TRANSLATION Flashcards
What is the function of a protein?
perform structural and catalytic functions
what is translation?
ribosomes read the genetic message in the mRNA and produce a protein according to the message’s introduction which uses a substantial amount of energy
where does translation occur?
occurs in the ribosomes in which mRNA attaches itself to ribosomes resulting in polypeptides which are folded to form proteins
what is mRNA?
carries genetic instructions for protein synthesis from DNA in the nucleus to the ribosomes in the cytoplasm
what happens to mRNA during translation?
it is read according to genetic code which relates to DNA sequence to the amino acid sequence in proteins
what is rRNA?
major component of the ribosomes ; protein synthesis
where is rRNA produced?
synthesized in the nucleolus and shipped out of nucleolus through the nuclear pores to cytoplasm in eukaryotic cells
what does each ribosome have?
1 mRNA and 3 tRNA binding sites
what happens to rRNA during translation?
facilitate the coupling of tRNA anticodon to mRNA codon - APE site
what is tRNA?
brings amino acids to ribosomes for protein synthesis
- each tRNA has 3 bases that make up the anti codon which pairs with the 3 bases of the codon on mRNA during translation
what is the A site?
aminoacyl-tRNA site which holds the tRNA carrying next amino acid to be added to polypeptide chain
what is the P site?
peptidyl-tRNA site which holds the tRNA carrying growing polypeptide chain
what is the E site?
exit side in which empty tRNA leaves ribosome from exit side and attach themselves to amino acids by aminoacyl-tRNA synthetase resulting in tRNA with an amino acid attached to it (charged tRNA/aminoacyl-tRNA)
what can 3 bases do?
3 bases = 1 codon = 1 amino acid
- 64 (4^3) possible outcomes which is more than enough to code for the 20 amino acids
how many codons code for amino acid?
61 codons
what are start codons?
AUG - methionine
what are stop codons?
UGA, UAA, UAG
what happens during initiation?
1) ribosome binding site on mRNA binds to a complementary sequence on small subunit ribosome with the help of proteins knows as initiation factor
2) initiator tRNA brings in the first amino acid ‘methionine’ and binds to mRNAs start codon, AUG
3) large subunit of ribosome binds, placing initiator tRNAs in the P-site
what happens during elongation?
1) incoming tRNAs bind to the codon in the A site via complementary base pairing between anticodon and codon
2) Amino acid in the P site breaks the bond with its tRNA and forms a peptide bond with the amino acid in the A site
3) TRANSLOCATION : ribosomes move down to the next codon on mRNA in the 5’t o 3’ direction as tRNA shifts over one spot towards the 3’ and tRNA will exit from the E site
when does termination happen?
when a stop codon is revealed in A site in which a protein known as release factor enters the A site
what does the release factor do?
promotes hydrolysis of the bond linking the tRNA in the P site with its polypeptide resulting in the polypeptide and tRNAs being released
what happens during termination?
ribosomal subunits, mRNA and protein release factors all separate from one another
what are ribosomes?
PROTEIN FACTORY :
each mRNA molecule is simultaneously translated by many ribosomes, all reducing the mRNA from 5’ to 3’ and synthesizing the polypeptide
DNA to protein
1) sequence of bases in the DNA determines the sequence of amino acids in a protein
2) sequence of amino acids determines a protein’s structure and function
3) small change in DNA may cause a large change in protein
