Translation

Translation

decoding info.decoding info. Involves the Involves the

interactions of mRNA, interactions of mRNA, tRNA, ribosomes and tRNA, ribosomes and several transciption several transciption factors.factors.

Some ribosomes Some ribosomes attached to attached to membranes (rough membranes (rough endoplasmic endoplasmic reticulum), others not reticulum), others not attached (free attached (free ribosomes) ribosomes)

mRNA leaves the Nucleus and Looks mRNA leaves the Nucleus and Looks for a Ribosomefor a Ribosome

After the code is transcribed the m-After the code is transcribed the m-RNA is further processed: special RNA is further processed: special head and tail regions are added and head and tail regions are added and some parts are spliced out some parts are spliced out

RNA leaves the nucleus and carries RNA leaves the nucleus and carries the code into the cytoplasm, then the code into the cytoplasm, then attaches to a ribosome attaches to a ribosome

TranslationTranslation

The RNA Code is Translated into The RNA Code is Translated into ProteinProtein

Ribosome finds start codon (AUG), Ribosome finds start codon (AUG), then decodes the message, 3 bases then decodes the message, 3 bases at a time at a time

When the ribosome reaches the stop When the ribosome reaches the stop codon the protein is released and the codon the protein is released and the decoding can start over to make decoding can start over to make another protein another protein

mRNA carries the genes.mRNA carries the genes.

The sequence of mRNA The sequence of mRNA strand is complementary strand is complementary to that of DNA.to that of DNA.

Leaves the nuc – cyto to Leaves the nuc – cyto to encounter ribosomes.encounter ribosomes.

Triplet codonTriplet codon specifies a specifies a certain protein in the certain protein in the sequence of amino acidssequence of amino acids

Dictates the production Dictates the production of proteins by ribosomesof proteins by ribosomes..

Translation...Translation... Anticodon is Anticodon is

complementary to the complementary to the codons on mRNA held by codons on mRNA held by H+ bonds.H+ bonds.

Peptidyl transferase Peptidyl transferase catalyses the formation of catalyses the formation of peptide bond between 2 peptide bond between 2 amino acids.amino acids.

Once the amino acids have Once the amino acids have joined, tRNA molecules joined, tRNA molecules are released are released

Base pairing between the Base pairing between the codons of mRNA and the codons of mRNA and the anticodons on tRNA mol anticodons on tRNA mol ensures that the ensures that the transcribed info is transcribed info is translated into the correct translated into the correct sequence of amino acid.sequence of amino acid.

ribosomes move along the mRNA molecule ribosomes move along the mRNA molecule and "read" its sequence 3 nucleotides at a and "read" its sequence 3 nucleotides at a time (codon) from the 5' end to the 3' end.time (codon) from the 5' end to the 3' end.

Each amino acid is specified by the Each amino acid is specified by the mRNA's codon, and then pairs with a mRNA's codon, and then pairs with a sequence of three complementary sequence of three complementary nucleotides carried by a particular tRNA nucleotides carried by a particular tRNA (anticodon).(anticodon).

Polysomes..Polysomes..

Several ribosomes Several ribosomes can attach to an can attach to an mRNA strand mRNA strand simultaneously, simultaneously, forming forming polysomespolysomes..

This speeds up the This speeds up the generation of large generation of large number of number of polypeptides.polypeptides.

SummarySummary

 Process  Where  Major Components  Notes

 Transcription  In the nucleus DNA geneRNA polymerase

 Gene is activated.A copy of the code is made from RNA (m-RNA)m-RNA leaves the nucleus, goes to cytoplasm.

 Translation In the cytoplasm, on the ribosomes

 m-RNARibosomesPeptidyl transferase enzyme Transfer RNAs

 Ribosome decodes the m-RNA and makes the correct protein.

Protein structure

20 a2 serve as subunits20 a2 serve as subunitsEach amino acid has a carboxyl group, Each amino acid has a carboxyl group,

amino group, and a radical group Ramino group, and a radical group RAll bound covalently to a central C.All bound covalently to a central C.R group gives each a2 its chemical R group gives each a2 its chemical

identity.identity.R = CH3 (alanine), CHCH3CH3 = ValineR = CH3 (alanine), CHCH3CH3 = Valine4 main classes = polar (hydrophilic), non 4 main classes = polar (hydrophilic), non

polar (hydrophobic), -ve, +ve charged.polar (hydrophobic), -ve, +ve charged.

structure

PrimaryPrimary SecondarySecondary TertiaryTertiary Quaternary structureQuaternary structure

H+ bondsH+ bonds Disulphide bridgesDisulphide bridges Beta pleated sheetsBeta pleated sheets Hydrophobicc Hydrophobicc

interactionsinteractions