We're going to say that amino acids are molecules containing an amino group and a carboxyl functional group. In addition to this, they're going to have what's called an R side chain. If we take a look at this image here, we're going to say that this image, we've illuminated this carbon here in purple that represents our alpha carbon. Our alpha carbon is basically in the middle of everything that's going on in terms of our amino acid. Here, this alpha carbon is connected to an amino group here, and then it's also connected to a carboxyl group, so this carboxylic acid group here. In addition to this, this alpha carbon has this R group here. And in this case, also, we're going to say that this alpha carbon has this hydrogen up above. Now here, we're going to say that this is the generic way of writing an alpha amino acid. We're still focusing on the alpha carbon and the groups attached to it.
Now physiological pH is 7.4. In this type of environment, the amino acid takes on another form. In this form, we're going to say that our amino group has gained an H+. And remember, when nitrogen makes 4 bonds, it's positively charged. So now we have NH3+ here. Within this environment, it's slightly basic, basic enough that our carboxylic acid has lost its H+ group, so now it's a carboxylate anion. We still have our R group here. R is just a placeholder for a hydrogen, a carbon, a larger more complicated group necessary. We'll talk about that later on. In addition to this, the alpha carbon is still connected to this H. We're going to say that this form that the amino acid takes within physiological pH is called your zwitterion ion. Your zwitterion ion is the molecule bearing 2 groups of opposite charges. So in this case, we're talking about the amino group which is positive and the carboxylate anion which is negative.
Now, here we're going to say that there are 20 alpha amino acids, and these are your standard amino acids. And they make up the building blocks of proteins and living organisms. So this R group, when it comes to alpha amino acids, the standard forms, there are 20 different types of R groups, giving us these 20 different types of amino acids. Now we're going to say they possess different R groups attached to the alpha carbon. Alright. So, when it comes to our amino acid, remember, we have our alpha carbon in the middle attached to our carboxyl group, our amino group, and our R group, and then we have that hydrogen. So as we delve deeper into understanding amino acids, we'll see how this becomes more complex.
