蛋白质（protein）是组成人体一切细胞、组织的重要成分。蛋白质在体内转化为脂肪，血液的酸性提高。机体所有重要的组成部分都需要有蛋白质的参与。一般说，蛋白质约占人体全部质量的18%，最重要的还是其与生命现象有关。机体中的每一个细胞和所有重要组成部分都有蛋白质参与。

氨基酸是蛋白质的基本组成单位。它是与生命及与各种形式的生命活动紧密联系在一起的物质。从结构上看，蛋白质具有复杂多样的空间构象，其一级结构是氨基酸的线性排列顺序，而二级结构如α-螺旋、β-折叠等进一步折叠形成三级结构，多个亚基组合则构成四级结构。这种精确的结构赋予了蛋白质特定的功能。

人体内蛋白质的种类很多，性质、功能各异，但都是由20多种氨基酸（Amino acid）按不同比例组合而成的，并在体内不断进行代谢与更新。2025年3月22日，上海交通大学发布Venus系列模型，是全球数据规模最大、功能批注标签最多的蛋白质数据集，为人工智能预测蛋白质结构和掌握蛋白质进化模式提供了宝贵资料。

So far we've covered two of the organic macromolecules carbohydrates and lipids.
到目前为止,我们已经介绍了两种有机大分子:碳水化合物和脂质·
Today we'll be talking about proteins.
今天,我们将讨论蛋白质·
Proteins have many uses.
蛋白质有许多用途·
For example many different proteins are used to form the majority of various body tissues including muscle bone cartilage and hair.
例如,许多不同的蛋白质用于形成大多数不同的身体组织,包括肌肉、骨骼、软骨和头发·
Other proteins form specialized channels in cell membranes to let certain substances into or out of the cell.
其他蛋白质在细胞膜中形成专门的通道,以便让特定物质进入或离开细胞·
Immunoglobulins also known as antibodies are made of proteins.
免疫球蛋白,也叫抗体,是由蛋白质组成的·
They are an important part of the immune system.
它们是免疫系统的重要组成部分·
Antibody proteins label foreign substances in the body so that the immune system can identify and destroy them.
抗体蛋白质标记体内的外来物质,使免疫系统能够识别并摧毁它们·
And all living organisms use regulatory proteins called enzymes to speed up chemical reactions in the body.
所有生物体都使用一种叫做酶的调节蛋白质来加速体内的化学反应·
So what are proteins made of
那么,蛋白质是由什么组成的呢?
Well all proteins are organic macromolecules which means they're large molecules containing the element carbon.
所有蛋白质都是有机大分子,这意味着它们是含有碳元素的大分子·
Like carbohydrates and lipids proteins also contain hydrogen and oxygen.
像碳水化合物和脂质一样,蛋白质也含有氢和氧·
In addition proteins also contain the element nitrogen.
此外,蛋白质还含有氮元素·
So what is the structure of proteins
那么,蛋白质的结构是什么呢?
Well the protein building block or monomer is something called an amino acid molecule.
蛋白质的构建单元或单体叫做氨基酸分子·
Every amino acid has a particular structure.
每种氨基酸都有特定的结构·
They all have the same amino group on one side and a weak acid called a carboxyl group on the other.
它们一侧都有相同的氨基,另一侧有一个叫做羧基的弱酸·
But each amino acid also has a unique side chain called an R group.
但每个氨基酸也有一个独特的侧链,叫做R基团·
It's made up of one or more atoms that distinguish one amino acid from another.
R基团由一个或多个原子组成,这些原子使得每种氨基酸彼此不同·
There are only 20 possible different R groups so that means there are only 20 possible different amino acids.
只有20种可能的R基团,所以意味着只有20种可能的氨基酸·
A protein is created when amino acids chemically bond to each other.
当氨基酸通过化学键结合在一起时,就会形成蛋白质·
The bonds that connect amino acids to make a protein are called peptide bonds.
将氨基酸连接在一起形成蛋白质的键称为肽键·
Small protein molecules are sometimes referred to as protein polymers or peptides.
小的蛋白质分子有时被称为蛋白质聚合物或肽·
Like interconnecting toy blocks amino acids can join together to form even longer protein polymers called polypeptides.
就像连接的玩具积木一样,氨基酸可以连接在一起,形成更长的蛋白质聚合物,称为多肽·
Changing the order of the amino acid sequence or the length of the polypeptide is what creates countless different proteins.
改变氨基酸序列的顺序或多肽的长度,便能创造出无数种不同的蛋白质·
In addition a protein's final folded shape is critical to the function it performs.
此外,蛋白质最终的折叠形状对它所执行的功能至关重要·
Heat or chemicals can change a protein's shape but not its amino acid order.
热量或化学物质可以改变蛋白质的形状,但不能改变它的氨基酸顺序·
However the change in a protein's shape can cause the protein to lose its functionality.
然而,蛋白质形状的改变可能会导致蛋白质失去其功能·
This is called denaturing a protein.
这称为蛋白质变性·
Denaturing is usually not reversible.
变性通常是不可逆的·
An example of denaturing a protein happens when you fry an egg.
变性蛋白质的一个例子就是煎鸡蛋时发生的情况·
Egg whites are pure protein.
蛋白是纯蛋白质·
If you heat an egg the protein in the egg white becomes denatured.
如果加热鸡蛋,蛋白中的蛋白质会发生变性·
You can see the result of this denaturing as the egg white changes from a clear colored liquid to a white colored solid.
你可以看到变性后的结果,蛋白从透明的液体变成白色的固体·
Even after cooling the egg whites' denatured proteins can't change back to their original shape.
即使冷却后,蛋白质变性后的蛋白仍然无法恢复到原来的形状·
So the egg white retains its opaque white color and solid form.
因此,蛋白保持其不透明的白色和固体形态·
To sum up proteins are organic macromolecules containing carbon hydrogen oxygen and nitrogen.
总结一下,蛋白质是含有碳、氢、氧和氮的大分子·
Enzymes most body tissues and many cells in the immune system are all made up of proteins.
酶、大多数体内组织和许多免疫系统细胞都是由蛋白质组成的·
Amino acids are the monomers that make up proteins.
氨基酸是构成蛋白质的单体·
There are only 20 different amino acids.
只有20种不同的氨基酸·
Small protein polymer molecules are often called peptides.
小的蛋白质聚合物分子通常称为肽·
Long chains of amino acids are also a type of protein polymer called polypeptides.
由氨基酸组成的长链也是一种蛋白质聚合物,称为多肽·
Proteins differ in amino acid sequence polypeptide length and folded shape.
蛋白质在氨基酸序列、多肽长度和折叠形状上有所不同·
A protein's folded shape is critical to its function.
蛋白质的折叠形状对其功能至关重要·
内容操作
视频
教程课件
单词卡片