Now that we have talked about all the steps of gene expression, I want to talk about steps that we can take to regulate this particular process. Specifically, when we're talking about regulating it, we're talking about influencing when it happens and how frequently it happens. First off, let's get at the meaning of gene expression regulation. Really when we're saying gene expression regulation, let's break this down.
We know that gene expression is a term that refers to building a protein from a gene. And we know that regulation refers to dictating how quickly and how frequently something happens. So we kind of put those two things together, then essentially what we're saying is that gene expression regulation regulates how quickly, or let's change it one minute, it regulates when and where proteins are built. Now, good follow-up question is, Why do we need to be able to regulate this? So why are we trying to regulate where built proteins and when they're built?
Well, first thing to keep in mind is that building proteins is energetically expensive, right? It's requiring energy to read the DNA instructions and then make proteins based off of those instructions. So we want a certain amount of efficiency.
Yes, we need to produce proteins as a part of maintaining life. But we don't want to waste energy making proteins we don't need, right? So that's one of the primary reasons why we need to regulate. We don't want to make more. Alright, so it's kind of twofold.
We don't want to make more of a given protein than is necessary, and we don't want to make proteins in locations where they're not going to be used, okay? And really what this boils down to is sort of two primary reasons why we do gene expression regulation. One would be to allow an organism to adapt to its environment. For instance, if you produce in your body a protein called lactase, lactase breaks down the sugar lactose.
And lactose is a sugar that's found in a lot of dairy products, hence you've probably heard of people who are lactose intolerant. They aren't able to break down the lactose sugar, and that's what causes them some unpleasant digestive issues. So using this idea that most people can produce lactase, and that there is a gene that codes for the production of lactase, and lactase breaks down this sugar, it probably makes sense to you that your body does not need to manufacture lactase if you don't consume lactose regularly.
If you haven't consumed the lactose sugar in a while, there is no benefit to your body producing lactase. And therefore, your body would want to regulate gene expression so that that protein isn't produced. That way you're not wasting energy producing an enzyme you don't need at that given time. And then you can also save the amino acids that would be used for that to build other proteins.
Now... Then if you do consume something with lactose in it, then you can start making the lactase again. So it can allow you to adapt to your environment. An example being you can produce digestive enzymes based on what you're consuming so that you're only producing the enzymes for the things that you are consuming. That would be an example.
Another primary reason would be to allow cells in multicellular organisms to specialize. Okay, so we all start off as a single cell and then that cell divides actively and as the cells divide actively They eventually differentiate into different tissues and those different tissues facilitate different functions within the body. Okay now Every single cell in your body has the exact same copy of DNA, but not every cell needs to make the same proteins. For instance, we know that one type of protein that we produce are digestive proteins. We produce a whole suite of digestive proteins for breaking down different substances.
Lactase helps break down lactose. Amylase helps break down starch. And then there's other enzymes for breaking down other types of molecules that you consume so that can be absorbed by your body. And producing those is critical to digestion and acquiring nutrition.
But I think we could all agree that while it's very important that the cells of your stomach and intestines produce these digestive proteins, your eye, the tissues that make up your eye, they don't need to produce digestive enzymes. Actually, it'd probably be really harmful if they did, right? You need different proteins to help you with your eye than you need that's produced in your stomach. But both your stomach cells and your eye cells have instructions for every type of protein that the body is able to produce.
But they need to be selective about which ones are produced in which cells, because not all the cells produce the same functions. So kind of as our example, we'll say your intestine, intestinal. One minute.
So different cells within your body need to be able to selectively produce certain proteins based on what they need to complete their function. They all have a master copy of everything, but they need to be selective about what of that master copy actually gets produced. So there's two discrete examples why we need to be able to regulate when and where proteins are produced. Now the question is, how do we do it?
And this could become a very complex topic that we could spend a lot of time on, but it's a bit more advanced than what we're going to hit on in Bio 100. But what I do want to impress, even though that we're not going to go into the nitty-gritty of all of the ways this can occur, I do want you to know that you can regulate the production of a protein by regulating any step of gene expression. If any of the steps of gene expression halt at that point, you won't produce a protein. So I kind of put an on and off switch at each step here to sort of indicate that as you progress through this process, you can sort of stop the manufacturing. process at any point along the way, right?
Something can occur to stop translation, and if translation doesn't happen, you don't end up with the protein, even if transcription and RNA processing occur. If something is to switch off RNA processing and it halts there, still no protein, even if transcription has happened. So you kind of get the idea that at any step along the way, you could halt the production, and then you would not have the protein at the end.
Now, that being said, the step that is most frequently regulated is transcription. And if you think about it, that makes sense. That's the very first step.
So it makes sense that if you have no intention of producing the protein, probably the simplest thing is to halt at the very first step in the process. There's really no point in undergoing RNA processing if you don't intend to undergo translation and so on and so forth. So although you can, in theory, regulate the production of a protein by manipulating any of the steps of gene expression, the step that is most commonly regulated is transcription.