This lecture continues the classification and structural configuration of the most important amino acids, including lysine, arginine, histidine, and others. It also includes some of the important reactions of amino acids. Cysteine can dimerize to form cysteine, which has a disulfide bond. Amino acids with aromatic groups can generally absorb UV light, making them easier to identify and analyze. Some proteins also have derivative or modified amino acids such as hydroxyl lysine, which has an extra OH group, and r-carboxy glutamate, which is relatively uncommon but has an extra carboxyl (COO⁻) group.
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This is called arginine and it is Arg, and its single letter designation is an R.0157
Notice, on the alpha carbon, you've got 2 methylene groups, and then you have a nitrogen with a hydrogen, then you have another carbon; and then you have on this carbon, you have an NH2 group, an amino group, and you have a protonated amino group.0167
And again, I encourage you to double check these structures.0581
I am not using a figure and running through it.0584
I'm actually drawing these things out, so please confirm that I have actually drawn them correctly.0588
We are all human; we all make mistakes, so by all means, this is actually a great way for you to actually look at a figure in your book; and make sure that I'm actually drawing it out correctly, and I'm matching the right amino acid, with the right name and the right three-letter symbol and the right single-letter symbol, rather than just taking my word for it.0593
Now, let's go on and talk a little bit about these.0858
Some things you should know about the amino acids, there are thousands of things that you should know about the amino acids, but we don't have all the time in world.0861
We'll worry about that as you go on in your biomedical career, but a couple of things that you should keep in mind as we begin our discussion of proteins and amino acids: you should know about the amino acids.0874
So, let's go ahead and do C, COO-, +NH3, this is going to be CH2, this is going to be S, this is going to be S, this is going to be CH2; this is going to be another alpha carbon - yes, that's right – this is going to be COO-,COO-, this is going to be +NH3, and there is an H, S, S.0965
This right here, this is called the disulfide bond.1053
Profoundly important - we'll be talking about this in a couple of lessons - a disulfide bond.1058
This is how long chains of amino acids, actually they bend and fold, and when a cysteine in one part of the protein chain, and there is a cysteine on another part of the protein chain, when they tend to come together, they end up actually forming a covalent bond, this disulfide bonds.1065
So, what you have is this loop, and there might be other places where it's connected.1084
Disulfide bond is very, very important in the overall structure of a protein.1088
Now, 2H+ + 2 electrons, or you can think about it as 2 hydrogen atoms, either way.1093
Some are derived from common amino acids and they do show up in proteins, but are modified after the protein has been synthesized- after protein synthesis.1280
In other words, there are some uncommon amino acids that you do find in proteins, but they're not incorporated while the protein is being built one amino acid at a time, strung together as beads on a string.1311
They use these particular uncommon amino acids.1324
The protein is built using the 20 common amino acids, and then after that, there is a modification.1329
There is something added; there is something subtracted to a particular amino acid residue, to a particular amino acid on the protein chain.1337
I'm just going to list a couple of them, just so you know.1345
And again, you'll find more on your book and I would certainly urge you to take a look at them just structurally.1348
Authors: Albert Lehninger, David L. Nelson, Michael M. Cox
Publisher: W. H. Freeman
Lehninger Principles of Biochemistry has been a classroom favourite since its first edition. It is the classic introduction to biochemistry that brings clarity and coherence to an often unwieldy discipline, a textbook on the field's classic core, always made fresh by combining the field's definitive advances with an admirable ability to reach students. This book includes major advances in Biochemistry.
Authors: Jeremy M. Berg, John L. Tymoczko, Lubert Stryer
Publisher: W. H. Freeman
With a balance of topic coverage and depth this updated third edition covers the subject of biochemistry, and reflects the advances made in this field since the second edition published in 1981. It emphasizes the growing interrelatedness of molecular biology and biochemistry, and acquaints one with experimental methods of both disciplines.