MCAT Mnemonics: Purines and Pyrimidines

Ken Tao is the MedSchoolCoach expert on MCAT, and uses clever word plays to convey how purines are as pure as gold, and how pyrimidines prove that pyramids are sharp, they cut!

Full Transcription

Hey, welcome back to another MCAT Mnemonic Monday. My name is Ken and I’m an MCAT expert with MedSchoolCoach. Today, we have a biology mnemonic for you and it’s on purines and pyrimidines.

These are nitrogenous bases that are part of the structure of nucleotides. Up here on the board, you can see we’ve drawn the structures of all five nitrogenous bases. And for the MCAT, you do need to know which ones are the purines and which ones are the pyrimidines.

So here we can see that adenine and guanine with their two ring structures are the purines, and cytosine, thymine, uracil with the one ring structure are the pyrimidines.

The mnemonic that we can use to help memorize these is: For purines – Pure as Gold. So purines, we have the word “pure” in there, so pure as gold tells us that the purines are adenine and in guanine. For pyrimidines, we have the word “pyramid” in pyrimidines. So we say that “Pyramids,” they have this triangular structure, they’re sharp, so they cut, and cut tells us that the pyrimidines are cytosine, uracil, and thymine.

And as an extra bonus, when you think about purines because they are pure, their structure is intact. So the purines are gonna have to rings in their structure.

When you think about the pyrimidines, because they’re sharp and they cut, they’ve been cut so they only have one ring.

So that’s an extra bonus to help you remember that purines have two rings and pyrimidines only have one ring.