Before we get into talking about the four groups of macromolecules, there's one other kind of idea I want to talk about that's going to pop up as we talk about the macromolecules, and that is functional groups. So here's the idea with functional groups. We have 118 different elements that we talked about with the periodic table that we theoretically have to use to build any given molecule.
And when it comes to living organisms, we said that really of the 118, 25 are primarily what we're using. to make the molecules that make up living organisms, including these macromolecules we're going to talk about. So since there's only really 25 elements that we're primarily using to build these structures, it's likely that we're going to see similar arrangements of atoms in different kinds of molecules. It's the same concept even with just letters in our alphabet, right?
So we have 26 letters in the English alphabet. Right, we have 26 letters and we have hundreds of thousands of different words. So with hundreds of thousands of different words and only 26 different building blocks, there are times where you see the same combination of letters in different words.
For instance, tricycle and triangle. These both have the same prefix, right? They both have tri at the beginning.
And that... prefix, even though the two words are different, the prefix means the same, right? Those three arrangements of letters has the same meaning in these two different words that have different meaning.
A tricycle is a type of bike that has three wheels. A triangle is a shape that has three sides. So the tri part is in reference to three.
That's sort of a good analogy to what functional groups are like. Functional groups are a piece of the larger molecule that has the same arrangement. and is seen in many different types of molecules.
Okay, and like the prefixes having the same meaning, functional groups have the same overall function or properties in each one of the molecules that they make up. So it can be really beneficial to know what the property of that functional group is because then it can give you a sense of how that part of the molecule will act. Likewise, it's beneficial to know prefixes and suffixes because even if you don't know what the entire word means, you at least know what that portion often means when found in other words. So a functional group is a combination of atoms that is found in many molecules.
So examples of some functional groups that are common are listed off here to the right. In the image, when you see the letter R, that is in reference to where it would attach to the larger molecule. So it would kind of be like me writing try with a dash, right? The try is the prefix, the dash is where it would attach to the rest of the word. In this case, the...
Abbreviations for the elements are listed and then the R is kind of like the dash where it would attach to the rest of the molecule. Okay, so for instance, one functional group that we are gonna see a lot is a phosphate group. I'll kind of highlight this one because we're gonna see it multiple times.
A phosphate group, okay, here's where it would attach to the larger molecule, whatever it's in, is a phosphorus atom that's bonded to four different oxygens. One of those bonds is a double bond, and then two of the four oxygens have a hydrogen bonded to it. So anytime you see this arrangement of atoms, that's that's called a phosphate group. And in terms of properties, phosphate groups have a negative charge associated with them because they have a tendency to release one of the hydrogen ions into solution.
So they're also considered to be an acid because when you add hydrogen ions to a solution, you're increasing the hydrogen ion concentration, and so that's an acidic property. And this is how the phosphate group is functional in other types of molecules. So again, kind of like the prefix, even if you don't have a great sense of the entire molecule and how it's going to function, this piece, if you know that the phosphate group has these properties, you have a sense for how that portion of the molecule will function. So I don't expect you necessarily to memorize these. but they will pop up from time to time, and I will use the functional group name to describe them.
So if I say a phosphate group, or a carboxyl group, or a carbonyl group, or a methyl group, just keep in mind that's in reference to a functional group, a specific arrangement of atoms that has a specified property and that might very well pop up in different kinds of molecules.