2.1.3 protein synthesis Flashcards
(10 cards)
why must transcription take place
DNA is too big to leave the nuclear pore
can’t risk damaging it
how is the DNA molecule unzipped
DNA helicase breaks the H bonds between the bases
separates the section of DNA containing the gene that will be copied
what is the difference between the sense and antisense strand
sense strand = has code for protein; goes from C5 to C3
antisense strand = complementary to sense strand; acts as template to produce mRNA w/ protein code; runs from C3 to C5
how does the mRNA strand form
free RNA nucleotides will bond to complementary bases on antisense strand
RNA polymerase catalyses formation of phosphodiester bonds
double helix reforms behind enzyme
when does the mRNA stop coding
when a stop codon is reached
the mRNA will detach from the template
splicing occurs for eukaryotic mRNA to remove introns
how does translation begin
the mRNA leaves the nucleus
it binds to the small subunit on a ribosome
holds it in place
explain the role of tRNA in translation
tRNA have an AA attachment site at top + an anticodon at bottom
anticodon = complementary to mRNA codon
the anticodon binds to the mRNA + forms H bonds (starts at start codon)
when another tRNA enters the ribosome + binds the AA will form peptide bonds
how many tRNA moles does the ribosome hold
can hold up to 2
ribosome shifts down the mRNA
once the AA bond the first tRNA is released and a third can enter
this continues until a stop codon is reached
what happens once the stop codon is reached in translation
the polypeptide chain is released
it is in its primary structure
folding occurs into secondary, tertiary, quarternary structure (depending on AA present)
enter golgi app for modification
which pre-mRNA contains introns + describe what they are
eukaryotic mRNA has introns
prokaryotic mRNA does not
introns = non coding part of DNA
