RNA and the Origins of Life - Video Tutorials & Practice Problems

Properties of RNA

Okay so in this topic we're gonna talk about RNA and the origins of life. So uh this video is gonna focus mainly on the properties of RNA. That suggests that it potentially came before other things like DNA and protein. So the reason that we think are in a became before DNA and protein, it's because it has sort of unique properties that suggest it predated them. So what are these properties? All one? And then we talked about some of these before is that RNA can fold into complex three D. Structures. So we can't just have these linear strings of RNA in order to be able to form sort of the complex structures or chemical reactions that were needed for life to form. But RNA has the ability to form into three D structures suggesting that it could form these structures that have functions um that allow for life to form. And one of these functions is through uh sort of RNA is called Ribas seems which are these complex you know, three D. RNA molecules that actually have abilities to catalyze chemical reactions. Um And so when these structures form, I mean obviously today they're really complex. But you can imagine sort of in the origins of life early earth that these aren't a molecule. Three D. Structures were simple but they helped speed up small chemical reactions and um those reactions are super necessary for life and um that is one of the properties that allows us to think you know RNA was likely um formed before DNA because DNA doesn't have these properties. And then also another final property that we want to talk about is that the shape of RNA. So the shape of these three D. Structures actually can change when bound to small molecules or other RNA. S. So the fact that these three D. Structures aren't entirely rigid allows for RNA to respond to signals in the environment. Been through sort of confirmation all changes of its structure. And so um the fact that our naked fall into these structures can catalyze chemical reactions and can respond to its environment um sort of you know independent of life, suggests that these were the foundations that led to the creation or the formation of life on earth. So um just to get an idea so this is actually a rib design. Um so that is a RNA molecule that can catalyze chemical reactions and you can see that it's complex, it's three D. But it also has the ability to respond to different small molecules or something that come in and bind and then can change its structure. And so these are really important properties of RNA. That suggests that it predated DNA and protein. So let's move on

Life Requirements

So if RNA is going to be, you know, we're gonna say, okay, RNA was the molecule that was responsible for the origination of life, it has to meet certain requirements. So the first requirement that it has to me is it has to be able to store information because things like heredity is like we have to be able to pass on genetic information to our offspring um in order to continue life. So RNA has to have the ability to do this. And so um today obviously it doesn't do this for the most part because um it's so complex today. But you can imagine in the sort of in the beginnings it did have the ability to do this because it forms these poly nucleotide chains that store information can be replicated. Um but also have the ability in certain rivers seems to guide its own formation and replication. And so DNA doesn't have these properties. And RNA does. Now the second requirement for life is that life requires the ability to speed up or otherwise known as catalyze chemical reactions. Certain reactions are necessary for life and these sort of life sustaining reactions really occur too slowly to have happened by chance. So RNA has the ability to catalyze and speed up these reactions. And so are in a has this ability. Um and so today we see this, we have rib designs or things like our RNA and ribosomes which are really responsible for speeding up chemical reactions. And um as our days were thought to be present before proteins we can see things like ribosomes as a remnant of evolution because RNA was likely driving that process and still drives it today. So if we kind of look at RNA as a storage molecule, we've seen these before, we have these, you know, the single stranded RNA molecule that has basis and the order of these bases determined um its structure, its function. Um and that's really important for being an origin of life molecule. So let's move on.

Evolution of RNA

So now let's talk about the evolution of the RNA world. So there were likely a three phases in the history of life. So the first one is actually going to be called the pre RNA world. And so um this world kind of had an RNA like molecule before RNA was actually created and it had the ability to catalyze reactions. Um so there was probably some kind of preliminary race like structure that was much simpler than RNA, but eventually over time it became and transitioned into RNA and probably or likely actually catalyzed the formation of the first RNA molecules. And they believe that this world may have even arisen before the first cell. So these are kind of just, you know, chemical reactions that are occurring before there were even cells present on earth, but eventually RNA became the dominant force. And so when the RNA world was really in full swing, chemical reactions likely occurred in compartments and that was in order to separate them because sometimes chemical reactions need to be separated from other molecules in order to occur. And so um during this time the first cell likely had this sort of small or very simple membrane by layer. And inside of it, the only thing inside of it likely was catalytic RNA that could do chemical reactions. So you have chemical reactions on the outside and the chemical reactions inside this membrane by layer. And you can barely consider this a cell, but it was, it has a membrane by layer and sort of things going on inside this is very early. And so because the RNA molecules existed inside the membrane by layer, it could evolve separately from the chemical reactions that are going on outside the environment. Um And that's really important and likely ledge the development of more complex cells. And so at this time RNA molecules would have to be able to self replicate themselves because they were separated from the environment. So the only way that they would be able to continue is to be able to replicate their own selves. But eventually this transition to D. N. A. Occurred and um today we know that D. N. A. Is more stable than RNA and it acts as a better sort of store of genetic information because it's more stable. But the problem is is of course deoxyribonucleic is more complicated to make than the Revo sugar found in RNA. But today we don't really care about that or doesn't really matter because we have all these complex proteins and stuff that can handle the formation of deoxyribonucleic and so eventually it became the permanent information storage molecule. So those are the kind of the three phases of this evolution process that began with the pre RNA world, led to the RNA world and then led to what we know now, which is what we're living in currently is the D. N. A world. So let's move on

Choose all of the following properties that indicates RNA pre-dated both DNA and proteins.

• A. RNA has the ability to catalyze chemical reactions
• B. RNA is extremely stable
• C. RNA can fold into complex 3D shapes
• D. RNA can store information
• E. RNA is more complicated to make than DNA

Ribozymes have catalytic functions because of why?

• A. They bind to proteins, which allow them to exert their effect on other molecules
• B. They are translated into proteins
• C. They can fold into 3D conformations that act similarly to proteins
• D. None of the above