Our next macromolecule is to think about the DNA and RNA. We've already talked about the sugars, but we also need to talk about the nucleotides. Unlike humans and other eukaryotes, prokaryotes can actually build their own nucleotides. We have the purines and the pyrimidines, and if you've not seen this acronym before, it's a good one to remember.
So angels, angels. are pure and have two wings. Now if we change that out for this, A and G, so adenine and guanine are purines and have two rings.
So what we're looking at over here is adenine and guanine, they're purines and they have one and two rings. and pyrimidines over here include all the others so thymine cytosine and uracil and they have one ring so our purines we're going to start with those what i want you to kind of get from this picture here is that these organisms build their nucleotides from different pieces from different sources so we can see here that the amino group of aspartate gives us this particular nitrogen the formal group here from folic acid which is going to be very very important so this is the one i want you to know this is critical for formation of these particular purines this is going to give us this carbon and this carbon and i don't even need to know which carbons it is it's just giving us the formal group gives us these particular um carbons you can see glutamine here gives us an amide nitrogen and those will eventually build up into our purine And similar over here, we also gain parts of our pyrimidines from other sources. I'm not going to ask you to know more than that.
Again, in biochemistry, you'll probably have a little bit more, but know that they come from multiple sources and then are constructed within the bacterial cell. Lipids are our last macromolecule that we're going to discuss. And lipids, remember, form our membrane.
Now... In this, we're going to particularly talk about our fatty acid synthesis. So fatty acid synthesis occurs when we add two carbons to a skeleton from a three carbon molecule or what's called malonate. So here we have malonate and malonate has one, two, three carbons right here.
So this has three carbons and this one has two carbons. and we add these two together so instead of making five carbons we now have four carbons here we have one two three and four and this fifth carbon is lost here as carbon dioxide so for each molecule that's added one molecule of carbon dioxide is released now the interesting thing about this is we'll continue this process as we can see here all the way around this so we'll add in Another three carbon, we'll lose one. We go from six to being eight. We'll add in another three carbon.
We'll go to being a 10 carbon molecule, but we'll lose one carbon again. So this molecule will add on, but the length of the molecule depends on the temperature at which the organism grows. So short fatty acid chains tend to be favored in low temperature.
It keeps the organism more stable, keeps that membrane more fluid, whereas high temperatures tend to form longer chains. And that, again, keeps that chain fluid, but not too fluid. Once we construct these fatty acids, then they're attached to the glycerol to form our lipids. So that's all we're going to talk about for biosynthesis.
There is so much more we could talk about, but we're just going to concentrate on those four examples. of our macros.