Protein synthesis Flashcards
what happens in RNA processing?
‘5′ methyl guanosine cap added, a poly(A) tail, and splicing of introns’
why is 5’ methyl guanosine cap added?
‘to protect mRNA from degradation adn helps transcript bind to the ribosome for when translation happens’
what does adding the poly A tail do?
helps protect mRNA from degradation and extends life of mRNA
how can variants of a protein be produced?
alternative splicing (controls exons that stay after splicing)
how are eukaryotes different from prokaryotes?
eukaryotes are monocistronic
prokaryotes are polycistronic
what does polycistronic mean?
one mRNA can code for multiple different proteins
how is alternative splicing made possible?
making different splice sites available for splicing machines with the use of RNA binding protein
what does RNA splicing also allow for?
the switch between producing functional and non-functional proteins
what is regulation of decay and translation controlled by?
untranslated regions of mRNA
what is mRNA specific translation regulation controlled by?
‘sequence elements localized in both the 5’ and the 3’ untranslated region (UTR)’
what are mRNA specific decay rates controlled by?
by sequence elements in the 3’ untranslated region
what happens during translation?
the mRNA contains the code
the tRNA carries specific amino acids and binds to complementary codon
ribosomal RNA links the amino acids together
what is required for peptide synthesis?
Initiation, elongation, and termination factors
what is ATP used for?
amino acetyl-tRNA synthetase reaction
what does specificity of a genetic code mean?
the same codon codes for the same amino acid
what does universality of a genetic code mean?
code is virtually universal
what does degeneracy of a genetic code mean?
more than one codons code for the same amino acid
what does non-overlapping and comma-less of a genetic code mean?
‘code read form a fixed starting point as continuous sequence of bases’
what are the 3 main steps of protein synthesis?
initiation, elongation, termination
what is initiation?
‘finding the start codon of an mRNA and putting the first aminoacyl tRNA with the start codon in the P site of the ribosome’
what is elongation?
‘transfer of the growing peptide chain to a new aminoacyl tRNA and moving this new peptidyl tRNA into the P site, putting the next codon in the A site’
what is termination?
‘recognition of the presence of a stop codon in the A site, cleavage of the protein off the peptidyl-tRNA and dissociation of the ribosome from the mRNA’
difference between eukaryotic and prokaryotic protein synthesis?
‘prokaryotes:
are polycistronic
start codon is formylated methionine
target for antibiotics
eukaryotes:
are monocistronic
initiation requires at least 10 factors
ribosomes on endoplasmic reticulum (RER) synthesize proteins that are to be exported from the cell as well as those that are destined to become integrated into plasma, endoplasmic reticulum, or Golgi membranes or incorporated in lysosomes. Cytosolic ribosomes synthesize proteins required in the cytosol itself or destined for the nucleus, mitochondria, and peroxisomes
A single mRNA can have multiple ribosomes (polysome) enable multiple copies of the protein to be made’
what is the A site for?
acceptor tRNA site
what is the P site?
peptidyl tRNA site
what is the E site?
where uncharged tRNA is localised while leaving the ribosome
what are Aminoacyl-tRNA synthetases?
enzymes that attach amino acids to tRNA
how many enzymes for each amino acid is required to attach to tRNA?
20
what is the wobble hypothesis?
tRNA recognises more than one codon for the amino acid
what direction is mRNA code read?
5’ to 3’
what direction is tRNA?
3’ to 5’
what is the flipped orientation of tRNA and mRNA know as?
antiparallel pairing
how is the correct reading frame determined?
by the start codon
what is the coding region?
‘a reading frame encoding a protein’
what happens during initiation?
‘the assembly of the components of the translation system’
what happens with initiation of AUG in eukaryotes?
recognised by tRNA and enters the ribosomal P site and GTP is hydrolyzed to GDP
what happens during elongation?
amino acids added to carboxyl end
then enters the A site
peptidyl transferase catalyzes the formation of peptide bonds
ribosomes moves three nucleotides towards the 3’ end of nucleotide
Uncharged tRNA moves to E site and petidyl-RNA moves to P site
what happens during termination?
one of three codons moves into A site
eukaryotes have single release factor
new polypeptide might go under other modifications the mRNA, tRNA will be recycled to be used again
what happens after translation?
signal sequence has to be removed
what is glycosylation?
addition of sugar moieties to protein forming glycoproteins needed for membrane function
what is phosphorylation of amino acids important for?
to switch enzymes on/off
why is hydroxylation of lysine and proline important for?
stabilizing structure of collagen
why are MicroRNAs important for medicine?
causes loss of mRNA translation
change in miRNA expression will have major effect on gene expression
good biomarkers for when diagnosing
how transcription factors classified?
‘according to the structure of their DNA-binding domains’
what do transcription factors effect?
the number of RNA polymerases binding to DNA
what is the amino-acyl tRNA synthetase reaction?
adding amino acid to tRNA
mRNA stable or degraded?
has imperfect base pairing
what are microRNAs?
‘control protein expression by repression of translation or mRNA degradation’
mRNA degraded?
perfect base pairing
what catalyses formation of ribosome?
peptidyl transferase
how does gene expression increase?
transcription factors bind to enhancers
how are transcription factors classified?
structure of DNA binding domain
what do microbial drugs target in viruses?
‘Inhibition of bacterial thymidine monophosphate synthesis
Inhibition of reverse transcription
Inhibition of bacterial RNA polymerase
block translation by targeting the bacterial ribosome’
what do cancer drugs target in DNA metabolism?
DNA synthesis
antioxidants used to reduce free oxygen radicals in the body
