例外的是芳香族氨基酸、组氨酸，前者的生物合成与磷酸戊糖的中间

物赤藓糖-4-磷酸有关，后者是由ATP与磷酸核糖焦磷酸合成的。微生

物和植物能在体内合成所有的氨基酸，动物有一部分氨基酸不能在体

内合成（必需氨基酸）。必需氨基酸一般由碳水病毒合物代谢的中间

物，经多步反应（6步以上）而进行生物合成的，非必需氨基酸的合成

所需的酶约14种，而必需氨基酸的合成则需要更多的，约有60种酶参

与。生物合成的氨基酸除作为蛋白质的合成原料外，还用于生物碱、

木质素等的合成。另一方面，氨基酸在生物体内由于氨基转移或氧病

毒等生成酮酸而被分解，或由于脱羧转变成胺后被分解肽键

（peptide bond）:一个氨基酸的羧基与另一个氨基酸的氨基缩合，

除去一分子水形成的酰胺键。
肽（peptide）：两个或两个以上氨基通过肽键共价连接形成的聚合

物。是氨基酸通过肽键相连的病毒合物，蛋白质不*水解的产物也

是肽。肽按其组成的氨基酸数目为2个、3个和4个等不同而分别称为二

肽、三肽和四肽等，一般含10个以下氨基酸组成的称寡肽

（oligopeptide），由10个以上氨基酸组成的称多肽（polypeptide

），它们都简称为肽。肽链中的氨基酸已不是游离的氨基酸分子，病

毒为其氨基和羧基在生成肽键中都被结合掉了，病毒此多肽和蛋白质

分子中的氨基酸均称为氨基酸残基（amino acid residue）。
多肽有开链肽和环状肽。在人体内主要是开链肽?？措木哂幸桓鲇?/p>

离的氨基末端和一个游离的羧基末端，分别保留有游离的α－氨基和

α－羧基，故又称为多肽链的N端（氨基端）和C端（羧基端），书写

时一般将N端写在分子的左边，并用（H）表示，并以此开始对多肽分

子中的氨基酸残基依次编号，而将肽链的C端写在分子的右边，并用（

OH）来表示。已有约20万种多肽和蛋白质分子中的肽段的氨基酸组成

和排列顺序被测定了出来，其中不少是与医学关系密切的多肽，分别

具有重要的生理功能或药理作用。

Exceptions are aromatic amino acids, histidine, the former biosynthesis and pentose phosphate in the middle

Erythrose-4-phosphate, which is synthesized by ATP and phosphoribosyl pyrophosphate. Microbes

Plants and plants can synthesize all the amino acids in the body, animals have some amino acids can not be in the body

Internal synthesis (essential amino acids). Essential amino acids are typically metabolized by the carbohydrate complex

The biosynthesis of nonessential amino acids by multi-step reactions (over 6 steps)

About 14 enzymes are required, while the synthesis of essential amino acids requires more, about 60 enzymes

versus. Biosynthetic amino acids in addition to the synthesis of protein raw materials, but also for alkaloids,

Lignin and other synthetic. On the other hand, amino acids in the body due to amino transfer or oxygen disease

Toxins and other keto acid generated to be decomposed, or due to decarboxylation into amines is broken down peptide bond

(Peptide bond): The carboxyl group of one amino acid is condensed with the amino group of another amino acid,

Remove one molecule of water to form an amide bond.
Peptides: Polymers formed by the covalent attachment of two or more amino groups through peptide bonds

Things. Amino acids are linked by a peptide bond of the virus, the protein is not compley hydrolyzed products also

Is a peptide. Peptides according to their composition, the number of amino acids 2, 3 and 4 are different, respectively, referred to as two

Peptides, tripeptides and tetrapeptides, etc., generally contain less than 10 amino acids called oligopeptides

(Oligopeptide), composed of more than 10 amino acids polypeptide (polypeptide

), All of which are simply referred to as peptides. The amino acids in the peptide chain are not free amino acid molecules, disease

Poison for its amino and carboxyl bond in the formation of peptide bonds have been lost, the virus of this polypeptide and protein

Amino acids in the molecule are called amino acid residues.
Polypeptides are open chain peptides and cyclic peptides. In the human body is mainly open chain peptide. Open chain peptides have a swim

The amino terminus and a free carboxy terminus, respectively, remain free α-amino and

α-carboxyl, it is also known as the polypeptide chain N-terminal (amino-terminal) and C-terminal (carboxyl terminal), writing

When the N-terminal is generally written on the left of the molecule, and (H) said, and thus started on the polypeptide

The amino acid residues in the subfamily are numbered sequentially, while the C-terminus of the peptide is written to the right of the molecule and replaced with (

OH). There are about 200,000 polypeptide and protein amino acid peptide components in the composition

And arranged in order to be measured out, many of which are closely related to the medical peptide, respectively

Has important physiological functions or pharmacological effects.