2.1.3 - Nucleotides and Nucleic Acids Flashcards
What is a nucleotide made of
Pentose monosaccharide
Phosphate Group PO4 2-
Nitrogenous base
Phosphodiester bonds
Formed in a condensation reaction between nucleotides
Phosphate group at 5’ forms covalent bond with hydroxyl group 3’ (H2O)
Forms a long, strong sugar-phosphate backbone with a base attached to each sugar
Difference between ribose and deoxyribose
Deoxyribose doesn’t have an oxygen atom at 2’
Bases
Adenine
Cytosine
Guanine
Thymine/ uracil
Pyrimidines
Smaller bases
Single carbon ring structures
Thymine/ Cytosine
Purine
Larger bases
Double carbon ring structures
Adenine/ Guanine
How do bases pair up
A purine with a pyramidine
Cytosine pairs with guanine - 3 H bonds
Adenine pairs with thymine (uracil - RNA) - 2 H bonds
Structure of DNA
Hydrogen bonding between complementary bases
Double helix composed of two twisted antiparallel strands (phosphate group 5’ - OH 3’/ OH 3’ - phosphate group 5’)
Each strand is a polynucleotide
Why are polynucleotide chains parallel
Complementary base pairing rule:
When a small pyramidine base binds to a larger purine base a constant distance between the DNA ‘backbones’
There will also always be equal amounts of A, T, C, G
Types of RNA
Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)
mRNA
Carries the code held in the genes to the ribosomes where the code is used to manufacture proteins
tRNA
Transports amino acids to the ribosomes
rRNA
Makes up the ribosomes
Phosophorylated nucleotides
ADP and ATP
Contain a pentose sugar (ribose)
A nitrogenous base (adenine)
2/ 3 inorganic phosphates
Semi conservative replication
One old strand and one new strand
Process of semi-conservation replication
Helicase causes the DNA to untwist and breaks the hydrogen bonds between bases
Polynucleotides with exposed bases act as new template for new double strands
Free DNA nucleotide bases pair with their complementary bases - H bonds
DNA polymerase catalyses the formation of phosphodiester bonds between the nucleotides and also checks base pairing
Sugar phosphate backbone reforms
Each new molecule then twists to form it’s double helix