蛋白质

蛋白质是四种基本类型的组织形式之一c molecules. Now when I teach them in my class kids will ask me "so what do proteins do?" And it's actually a lot easier for me to explain but they don't do because proteins are used for so many different things in your body. For example, they form a lot of different structures. A protein called keratin for example makes up your hair. A protein called collagen makes up your ligments and tendons and lips.

有很多由蛋白质组成的不同事物。抗体是针对外国入侵者的免疫系统的主要武器之一，它们是由蛋白质制成的。胰岛素等激素是由蛋白质制成的，然后是细胞的化学工人酶制成的，这些是蛋白质的蛋白质。因此，他们几乎可以在牢房中做任何事情以及您想做的一切。

构成蛋白质的单体称为氨基酸。它们结合在一起，形成称为多肽的长链。现在，这些长氨基酸的链条以非常复杂的方式折叠在一起，复杂的结构使科学家有一段时间的问题。但是，让我们从更仔细地看待什么是氨基酸。现在，所有氨基酸和大约二十种在自然界中都有四个基本部分。中心部分称为α碳，该碳含有氢，然后是所有其他侧基。这里的该组称为氨基组，它由带有几个氢的氮组成。一些教科书取决于所吸引的pH，将显示三个教科书，但我选择只做两个。在这里，我们有羧基，该羧基将酸性质量赋予氨基酸，因为该C双键是羧酸。就像您在化学方面学到的所有酸一样，有时氢会掉落，因此您有时可能会看到这种氧气旁边有一些负面符号。 Up here you see the R group. That doesn't mean that it's a pirate R. That instead is just a place holder used to represent the different side groups that give each amino acid its individual qualities. For example here we see the amino acid called alanine and you'll see that its R group is a methyl group, a carbon with three hydrogens attached to it while over here cysteine has the same amino, amino, carboxyl, carboxyl group but instead of the methyl group it's got a C, double H and then a sulphur over the hydrogen attached to it. That gives it very different chemical and structural properties than the methyl group here. Phenylalanine and glutamic acid also share very different qualities based on their R group.

Now when scientists first started studying proteins, a protein basically will have this kind of structure and if I explain, asked you "so go ahead and describe this to me." You'll sit there go "what! It just looks like a tangled mess" and some respects that's what proteins are, tangled masses. And it's too hard for early scientists to figure it out. It's much like if you hand a kindergartner a big novel and say "so, tell me, what are the themes that run through The Lord of the Rings?" They'll throw up their hands up in failure. So instead scientists started off at the most basic level and they came up with something called "primary structure" and then once they started understanding that, they went to secondary structure and tertiary structure, the third level of structure. Now we're getting much better and much able, much more able to understand the structure of proteins. We even learnt about something called quaternary structure which is how multiple proteins work together.

但是，让我们看一下这个YouTube视频，让我们看看它如何显示所有这些不同的级别的组合。因此，我将继续进行全屏。因此，在这里我们看到一堆氨基酸。现在，它们结合在一起，这是氨基酸的序列，称为主要结构。现在，由于他们的R组，他们都开始相互互动，因此我们的长链将开始形成这些怪异的小弯曲部分，并在那里曲折的部分。现在，科学家不喜欢将事物称为弯曲的零件和曲折的零件，因此他们将其命名为Alpha Helix和Beta百褶床单。我将继续在这里暂停视频，并向您展示一些有助于展示这一点的模型。在这里，这显示了一个α螺旋，它只是一条长长的氨基酸链相互连接，但由于R组和氨基酸链的其他部分之间的氢键，它开始形成这种扭曲的结构。您在曾经学习过DNA之前就听说过螺旋，因为它具有双链曲折形状，称为双螺旋。

Now in the video you saw these bendy parts that were running in parallel. That's called a "beta pleated sheet" and that's what we see. So we have again one long chain but it gets bent up because of the structural properties of carbon to form this up and down up and down sheet shape called a beta pleated sheet. The pleated part refers to the, how it buckles up and down like that, kind of like pleats on a pair of pants. So both of those qualities are determined by primarily the hydrogen bonding of the various R groups in the amino acid chain. So let's restart up the video and see now how we take these small regions of structure, the secondary structure and we have all sorts of other interactions, more hydrogen bonding and covalent bonding between different parts of the chain to form the three dimensional shape. Now, a lot of proteins are done then but some proteins have additional chains attached to them and in very specific ways which is called the "quaternary" or fourth level of structure and that's a protein.