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RNA Structure 20,540 views

Teacher/Instructor Patrick Roisen
Patrick Roisen

M.Ed., Stanford University
Winner of multiple teaching awards

Patrick has been teaching AP Biology for 14 years and is the winner of multiple teaching awards.

RNA Structure is a single strand composed of nucleotides. Unlike DNA it does not form a double helix shape, but it does contain a series of nitrogenous bases (adenine, uracil, guanine and cytosine). RNA can temporarily form hydrogen bonds between bases of two strands.

When people think about nucleic acids, they typically think of DNA but there's another molecule RNA which is just as important. It's the one that takes the information that's being stored in DNA and sends it out to the cell so that the cell can actually use that info- information. DNA is a really long molecule RNA is typically a shorter molecule but it's just as important as DNA. It's the workers that help carry out some of the information and instructions of the DNA and it's built together much like DNA is so let's take a closer look.

The basic building blocks that make up RNA are nucleotides just like with DNA. Just like DNA it has a phosphate group then gives it a strong negative charge, it has a five carbon sugars sometimes called a pentose and some kind of nitrogen containing base or nitrogenous base. Now one of the differences to bear in mind between DNA and RNA is what is that pentose sugar. Well deoxyribose and ribose are the two sugars. Deoxyribose can you guess which one uses that? You're right! DNA which stands for Deoxyribose Nucleic Acid while RNA Ribonucleic acid uses ribose and if you look at the names they look very similar in fact if I cover up the deoxy I see the word ribose, what does that mean? Well this is ribose notice down here on the second carbon there's an OH group or hydroxyl group for those who are doing Chemistry. If I pull off that oxygen i.e. deduct it, then I deoxygenated this ribose here and look all that's left is the hydrogen so that's the difference between ribose and deoxyribose sugar.

The other difference that you'll see in the structure of the nucleotides is that it uses the same guanine and adenine and cytosine that DNA uses but instead of using thymine uses a particular kind of pyrimidine called uracil. Now to join RNA molecules together it works pretty much the same way as joining DNA molecules together. You take our phosphate and sugar and nitrogenous base i.e. a nucleotide and you bring the phosphate group of the next one in and it joins a phosphate to that sugar and then you extend that and so you windup with a long strand of RNA nucleotides with their bases sticking out with the phosphates and sugars forming the backbone of the strand.

Now you're familiar with this with DNA and you know that DNA often twist up to form the very famous double helix. Well RNA can't do that but because without addition oxygen that's on this carbon right there it tends to make it unstable for long stretches to be in a double helical form. For short portions however you can and the way you can form an RNA to RNA strand or RNA to DNA strand follows the same base pairing rules that DNA does with a lot of twist. Remember that RNA does not use thymine it uses uracil. DNA if we're binding DNA to RNA and we have a RNA adenine here this would have to be a thymine for DNA but if I was making an RNA to RNA where I have an adenine I'll have to use uracil which you'd abbreviate u so if I have my RNa strand here that's a, c, a I follow the standard base pairing rules of a to t or u, g to c so here's the c there's a guanine or g. Here's an a I put a thymine so that's it pretty straight forward it's much like DNA just with those little differences one mnemonic or trick to help you remember the key difference of using uracil instead of thymine is remember what's the abbreviation for uracil, it will be the letter u so just think in your head you are correct and if you are, you are correct.