I . DNA & RNA | 1. Chemical structure of nucleotides.... Flashcards
3 types of nucleotides
nucleosidemonophosphate
nucleosidediphosphate
nucleosidetriphosphate
What are the 2 purine bases?
What are the 3 pyrimidine bases?
What does Nucleoside contain?
nucleobase + pentose
What does nucleotide contain?
nucleoside + 1 phosphate
group (at least)
What are Nucleobases?
N-containing heteroaromatic compounds, substituted purine or pyrimidine rings.
Structural features of Purines and pyrimidines
They are nitrogen- containing heterocycles. They contain, in addition to carbon, other (hetero) atoms, such as nitrogen. Their six-atom rings are numbered in opposite direction.
- Pyrimidines: with the clock
- Purines: against the clock
Oxo-enol tautomerism of nucleobases
-> What are Tautomers?
isomers of a compound which differ only in the position of protons (H) and electrons.
- The oxo and amino groups of purines and pyrimidines exhibit ___ (which phenomenon)
oxo-enol and amine-imine tautomerism
oxo-enol and amine-imine tautomerism
-> Physiological conditions favor which forms?
They favor oxo + amino forms
In RNA, the sugar moiety to which the phosphates and purine + pyrimidine bases are attached to ___
is ribose, rather than the 2’ deoxyribose of DNA.
What are Bonds between the phosphate
ester bond, and 2 acid anhydride bonds
Acid anhydride bonds are considered as ___
macroergic bonds (store high energy)
Nucleosides are derivatives of ____
purines and pyrimidines
What is Steric hindrance by the heterocycle?
there is no freedom of rotation about the beta-N-glycosidic bond of nucleosides/nucleotides
2 forms of Heterocyclic N-glycosides
- Heterocyclic N-glycosides exist as syn- and anti-conformers
What are Nucleic acids?
polynucleotides specialized for information storage and transmission. They
are composed of multiple nucleotide units connected by phosphodiester bonds.
Similarity and Difference in primary structures of DNA and RNA
DNA and RNA are linear polymers composed of nucleotides which are linked by phosphodiester bonds
Explain why we read 5’ -> 3’ direction of polynucleotide chains
- In a single chain of DNA, there is a hydroxyl group at 3’ end and a phosphate group at 5’ end on their terminal sugars
- The phosphodiester bonds link adjacent nucleotides
- By this convention (+ synthesis proceeds 5’ to 3’), the polynucleotide sequences are written and read in the 5’ to 3’ directionality
What is The secondary (3D) structure of polypeptide chains?
Nucleic acid secondary structure is the basepairing interactions within a single nucleic acid polymer or between two polymers.
What is The secondary (3D) structure of DNA?
1/ DNA is a right-handed double helix with 2 polynucleotides chained running antiparallel to each other.
2/ The two sugar phosphate backbones are on the outside of the double helix, whereas the bases project into the interior
3/ Base-bair complementary:
- A-T base pair: 2 hydrogen bonds
- G-C base pair: 3 hydrogen bonds (stronger
interaction)
=> A consequence of the size, shape, and chemical composition of the bases
4/ Hydrogen bonds -> main contributor stability of the double helix
Hydrophobic and van der Waal interactions further stabilize
How is the phosphodiester bond formed?
A bond consisting of 2 phosphoester bonds, one on the 5’ side of the phosphate and another on the 3’ side
In DNA and RNA, the phosphodiester bond is the linkage between the 3’ carbon atom of one sugar molecule and the 5’ carbon atom of another, deoxyribose in DNA and ribose in RNA.
describe the secondary structure of RNA?
Stem-loops, hairpins and other secondary structures can form by base pairing between distant complementary segments of an RNA molecule
- In stem-loops, the single-stranded loop between the base-paired helical stem maybe hundreds or event thousands of nucleotides long
- in hairpins, the short turn may contain as few as 4 nucleotides
Base pairing:
A - U: 2 H-bonds
G - C : 3 H-bonds
