Category Chemistry

Why don’t identical twins have identical fingerprints?

Fingerprint formation is like the growth of capillaries and blood vessels in angiogenesis. The pattern is not strictly determined by the genetic code but by small variables in growth factor concentrations and hormones within the tissue. There are so many variables during fingerprint formation that it would be impossible for two to be alike. However it is not totally random, perhaps having more in common with a chaotic system than a random system.

It is believed that the development of a unique fingerprint ultimately results from a combination of gene-environment interactions. One of the environmental factors is the so-called intrauterine forces such as the flow of amniotic fluid around the fetus. Because identical twins are situated in different parts of the womb during development (although they are not static), each fetus encounters slightly different intrauterine forces from their sibling, and so a unique fingerprint is born.

            Your genes specify only your biochemistry and through it, your general body plan. The pattern of your fingerprints forms rather in the way that wrinkles form over cooling custard. At most you may predict, say, the fineness of the wrinkles and their general pattern. Fingerprints are just one example. Many of your features could mark you out from any clone. Your genome only controls gross characteristics such as the rates at which the skin and its underlying attachments develop and grow. Even if there is no way for genes to specify everything exactly, there is no way the genome could carry enough information for the details. If our genomes had to specify everything, we would not be here. But, while the consequences of imperfect specification are usually trivial, they may have more serious effects. A minor distortion of a blood vessel could give poor blood flow or an aneurysm, and the branching and interconnection of brain cells affect mental aptitudes. That is why, though bright parents tend to have bright children, dimmer ones may have a child genius and vice versa.

Why is the sting of a scorpion more painful than that of a snake sting? What are the chemicals in their poisons?

Scorpion’s venom acts on the nerve tips and roots whereas snake’s poison acts on dendrites and axons of the nerves. As defence and prey capture are the sole aim of these and other animals and insects, it is the purpose on hand that determines venom’s composition and type.

 Cobra venom consists of 10 different enzymes, several different types of neurotoxins, cardio-toxins, cytotoxins, dendrotoxins and fasciculins (for example, lysocephalins, lysolecithins which are phospholipids). Snakes of the elapidae family (for example cobras, kraits and mambas) have venoms that kill primarily through neuro-muscular paralysis. It contains 60-75 amino acids and target nicotinic cholinoceptors in the muscle cell membranes which are sensitive to a chemical transmitter, acetylcholine. (Acetylcholine is released from nerve endings in response to an electrical impulse in the nerves.) The amino acids in snake’s venom block the junction between the nerves and the muscle. Scorpion’s venom consists of an arsenal of toxic compounds which contain 37 amino acids called charybdotoxin.

            When a scorpion stings these acids incapacitate the nerve cells causing severe pain, by rigidly binding with sulphur bonds unlike the snake’s toxin which binds by a ligand series. Moreover snake’s venom is digestible, but scorpion’s venom is not          

How do trees reduce air pollution?

            Plants can prevent pollution of environment in many ways. However, the answer is restricted to prevention of air pollution by trees.

            The major components of atmosphere are nitrogen (78.08 per cent) and oxygen (20.95 per cent) (major) with minor components are argon and carbon dioxide (0.0314 per cent) and many trace elements such as neon, helium, nitrous oxide, methane, carbon monoxide, sulphur dioxide, ozone, ammonia and aerosols (colloidal sized particles) are also present.

            The ratio of these components is changing very fast due to increased human activities like fossil fuel burning, afforestation and changes in land use. They result in the liberation of tones of carbon dioxide, carbon monoxide, methane and aerosols into the atmosphere. The server human interference over the last century is said to have strained the buffering capability of nature.

            Trees help reduce the pollution in more than one way. First, they act as sink for carbon dioxide. Through photosynthesis they synthesize carbohydrates using carbon dioxide, water and sunlight. This way thousands of tonnes of carbon dioxide are trapped by the trees. By the same process, trees release oxygen, which is needed by other living organisms. They also help in cooling of the atmosphere by transpiration, a process in which water is given up by plants as vapour. I addition, aerosols and dust particles (components of atmosphere pollution) settle on the dense foliage of trees. Thus trees, especially the tall ones with dense foliage around houses and industrial establishments, reduce aerosol and dust pollution by acting as barriers or curtains.

Why do vegetables such as cucumber, snake gourd and bottle gourd sometimes taste bitter?

   Bitterness is cucumber and other cucurbitaceae vegetable is due to the presence of compounds called cucurbitacins. Chemically these are tetra-cyclic triterpenes having high oxidative levels. They occur in nature as free glucosidesor as complicated mixtures, at high concentrations, in fruits and roots, for example in a wild variety of cucumber called Cucumis hardwikii.

            High temperatures above 92 degrees have been implicated in the increase f bitterness in fruits, although there is no evidence to support this. Conversely more bitter cucumbers are seen growing during the cooler growing season.

How can we identify poisonous and non-poisonous mushroom?

         

 

 

 

 

 

  Most of the mushrooms have a cap called pileus and a stem called stipe. The cap on its underside consists of gills which bear the spora producing structures. Important to the identification of a species are the properties of cap, the shape and colour of the gills, the way in which they are joined to the stem, presence or absence of sheath, scales and annulus ring etc. The most poisonous mushrooms are species of Amanita which come under the family Amanitaceae and the most delicious edible mushrooms are species of Agaricus (Button mushroom) which come under the family Agaricaceae. In general the fruit bodies of Amanita species can be distinguished from the Agaricus species by the following characters.

In Amanita species the pileus on its upper surface bears the scales and the stipe bears at its base a sheath called Volva. These scales and sheaths are absent in the fruit bodies of Agaricus species.

Volvariella (Paddy straw mushroom) is also having Volva at the base of the stipe as in Amanita. But it is an edible mushroom and also commonly cultivated. The Oyster mushroom namely Pleurotus is another edible one. This can be identified by its stem at the side of the cap and gills on the under surface of the cap. Boletus (Penny bun mushroom) and Lactarius (milk cap) are also edible members which grow in wild condition but not cultivable. Among these Boletus can be identified by its dense layer of tubes instead of gills on the underside of the cap.

The familiarity in distinguishing the poisonous and nonpoisonous mushrooms is needed only when we collect the wild fungi from the field for our diet table. But this problem will not arise in the case of edible fungi which are cultivated for this purpose.

What makes a cola foam up when you put a pretzel in it?

The cola foaming up when a pretzel is put in it is a physical interaction, not a chemical reaction. It works with other carbonated beverages too. Carbonated beverages when opened and released from pressure or supersaturated solutions of gas with more carbon dioxide dissolved in the beverage than would be possible at normal pressures.

 Left alone for two hours, the drink would slowly lose the gas and go flat. Sodium chloride particles seem to provide an especially good surface for gas to collect on, form bubbles and quickly rise to the surface and escape.