食品专业英语 LESSON 4 Amino Acids And Proteins.docxVIP

食品专业英语 LESSON 4 Amino Acids And ProteinsProteins are molecules of great size, complexity, and diversity. They are the source of dietary amino acids, both essential and nonessential, that are used for growth, maintenance, and the general well-being of man. These macromolecules, characterized by their nitrogen contents, are involved in many vital processes intricately associated with all living matter. In mammals and many internal organs are largely composed of proteins. Mineral matter of bone is held together by collagenous protein. Skin, the protective covering of the body, often accounts for about 10% of the total body protein. Some protein function as biocatalysts (enzymes and hormones) to regulate chemical reactions within the body. Fundamental life process, such as growth, digestion and metabolism, excretion, conversion of chemical energy into mechanical work, etc, are controlled by enzymes and hormones. Blood plasma proteins and hemoglobin regulate the osmotic pressure and PH of certain body fluids. Proteins are necessary for immunology reactions. Antibodies, modified plasma globulin proteins, defend against the invasion of foreign substances of microorganisms that can cause various diseases, food allergies result when certain ingested proteins cause an apparent modification in the defense mechanism. This leads to a variety of painful, and occasionally drastic, conditions in certain individuals. Food shortages exist in many areas of the world, and they are likely to become more acute and widespread as the worlds population increases, providing第四课氨基酸和蛋白质 蛋白质错综复杂、多种多样的大分子物质，是食物必须氨基酸和非必须氨基酸的来源。 人体利用这些氨基酸以满足生长发育、修复组织和维持正常健康生活的要求。这些大分子以 含氮为其特征，参与了许多与各种有生命物质有复杂联系的生命过程。在包括人类在内的哺 乳动物中，蛋白质起着机体改造成分的作用，肌肉和许多体内器官主要由蛋白质构成。骨骼 中的矿物质靠胶原蛋白得以保持在一起。机体的保护层一皮肤中的蛋白质通常占机体蛋白质 总量的10%的左右。 有些蛋白质有生物催化剂（酶和激素）的作用，以调节体内的化学反响。基本的生命过 程如生长、消化、代谢、排泄、化学能转变成机械功等等都受酶和激素的控制。某些体液的 渗透压和pH值受制于血浆蛋白和血红蛋白。蛋白质对免疫反响是必不可少的。抗体（改性 的血浆球蛋白能引起疾病的外来杂质和微生物的入侵。当某些摄入的蛋白质使防御机制产生 明显的变化时，便发生人体的生物过敏。这就导致某些个体身上出现各种各样的疾病，且