2.1.3- nucleotides and nucleic acids Flashcards
describe the structure of a nucleotide
a phosphate group, bonded to a pentose sugar, bonded to an organic nitrogenous base.
what do DNA and RNA stand for
DNA- deoxyribose nucleic acid
RNA- ribonucleic acid
what are the 4 bases for DNA and RNA
DNA: adenine, guanine, cytosine, thymine
RNA: adenine, guanine, cytosine, uracil
what are the two types of organic nitrogenous base, how many rings?
purines: adenine and guanine- double rings
pyrimidines: cytosine and thymine- single rings
how many hydrogens form between
a) adenine and thymine
b) cytosine and guanine
a) 2 H bonds
b) 3 H bonds
what type of bond holds nucleotides together?
phosphodiester bonds between the ribose sugar and the phosphate group, creating the phosphate sugar back bone
describe the 5’ end and the 3’ end
the 5 prime end is at the phosphate end and the 3 prime end is at the deoxyribose sugar end
what is ATP?, When is energy released?
adenosine triphosphate, the universal energy currency. energy is released when pyrophosphate bonds are broken
What is the structure of ATP?
three phosphates, held together by pyrophosphate bonds, one ribose sugar, and the nitrogenous base adenine
what is the process of releasing energy from ATP?
dephosphorylation: a phosphate is released as a pyrophosphate bond is broken in hydrolysis. This results in ADP and a phosphate
why is ATP unstable?
the three negative phosphates next to eachother
outline semi-conservative DNA replication
the DNA double helix unzips as the hydrogen bonds between bases are broken by helicase. Then, free DNA nucleotides will bond with the exposed bases. new hydrogen bonds will form between bases, the nucleotides will join together with the adjacent monomer via phosphodiester bonds.
what does DNA helicase do?
unwinds and separated the two strands of the double helix by moving along the DNA backbones, catalysing reactions that break hydrogen bonds between organic nitrogenous bases, it travels in both directions
what does DNA polymerase do?
synthesises the addition of new nucleotides to the exisiting exposed chain. It can only travel towards the 5’ end of the strand.
explain what is meant by the leading strand, lagging strand, and okazaki fragments
the leading strand is the section from the dna polymerase to the 5’ end. The lagging strand is when the DNA polymerase has to join at intervals, since it can only go towards the 5’ end, forming sections called okazaki fragments.
