蛋白质(protein)

为数众多的有机化合物，生物化学作用所需的复杂氨基酸聚合物。蛋白质中出现的氨基酸共有二十种，数百个到数千个单位串连起来。有效的蛋白质具有三层重要结构：一级结构（氨基酸序列）由基因决定；二级结构（几何形状，通常是螺旋）由氨基酸之间或内部共价键的角度来决定；三级结构（环状或折叠的整体形状）由氢键与氨基酸侧链来决定。三级结构具有突起、裂缝或囊穴的球形或片状，掌握活动的关键。蛋白质有单纯蛋白质（仅含氨基酸）与接合蛋白质（参阅conjugation），接合对象通常是饮食中少量需求的维生素或金属。血红蛋白是接合蛋白质。蛋白质会与醣类（醣蛋白）、磷（磷蛋白）或硫（硫蛋白）共价连结。构造上的蛋白质是胶原蛋白与角蛋白。几乎都是蛋白质。生物其他的活性蛋白质包括激素（如胰岛素、促肾上腺皮质激素、生长激素）；输送蛋白质携带物质通过细胞膜或到身体不同的部位；还有抗体。蛋白质在工业上有黏着剂、塑胶与纤维等用途，不过大多还是用於食品。

English version：

protein

Any of numerous organic compounds, complex polymers of amino acids needed for biochemical processes. Twenty different amino acids can occur in proteins, in chains of hundreds to thousands of units. An active protein has three important levels of structure: primary (the amino acid sequence), determined by the genes; secondary (the geometric shape, often a helix), determined by the angles of the covalent bonds between (peptide bonds) and within amino acids; and tertiary (the looped and folded overall shape), determined by the hydrogen bonds (see hydrogen bonding) between amino-acid side chains. The tertiary structure, globular or sheetlike with ridges, crevices, or pockets, holds the key to an enzyme's activity. Some proteins are simple (amino acids only), some conjugated (see conjugation) to other groups, often vitamins or metals needed in tiny amounts in the diet. Hemoglobin is a conjugated protein. Proteins may be covalently linked to sugars (glyco-proteins), phosphorus (phospho-proteins), or sulfur (sulfo-proteins). Structural proteins include collagen and keratin. Almost all enzymes are proteins. Other biologically active proteins include hormones (e.g., insulin, ACTH, growth hormone); transport proteins, which carry substances across membranes or to different parts of the body; and antibodies. Proteins have industrial uses in adhesives, plastics, and fibers, but most uses are in foods.

参考文章

• 仙桃蛋白质粉与红桃方片的加工利用果树园艺
• 雏鸡蛋白质的合理添加鸡
• 蛋鸡日粮中蛋白质的标准鸡
• 母猪之能量与蛋白质需求猪
• 怎样解决日粮中蛋白质的来源?鸡
• 奶牛常用的蛋白质饲料有哪些？牛
• 雏鸡蛋白质饲料的科学添加方法鸡
• 养猪巧用蛋白质猪
• 猪的常用饲料-蛋白质饲料-（3）单细胞蛋白质饲料猪
• 寒冷天减少高蛋白质饲料喂量预防猪尿酸盐沉积症猪