uKnoWhy.com » Nature

U know why the fish stinks?

admin — Wed, 21 Apr 2010 23:31:39 +0000

The smell of fish (fish odor) is not due to the fact that the fish died and then begin it’s decomposition but is due to trimethylamine, a compound that is volatile form after the death of fish, some proteolytic bacteria (demolition of protein structures) of the genera Achromobacter, Pseudomonas, Micrococcus, Bacillus putrefaciens Altreromonas and begin to colonize the meat.

The process continues on a regular basis over the period of edibility of fish, and this explains why the smell (fish odor) increases with time. Then stabilizes.

Cool?

The measure of the amount of trimethylamine is the most common for determining the freshness of the fish: if less than 5.10 mg / 100 g, according to experts FAO (UN Food and Agriculture) should be marketed.

The intensity of the smell indicates the degree of freshness and therefore quality fish.

Curiosity
It is not only the fish that lay decomposing on odor, there is trimetilaminuria, in people suffering from a disease that may have genetic origin, it spreads the same scent: in fact they are deficient in enzymes that transform trimethylamine, it is naturally present in the human body, in odorless compounds.

U know why the fireflies glow?

admin — Tue, 10 Mar 2009 13:04:01 +0000

The firefly is an insect which is particularly known for its characteristic luminescence. This animal has special abdominal organs, which cause a chemical reaction with the organic synthesis of an enzyme called luciferasi.

The light produced is useful because from these insects it can be exploited as a mean of communication between individuals of the same species, probably as a sexual recall as well, that could draw the prey too. It is curious to note that the adult insect issues, generally, intermittent light, while the larvae shine light sets.

U know why ‘ostriches’ hide their heads in the sand ?

admin — Sat, 22 Nov 2008 13:10:14 +0000

The reason for this behavior on the part of ostriches is ignored by everyone, why? Simple … because it’s false! Indeed, the popular belief that ostriches put their heads in the sand in case of danger, is wrong and has never been recorded.

However, when there is no other possibility of escape evident, a bird can lie down on the ground with head and neck stretched forward and remain firm in the hope that it is ignored by his enemy. This strategy has similarly taken by a bird in hatching when feel that the danger is nearby.

But it is plausible that this belief is born from a visual interpretation wrong: in fact, when an ostrich lowers his head between the foliage to eat, it seems, for an optical effect, like he has its head hidden between the sand.

U know why ‘you cry cutting the onion’ ?

admin — Tue, 18 Nov 2008 21:58:40 +0000

In onion there are molecules that contain one or more of sulfur atoms: the organic sulphides. When cutting the onion these sulphides are combined with another substance present in different layers, “the allinasi enzyme”, which degrades amino acids and volatile odorless. These amino acids, reacting with water covering the cornea, are transformed into acids, mainly sulfuric and sulphide. As corrosive substances, the eye tries to rid activating the lacrimal glands. From the’90 in different parts of the world , it attracts the attention of scientists, agronomists and geneticists. How it is possible to avoid tearing ? . In a research to assess the volatile components in some onion cultivars an investigator at the University of Naples, Giancarlo Barbieri, showed 46 volatile compounds, including many sulfur compounds, aldehydes and some alcohol. They noted differences between varieties of yellow and white tunic. For example, the level of volatile compounds in cultivar Density is about twice that in pure Blanco and Reddy. The cultivar late or have a Serb acid content Pyruvic twice as sweet. E ‘result that even the mineral sulphate fertilizer can help improve the level of alcohol pungency, especially in the case of onions. A researcher of Georgia has shown experimentally that after the administration of calcium sulfate to the soil concentration of acid in Pyruvic bulbs has doubled.

U know why ‘the sky’ is blue?

admin — Tue, 18 Nov 2008 18:50:40 +0000

The visible white light coming from the Sun is composed from superposition of electromagnetic waves of different wavelengths ranging from the radiation that we perceive as violet, to the radiation that we recieve as red then blue, green, yellow, orange. The dust particles and droplets of water present in the atmosphere are much larger than the wavelength of visible light: in this case the light is reflected in all directions equally, regardless of its wavelength. The gas molecules are smaller and the light behaves differently depending on its wavelength. The red light has a wavelength greater and tends to “bypass” the smaller particles without “seeing” this light, therefore, very weakly interacting with the atmosphere and its spread continuing straight along the original direction. In contrast, the blue light has a wavelength less “aware” of the presence of molecules that is reflected in all directions. Then, crossing the atmosphere, most of the majority wavelength radiation continues its trajectory straight ahead. The red light, orange and yellow are affected only minimally by the presence of air. In contrast, the blue light is diffused in all directions. In whatever direction we look, part of this light reaches our eyes. The sky therefore appears blue.