英語(yǔ)聽(tīng)力文摘 變性蛋白
The Denatured Egg White
煮雞蛋還有那么多學(xué)問(wèn)哪?在煮雞蛋過(guò)程，雞蛋會(huì)發(fā)生哪些變化呢?
蛋白質(zhì)變性(protein denaturation)是指蛋白質(zhì)在某些物理和化學(xué)因素作用下其特定的空間構(gòu)象被改變，從而導(dǎo)致其理化性質(zhì)的改變和生物活性的喪失，這種現(xiàn)象稱為蛋白質(zhì)變性。
Have you ever wondered how heating an egg white turns that uncooked clear goo into an opaque gel?
Well, that transparent goo is made of mostly water and proteins. Each protein is a long strand of amino acids that you can think of as a string of green and red Christmas lights. The green lights are hydrophilic amino acids, which attract water, and the red lights are hydrophobic amino acids, which hate water.
Each protein is coiled up in a big clump so that most of the water-loving green lights point outwards from the mass while most of the water-hating red lights point towards the inside to keep dry.
These coiled up proteins float around in small clumps allowing light to easily pass through the goo and provide little structure, so the goo is clear and liquidy.
Heating the goo causes the coiled up proteins to unwind, or “denature”, exposing the water-hating red lights to water.
To keep dry red lights from neighboring proteins glue together forming small nets of denatured proteins.
Heat continuously applied to the goo produces a snowball effect as more proteins are denatured and aggregate together producing many additional small protein nets, which in turn glue together into bigger and bigger nets; giving structure to the goo and blocking light from passing through it.
Eventually via this process the egg white is transformed from a once clear and gooey substance into an opaque gel.
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