to remove as a continuous peel. In un-boiled potato the corky skin and the flesh of potato are sealed together by pectin. Hence peeling is difficult. During boiling, little change occurs in the corky peel, but the fleshy parenchyma becomes soft. Also the glue-like substances present between the cells, swell up and break down. As a result, the adhesion between the peel and the flesh is reduced and the effort required to separate the peel from the flesh is highly reduced. Hence it is easier to peel a boiled potato.

            Spoilage of foodstuffs is caused by microorganisms which decompose them to produce acid, alcohol, etc. Bacteria are always present in the atmosphere. When freshly prepared food is kept in the open for long periods it gets contaminated. The bacteria then act upon the foodcomponents such as proteins, carbohydrates and fats and break them down to products which due to their off-odours or bad-taste are not suitable for consumption. Factors such as high temperature and humidity help the bacteria to grow.

    Spoilage of food can be prevented by treatments like heat sterilization, refrigeration, deep-freezing and desiccation.

  Flowering is a natural mechanism by which the majority of plants perpetuate their species through the production of seeds. All the parts of a flower take part in one way or another in the reproductive process. The stamens consist of thread-like stalks supporting sac-like anthers which produce the pollen. The central pistil contains the ovary and a sticky stigma. The colourful petals serve as signals to attract insects and other pollinators. When pollinating insects or birds visit the flowers for nectar, they help transfer pollen to the stigma which leads to fertilization of the egg cells in the ovary. The ovary then grows into a fruit containing seeds that would, if planted, grow into new plants thus perpetuating the species.

            Like any living organism, plants need, besides air and sunlight, water and nutrients for growth and survival which they take up through their roots. For land plants, the soil provides the moisture and nutrients. The soil also protects the roots from rapid fluctuations in temperature, as just below the surface the temperature scarcely changes from day to night. But more importantly, soil provides the firm support which holds the plants on the ground. Some plants, like the water hyacinth which grow in water, and orchids which grow on trees do not need soil to grow on as they can get their nutrients from water or the host                                                                                              plant.