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
Structure of RNA
A single polynucleotide strand
Nucleotide structure is:
a phosphate molecule bonded to a ribose sugar and nitrogenous base
The pentose sugar in RNA is?
Ribose
What are the nitrogenous bases in RNA?
Adenine and Uracil
Cytosine and Guanine
DNA vs RNA: pentose sugar
DNA has deoxyribose
RNA has ribose
DNA vs RNA: strands
DNA is a double helix structure of 2 polynucleotide strands
RNA is a single strand polynucleotide strand
DNA vs RNA: bases
DNA has Thymine, Guanine, Cytosine, Adenine
RNA has Uracil, Guanine, Cytosine, Adenine
DNA vs RNA: complementary base pairings
DNA has complementary base pairs: A and T, C and G with hydrogen bonds between
mRNA is single stranded so no base pairs
tRNA has Hydrogen bonds
DNA vs RNA: sugar phosphate backbone
DNA is stable due to having a sugar phosphate on either side to protect bases in middle
mRNA is more unstable because only has one sugar phosphate backbone
DNA vs RNA: length
DNA is a long molecule with billions of nucleotides
RNA is a short molecule with thousands of nucleotides
DNA vs RNA: function
DNA stores genetic information
RNA creates proteins and has 3 types:
messenger (carry genetic code for translation)
transfer (carry amino acids in translation)
ribosomal
mRNA vs tRNA
mRNA is linear molecule whereas tRNA has a clover leaf shape
mRNA has no H bonds whereas tRNA does
mRNA has no anticodon region whereas tRNA does
mRNA has no amino acid binding site whereas tRNA does
tRNA function
Carry amino acids to the complementary codon (by comp base pairs to its anticodon region) during translation
Why do the nitrogenous bases in DNA provide stability?
The hydrogen bonds between complementary pairs in the DNA strands hold the molecule together
Many hydrogen bonds together provide strength
Why can some organisms have very similar proportions of bases in DNA but be different organisms?
Because it is the sequence of bases that matter so organisms have different base sequence
In their different genes
So synthesises a different polypeptide with different amino acid sequences
When would the proportion of complementary bases not being equal suggest?
The bases aren’t complementary so suggests the DNA molecule is single stranded
