Category: WHY CORNER

Having two eyes is certainly better than having just one because two eyes provide us with stereo vision and depth perception —things that wouldn’t have been possible with just one eye.

With a gap of around two and a half inches separating our eyes, each eye views an object from a slightly different angle. For instance, if you hold up a flower and look at it with just your right eye, the image is different from the image you get when you look at it with just your left eye. The right eye sees more of the right side of the flower while the left eye sees more of the left side of the flower. If you placed the two different images on top of one another, they would not match and our vision would be out of focus. However, our brain sorts out these varying visual messages from our two eyes, combines the images and the recreates a single three-dimensional image.

This is referred to as binocular vision. Just as you look through two lenses in binoculars, humans view the world through two lenses. The eyes of many other animals are placed differently than ours. Many birds have an eye on each side of their head. Each eye sees a completely separate area stretching out on the left or the right.

Viewing the world through two eyes provides us with depth perception. When you look at the flower through just one eye, it looks a lot flatter.

The Telegraph (Kolkata, India)

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A slice of apple becomes reddish or brownish after a few minutes because of a chemical reaction called oxidation brought about by the oxygen in the air.

Apples and many other fruits contain chemicals called polyphenolic compounds. Phenols are colourless, but on oxidation under the influence of an enzyme called polyphenol oxidase (PPO) — also known as tyrosinase — they turn brown in colour.

Once you cut the fruit, you open up some of the cells. This breaks the structure of the enzymes which are otherwise coiled. The enzyme then has access to the oxygen in the air and produces quinones, which turn the cut surface brown. It is also for this reason that brown spots appear on apples when you drop them.

The easiest way to prevent browning is to put the sliced apples in water so that the enzyme does not have access to oxygen. Also, the enzymes can be deactivated by heating or adding lemon juice. One can also use preservatives like sulphur dioxide for reducing the amount of available oxygen.

Using cutlery that has some corrosion (as is seen with lower-quality steel knives) can increase the rate and amount of the browning by making more iron salts available for the reaction. A similar effect is noticed with cut potatoes, pears, bananas and peaches, which also darken on exposure to air.

In humans, tyrosinase is important because it helps create melanin, which causes tanning. The lack of tyrosinase in humans leads to albinism. So in humans, the browning that tyrosinase helps cause is actually a good thing!

Source: The Telegraph (Kolkata, India)

A banana skin turn black after a few days, even when the banana is kept in the refrigerator.

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The reason behind it is that the green skin of banana contains a gaseous plant hormone, ethylene, which diffuses into the fruit and hastens the process of ripening. It is yellow when the fruit is ripe and turns black with the production of more and more ethylene. The large number of enzymes of Kreb’s cycle convert citric acid, mallic acid and oxalic acid into glucose in a banana, to make it sweet during the process of ripening. When the banana is kept in the refrigerator, the enzymatic reactions are stopped by the cold but the production of ethylene hormone continues.
This turns its skin black.But food value of banana does not change unless it is decomposed.

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• Question Corner

Onions come in many varieties and three main colours   yellow, white and red. They are rich in nutrients including vitamins B and C, protein, calcium and iron.

It’s not the strong odour of the onion that makes us cry, but the substances that are released when we chop it. The vegetable contains some sulphur compounds which are released when we cut it. Sulphur, being an irritant to both our nose and eyes, makes our eyes tear up.

What actually happens when the sulphur compound comes in contact with the water in our eyes is this  it produces very dilute sulphuric acid. This acid then irritates the eyes. In response to this acid, our eyes automatically blink and produce tears, which wash the eye and flush out the acid.

An automatic reaction many people show is to rub their eyes with their hands. This often makes the situation worse, as our hands are covered with the sulphur compounds, which we then rub directly into our eyes.

The only remedy is to boil the onion, not slice it. But this is not a very practical solution. Some people suggest putting the onion in the freezer for a few minutes because the cold decreases the speed of the chemical reaction. Another tip is to slice the area around the root last, as this contains more sulphur.

British farmers have developed the new kind of onion, called Supasweet onions. It is said to be so mild that it can be eaten like an apple. Supasweet onions have been available in supermarkets around England since 2003. The onion has a pale, thin skin, is easy to peel and quick to prepare. These onions are not genetically modified. Their secret is that they have been specially grown in low-sulphur soils!

Source:The Telegraph (Kolkata,India)