Nucleotide Structure, Function, and Metabolism Flashcards
How many hydrogen bonds are formed between adenine and thymine?
2 Hydrogen Bonds
How many hydrogen bonds are formed between guanine and cytosine?
3 Hydrogen Bonds
Why are chromosomes typically found as unwound chromatin within the nucleus and not in the typical perceived chromosome form? Also, in what phase of the cell cycle would this be?
So that the DNA is available for transcription of genes.
During Interphase
Roughly how many nucleotides make up our genome?
3 Billion
What 2 DNA binding proteins are involved in forming chromosomes?
Histones and Non-histone chromosomal proteins
How many more times condensed are chromosomes compared to interphase DNA?
Mitotic chromosomes are condensed 500 times compared to interphase DNA.
What makes up chromatin?
proteins and nuclear DNA
True or False:
Nucleotides are the phosphate ethers of nucleosides.
False - nucleotides are the phosphate esters of nucleosides.
What components make up a nucleotide?
Base - Sugar - Phosphate
What components make up a nucleoside?
Base - Sugar
Which carbon of the sugar is the base attached to in nucleotides, and what type of linkage is this between the nitrogen of the base and carbon of the sugar?
Base is attached to Carbon 1 on the sugar via a Beta-glycosidic linkage.
Which bases have a 2 ring structure?
Purines have a 2 ring structure and they’re:
- adenine (A)
- guanine (G)
- hypoxanthine (I)
- xanthine (X)
Which bases have a 1 ring structure?
Pyrimidines have a 1 ring structure and they’re:
- cytosine (C)
- Uracil (U)
- Thymine (T)
Which carbon is hydrolyzed to make deoxyribose into ribose?
Carbon 2’
What type of bond in ATP links the alpha phosphate group to the ribose sugar?
phosphoric acid ester bond
How is the structure of DNA written and synthesized in respect to sugar attachment?
Written and Synthesized 5’ -> 3’
What type of bond links the beta and gamma phosphate groups to each other and the alpha phosphate group?
phosphoric acid anhydride bonds
Of the listed reactions, rank in order of decreasing entropy:
I) ATP -> ADP + Pi
II) ATP -> AMP + PPi
III) PPi -> Pi + Pi
II > I > III
How many anstrom is in 1 turn of the DNA helix? Also, how many base pairs are there per turn?
34 A
10 base-pairs/turn
Do the bases within the DNA helix point inwards or outwards?
Inwards
DNA exists in multiple forms, but which is the most common and is it hydrated or not?
Mostly B form, which is the hydrated form.
Is DNA replication conservative, non-conservative, or semiconservative?
Semiconservative
**experiment is in book.
Do humans have reverse transcriptase like viruses have?
YES
During the joining of the primer strand at the 5’ to 3’ position, how many inorganic phosphates are cleaved (released)?
2 - PPi
Note that each phosphodiester linkage in the backbone of both DNA and RNA has a negative charge. This negative charge is important in protecting DNA or RNA from?
Negative charge repels nucleophilic species such as hydroxide ion, which are capable of hydrolytically cleaving the phosphodiester linkages of the nucleic acid backbone.
*The absence of the 2’ - hydroxyl group in DNA further increases its resistance to hydrolysis.
In the digestion of RNA, which enzyme cleaves RNA into short RNA oligomers?
Ribonucleases
Which enzyme cleaves the phosphdiester bond of either DNA oligomers or RNA oligomers into nucleoside monophosphates (NMPs) or dexoynucleoside monophosphates (dNMPs)?
Phosphodiesterases
Which enzymes convert NMPs and dNMPs in to nucleosides and deoxynucleosides?
Nucleotidases
What enzyme removes ribose or deoxyribose from its base, resulting in pyrimidines or purines and ribose or deoxyribose sugars?
Nucleosidases
The formation of which molecule in purine synthesis is the committed step of the reaction?
phosphoribosyl amine
What are the two salvage enzymes in purine synthesis?
1) hypoxanthine guanine phosphoribosyl transferase
2) adenine phosphoribosyl transferase
What sources provide the ring atoms in purine bases?
CO2 Gln Gly Asp N10-formyl THF
During purine synthesis, which amino acid contributes carbons 4 and 5, along with the 7th nitrogen?
Glycine
List the different purine bases.
adenine
guanine
hypoxanthine
xanthine
What is phosphoribosyl pyrophosphate (PRPP) synthesized from?
ribose phosphate and ATP
What molecule is a central constituent of nucleotide metabolism?
PRPP
*phosphoribosyl pyrophosphate
