chapter 3- nucleic acids Flashcards
what are 2 examples of nucleic acids
DNA and RNA
what are nucleic acids composed of
monomers called nucleotides
what are the subunits of a nucleotide molecule and how are they joined
a pentose sugar attached to a phosphate and a nitrogenous base. they are joined by covalent bonds but the phosphate one is an ester
what is different about the nitrogenous bases on DNA and RNA
DNA nitrogenous bases are A, T, C, G and RNA bases are A, U, C, G. thymine is replaced with uracil
what are the essential ideas for translation
mRNA is translated into an amino acid sequence
it depends on the complementary base pairs between codons and anticodons
what are the purines
guanine and adenine
are there always equal amounts of adenine and guanine
no
what are the pyrimidines
cytosine
thymine
uracil
how do purines differ from pyrimidines (structurally)
purines have 2 rings comtaining nitrogen whereas pyrimidines only have 1
how many hydrogen bonds join A to T
2 hydrogen bonds
how many hydrogen bonds join G to C
3 hydrogen bonds
a purine will always pair with a pyrimidine what does this accommodate
as purine has 2 nitrogen containing rings and pyrimidines only have 1, when the bases pair they will always be 3 across
where is rna found
in the cytoplasm
why cant dna pass through the dna envelope
because it is too large (long and double stranded)
where do nucleotides that make up dna and rna exist
freely in the nucleus
how do polynucleotides form
via a condensation reaction between the 5 carbon phosphate group of one nucleotide and the 3 carbon hydroxyl group on the sugar of another join the two together.
A phosphodiester linkage is formed between two pentose sugars (2 covalent bonds) (linking adjacent nucleotides)
what is the importance of complementary base pairings
always the same distance between each pair of bases.
ensures faithful dna replication and high fidelity of replication =accurate copy
what does bi-directional mean
a mechanism that allows dna replication to proceed in opposite directions on the two strands due to the antiparallel nature of the strands
in translation the ribosomes bind to, move how? and until…
the mRNA and moves along the molecule in a 5’-3’ direction until it reaches the codon
the mRNA is read how many codons at a time
1 codon at a time
tRNA anticodons are what so they can what
are complementary to the codons on mRNA so they align.
each tRNA molecule carries
a specific amino acid
what is the end steps of translation
ribosomes catalyse the formation of peptide bonds between the adjacent amino acids via condensation reactions, the ribosomes moves along the mRNA strand synthesising a polypeptide chain until i reaches the stop codon, the polypeptide is then released
what are the 5 chemical elements that make up nucleic acids
carbon, hydrogen , nitrogen, oxygen and phosphorus
