DNA structure Flashcards
Nucleotides
monomers that form the basis of the nucleic acids DNA & RNA
pentose sugar of DNA
deoxyribose
pentose sugar of RNA
ribose
Bases
4
thymine (T) and cytosine (C) and uracil, pyrimidines
adenine and guanine, purines
adenine
NH2
guanine
O
thymine
H3C
cytosine
NH2
uracil
O
Formation of nucleotides
phosphoric acid joins nucleotide forming phosphodiester bond between OH grp of the acid and OH group og C5 of sugar
nucleotide is created
How are polynucleotides formed?
The nucleotides join up between the phosphate group of one nucleotide and the
sugar of another nucleotide via a condensation reaction.
C5 of pentose, C3 of pentose
polynucleotide chain
additional nucleotides join by further phosphodiester bonds
that chain of sugars and phosphate is called sugar-phosphate backbone
breakdown of polynucleotide
hydrolysis
The structure of DNA
2 polynucleotide strands joined together to form a double-helix shape through H bonds between bases
complementary base pairings
anti-parallel
equal ratio of pyrimidines to purines
Adenosine Triphosphate
contains a sugar (ribose), a base (adenine) and three phosphate groups.
Breaking down ATP
bonds between these phosphate groups are unstable, easily broken
hydrolysis
phosphorylation
The addition of an inorganic phosphate group to a molecule like ADP
How is ATP suited to energy transfer?
Small and soluble – moves into and out of cells easily
Releases energy in small quantities (which prevents energy wastage)
Has an unstable phosphate bond (which is easily broken)
Easily regenerated (ADP → ATP)
RNA
Short sections of DNA are transcribed into similarly short messenger RNA (mRNA) molecules.
How do RNA nucleotides differ to DNA nucleotides?
ribose instead of deoxyribose
thymine instead of uracil
RNA polymers small enough to leave nucleus and travel to ribosomes
after protein synthesis, RNA molecules are degraded in the cytoplasm, recycled
