Bio 111 lecture 15

Translation is when info in a(n) ____ is translated into a(n) _______.

mRNA, protein

what are the three components necessary for protein synthesis/translation?

mRNA that contains a genetic code

ribosomes

transfer RNAs(tRNAs)

what is the genetic code?

a series of codons on an mRNA

what is a codon?

a sequence of 3 nucleotides

what are the possible functions of a codon?

specify an amino acid

signal translation start/stop

why is it important for codons to signal start and stop of translation?

because mRNAs have 5’ and 3’ untranslated regions

how many different codons are there?

64

is the genetic code universal in all organisms?

yes nearly

why is the genetic code degenerate/redundant?

because it has 64 codons and only 20 amino acids, so some amino acids have more than one codon

how many start codons does the genetic code have?

one

how many stop codons does the genetic code have?

three

what is the start codon?

AUG → Met

what are ribosomes?

enzyme complexes that translate info in mRNAs into proteins(carry out protein synthesis/translation)

what are the two subunits of a ribosome?

large ribosomal subunit

small ribosomal subunit

what is each subunit of a ribosome made up of?

ribosomal proteins and ribosomal RNAs

which subunit is responsible for positioning of the mRNA?

small

what subunit is responsible for binding tRNAs

both large and small

what subunit is responsible for peptide bond formation?

large

what subunit is responsible for recognition of stop codon and protein release?

large

what does release factor signal to release?

the end protein of translation

what are ribozymes(rRNAs)?

RNA molecules that catalyze reactions

what do tRNA molecules do?

carry amino acids to the ribosome

does an uncharged tRNA molecule have an amino acid attached?

no

does a charged tRNA molecule have an amino acid attached?

yes

what is number one?

acceptor stem

what is this a picture of?

tRNA

what is number three?

anticodon loop

what binds to the acceptor stem of tRNA?

amino acid

the anticodon associates with the codon through __________?

complementary base pairing

what type of bond is formed between the acceptor stem and amino acid?

aminoacyl

what do aminoacyl-tRNA synthetase (aaRS) enzymes bind to?

an amino acid

an ATP

an uncharged tRNA

how many different aaRS enzymes are there?

20(one for each AA)

what are the three phases of translation?

initiation

elongation

termination

what happens during initiation?

assembly of the ribosome/mRNA/initiator-tRNA

what happens during elongation?

starts at the start codon, AAs are added until the stop codon

what happens during termination?

the new protein is released and the ribosome complex dissolves

what are the steps of prokaryotic initiation?

initiator and tRNA bind to the start codon

large subunit joins

what are the steps of eukaryotic initiation?

small subunit and initiator tRNA bind to mRNA 5’ cap

complex scans for start codon on the mRNA

large subunit joins