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MODULE 2 - foundations in biology
2.3 - Nucleotides and Nucleic Acids
protein synthesis
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Cards (6)
messenger RNA:
used to transfer
DNA
code from the nucleus to the
ribosome
(
transcription
)
single
stranded
ribose
sugar
contains
uracil
instead of thymine
built up by the
complementary
bases pairing of DNA strand
transfer RNA:
used to decode the
mRNA
sequence into a
protein
(
translation
)
small molecule (approx
80
nucleotides)
single stranded,
clover leaf
shaped with one end slightly longer that can attach to an
amino acid
anti codon
= 3 bases that pair with the
complementary codon
on mRNA
transcription:
helicase
breaks down the
hydrogen bonds
between the bases on a section of DNA
RNA
polymerase moves along the template DNA (
antisense
strand - 3' to 5')
free nucleotides join up with the complementary bases on the antisense strand
C - G, G - C, A - U, T - A
RNA polymerase forms the phosphodiester bonds between the nucleotides
when a stop codon is reached, the chain is terminated and the mRNA strand moves out of the nucleus via nuclear pore
translation:
mRNA
attaches to the
start codon
on the
ribosome
tRNA
with a
complementary anti codon
attaches to the
mRNA
another
tRNA anticodon
binds to the next
mRNA
the
amino acids
on the tRNA molecule are joined by a
peptide bond
the
ribosome
moves along the
mRNA strand
, releasing the
first tRNA
another tRNA is added and the process continues until a
stop codon
is reached
a
polypeptide
is released which forms the
primary
protein structure
start codon -
AUG
(
methionine
)
stop codons =
UAA
,
UGA
or
UAG