Nucleotides Flashcards
Nucleic acids
Information carrying polymers from the monomer nucleotides
Nucleotide general structure
Molecules consisting of a phosphate group bonded to a pentose sugar bonded to a nitrogenous base
What elements are in a nucleotide
Phosphorus
Carbon
Hydrogen
Oxygen
Nitrogen
How are polynucleotides formed?
From the condensation of nucleotide monomers
forming phosphodiester bonds between the phosphate group of one nucleotide and the pentose sugar of the other
Bonds in a polynucleotide name
Phosphodiester bond
How are phosphodiester bonds formed?
The OH group in a phosphate group of one nucleotide and the OH group of a pentose sugar release H2O = condensation
Remaining oxygen forms the bonds between 2 nucleotides
How are polynucleotides broken down?
In a hydrolysis reaction by adding H2O molecules which break the phosphodiester bonds
Examples of polynucleotides
Nucleic acids:
DNA
RNA
DNA structure description summary
2 nucleotides strands
Antiparallel to each other
Hydrogen bonds between complementary base pairs
Bases = A T C G
Double helix
Large molecule
DNA structure: 2 polynucleotide strands meaning
DNA contains 2 polynucleotide strands formed from condensation of nucleotide monomers with phosphodiester bonds between them
DNA structure: anti parallel to each other meaning
The 2 polynucleotide strands run in opposite directions to each other
Where the 5’ carbon is at the top of one strand
Where the 5’ carbon is at the bottom of other strand
DNA structure: hydrogen bonding between strands
Between the complementary base pairs in parallel polynucleotides are hydrogen bonds
DNA structure: complementary base pairs
So a purine base (A and G) always pairs and forms hydrogen bonds to a pyrimidine (T and G respectively)
What does Adenine form hydrogen bonds to and how many?
Thymine
= 2 hydrogen bonds
What does Cytosine form hydrogen bonds to and how many?
Guanine
= 3 hydrogen bonds
DNA structure: long large molecule
Contains a chain of millions and billions of nucleotides
DNA structure: a coiled helix
Wrapped around histone proteins
Proportions of each nucleotide base
The proportion of a base in one strand will be the same as the proportion of the complementary base in the other strand
Why is DNA a long molecule?
So it can store lots of information
Why is DNA a coiled helix?
So it is compact
Why does DNA have a sugar phosphate backbone?
So bases in the middle are protected
Why does DNA have a specific sequence of bases?
So it can code for a specific protein’s amino acid sequence
Why is DNA double stranded?
So it can accurately be replicated with complementary base pairings in semi conservative replication
Why does DNA have weak hydrogen bonds between strands?
So strands can easily be separated when it is being replicated
