MCAT Nucleotides and Nucleic Acids Flashcards
What are the functions of nucleotides?
They store genetic information, participate in oxidation-reduction, and are used in thermodynamically unstable reactions.
What is the general structure of nucleotides?
They have a sugar ( ribose or deoxyribose) liked to a nitrogenous base via a glycosidic bond and contain at least one phosphate via phosphodiester bond.
What are the purines?
Purines is adenine and guanine.
What are the pyrimidines?
Pyrimidines is cytosine, thymine, and uracil
How are nucleotides stabilized?
Through hydrogen bonding
Hydrogen donors has H while hydrogen acceptors has lone pairs.
Tautomerization
The movement of a proton ( accompanied with a change in double bond), This is a chemical modification that can cause incorrect base pairing.
- Adenine and cytosine contains an amino group that can donate a proton to the ring creating an imino group.
- guanine, thymine, and uracil are lactams which can undergo tautomerization to become lactims.
This can disrupt H bonding because it converts hydrogen acceptors to donors and acceptors to donors.
It happens in physiological pH but the amino and lactam forms predominate.
Deamination
Adenine, guanine, and cytosine contains an amine. When this is replaced with a carbonyl it’s called deamination.
Deamination of cytosine turns it into uracil which can easily be detected in DNA since uracil is only found in RNA.
Describe methylation
Cytosine can be methylated which is a way to control gene expression.
When a methylated cytosine it demethylated it becomes thymine.
Nucleosides
Formed with a sugar (ribose or deoxyribose) is bonded to a nitrogenous base.
- Carbon 1 is bonded to the nitrogenous base for pyrimidines. Carbon 9 is bonded to nitrogenous base for purines.
What is it called when adenine, guanine, cytosine, thymine, and uracil is bonded to ribose?
adenosine, guanosine, cytodine, thymidine, uridine.
What does the nucleotides become when they’re bonded to deoxyribose
deoxyadenosine, deoxyguanosine, deoxycytidine, deoxythymidine, deoxyuridine.
What turns a nucleoside into a nucleotide?
The 5’ carbon is bonded to phosphate via a phosphodiester bond. The phosphates are bonded to each other via phosphoanhydride bonds.
How do we classify nucleotides?
By the number of phosphates it has.
1- nucleotide monophosphate ( NMP)
2- NDP
3- NTP
If deoxyribose is thus sugar you put a “d” in front of it.
1- dNMP
2- dNDP
3-dNTP
What are the biological roles that nucleotides play?
- Nucleotides hold genetic information in the form of DNA or RNA.
- Nucleotides play a role in metabolic functions such as ATP
- Nucleotides can be involved in enzyme regulation
