Nucleotide Structure & Function Flashcards
What are nucleotides?
Nucleotides are the building blocks of nucleic acids.
What are nucleotides made of?
Nucleotides are made of a nitrogenous base (what differs), a pentose (5-carbon sugar of backbone), and 1 to 3 phosphates (backbone and energy).
What are purines?
Purines are Adenine (A) and Guanine (G) found in both DNA and RNA. (Remember: 2 syllables = 2 rings!)
What are other purine metabolites not found in nucleic acids?
Xanthine, Hypoxanthine, Uric Acid
What are pyrimidines?
Cytosine (C) in both DNA and RNA. Thymine (T) in DNA. Uracil (U) in RNA. (Remember: 1 ring only!)
What is keto-enol tautomerism?
Electrons are floating around due to the double bonds of rings. This allows these isomers to readily interconvert, affecting the fidelity of DNA replication. (Remember: Lactam is keto. Lactim is enol.)
What two types of pentose are found in nucleic acids?
DNA has 2-deoxyribose. RNA has ribose.
Why is RNA less stable than DNA?
Presence of extra OH in ribose makes RNA less stable because the OH will react with highly charged phosphates of the backbone, causing the strand to break.
What is a nucleoside?
Nucleosides are formed by covalently linking a base to the 1’C of a pentose. If that pentose is deoxyribose, it is a deoxyribonucleoside. If that pentose is ribose, it is a ribonucleoside.
What configuration does the nucleoside prefer?
It can be in syn or anti but prefers anti.
When does a nucleoside become a nucleotide?
When 1, 2, or 3 phosphates attach to the pentose (most commonly to the 5’C).
Why are nucleoside di- and tri-phosphates high energy compounds?
They have hydrolytic energy associated with the acid-anhydride bonds.
What is the most important function of nucleotides?
They are precursors of nucleic acids and DNA is the carrier of genetic info.
How do nucleotides function as carriers of energy?
Negative oxygens repel one another so it is energetically favorable to separate but requires energy to cleave bond. Cleaving uses energy to generate a lot more energy.
How do nucleotides function as carriers of specific building blocks?
A phosphate can be cleaved and still attach what is left to something else, then cleave remaining phosphates for energy there also.
What is an example of nucleotides functioning as carriers of energy?
High energy bonds of ATP and GTP
What is an example of nucleotides functioning as carriers of specific building blocks?
UDP-glucose donates sugars in the synthesis of glycogen and glycoproteins.
What is an example of nucleotides functioning as regulatory signals?
Second messengers like cAMP and cGMP mediate the response from certain hormones.
What is an example of nucleotides functioning as methyl donors?
S-Adenosylmethionine (+ ATP) donates methyl groups in certain metabolic pathways.
What is an example of nucleotides functioning as coenzymes in oxidation-reduction reactions?
Niacin, Nicotinamide, or Tryptophan —> NAD+ (+ATP) —> NADP+
Riboflavin (+ ATP) —> Flavin mononucleotide (+ADP)
—> Flavin adenine dinucleotide
What is an example of a nucleotide functioning as a coenzyme in metabolism?
Coenzyme A carries acyl groups (fatty acids) in metabolism.
Why are drugs usually nitrogenous base analogs?
Nucleotides are so important to cell functions that biochemistry can be adjusted by adding something that looks like a nucleotide.
What two drugs are nitrogenous base analogs?
5-Fluorouracil is anti-cancer agent that inhibits replication of cancer cell.
Azidothymidine (AZT) is anti-HIV drug that interrupts replication of HIV virus.
In Keto-Enol Tautomerism, what is Lactam?
Lactam is Uracil in the keto form because the top group is a carbonyl (C=O).
In Keto-Enol Tautomerism, what is Lactim?
Lactim is Uracil in the enol form because the top group is a hydroxyl (OH).
What is the significance of Lactim?
Lactim is less thermodynamically stable so a phoshorylated compound becomes trapped. Changes in its hydrogen bonding pattern can also lead to base pair mismatch mutations.
