Английский язык: english for masters of chemistry
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- Бұл бет үшін навигация:
- 3. Apples Turning Brown .
- 4. Crying and Onions .
- 5. Stain Removers
| 2. Color of Meat. There are two types of meat: red and white. Red meat contains a highly
pigmented protein called myoglobin that stores oxygen in the muscle cells. More the myoglobin in the cells, the redder is the meat. However, as meat is heated, the proteins break down and shrink in size. When the interior of the meat reaches 170° F, hemichrome (a tan colored compound) levels rise, and the myoglobin becomes metmyoglobin, which gives well- done meat its brown-gray shade. White meat contains glycogen, which has a translucent "glassy" quality when it is raw. When it's cooked, the proteins recombine, or coagulate, and the meat becomes opaque and whitish. 3. Apples Turning Brown. Apples contain an enzyme called polyphenol oxidase (PPO), also known as tyrosinase. Cutting an apple exposes its cells to the atmospheric oxygen and oxidizes the phenolic compounds present in apples. This is called the enzymatic browning that turns a cut apple brown. In addition to apples, enzymatic browning is also evident in bananas, pears, avocados and even potatoes. 4. Crying and Onions. When you cut an onion you break the cells that form the layers in an onion, thus releasing an enzyme alliinase that reacts with a sulfur-containing compound known as 'prensco', which is also released while cutting. This reaction results in the formation of 1-propenyl sulfenic acid. This acid is further converted to propanethiol S-oxide, a volatile sulfur compound, by the enzyme LF-synthase (meaning lachrymatory factor synthesizing enzyme). This gas, known as the lachrymatory factor (crying factor), reacts with the water in 74 our eyes to form sulfuric acid causing a burning sensation in your eyes and indicating the tear gland to secrete tears. 5. Stain Removers. Soap is formed by the reaction between an alkali and a fatty acid. This produces a molecule with one hydrophilic (water-loving) and one lipophilic (fat-loving) ends. The lipophilic ends stick to oil, grease or dirt. These get engulfed in the soap and are washed away with a fresh stream of water, leaving a clean surface behind. This is just a physical reaction that takes place. Soap and stain removers act as emulsifiers which allow oil and water to mix and so the oily mixtures and difficult stains on body and clothes can be removed after application of soap, stain removers and water. жүктеу/скачать 4.51 Mb. Достарыңызбен бөлісу:
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