Protein Synthesis

Protein Synthesis Protein Synthesis

Steps:Steps:TRANSCRIPTIONTRANSCRIPTION

DNA unwinds, RNA is made from DNADNA unwinds, RNA is made from DNA

DNA acts as a template for RNADNA acts as a template for RNA

Protein SynthesisProtein Synthesis

mRNA mRNA It is copied from the part of DNA It is copied from the part of DNA called a gene. called a gene. mRNA for hair colormRNA for hair color mRNA for liver enzymesmRNA for liver enzymes mRNA for skin colormRNA for skin color

Read 3 bases at a time (codon)Read 3 bases at a time (codon)

Protein SynthesisProtein Synthesis

mRNA copy moves out of nucleus into mRNA copy moves out of nucleus into cytoplasm.cytoplasm.

Transcription

Protein SynthesisProtein Synthesis

tRNA tRNA

becomes active when amino acids becomes active when amino acids are attached to them.are attached to them.

They carry amino acids to the They carry amino acids to the ribosome.ribosome.

They have the anticodon.They have the anticodon.

Protein SynthesisProtein Synthesis

mRNA attaches to the ribosome in mRNA attaches to the ribosome in cytoplasm. cytoplasm.

A tRNA bonds complementarily with A tRNA bonds complementarily with the mRNA by its anticodon.the mRNA by its anticodon.

TranslationTranslation

A second tRNA bonds with the next codon A second tRNA bonds with the next codon on the mRNA, the amino acid joins onto on the mRNA, the amino acid joins onto the amino acid of the first tRNA making the amino acid of the first tRNA making a peptide bond.a peptide bond.

**peptide bond is a fancy name for a **peptide bond is a fancy name for a covalent bond.covalent bond.Translation

A third tRNA, with the correct A third tRNA, with the correct anticodon, brings a third amino acid anticodon, brings a third amino acid to the mRNA.to the mRNA.

Protein SynthesisProtein Synthesis

The ribosome moves along. The first The ribosome moves along. The first tRNA leaves the ribosome.tRNA leaves the ribosome.

All the rest of the amino acids are All the rest of the amino acids are added. added.

The ribosome moves down the mRNA and The ribosome moves down the mRNA and complimentary tRNA drops off the complimentary tRNA drops off the appropriate amino acid.appropriate amino acid.

Protein Synthesis

Eventually a stop codon is reached on Eventually a stop codon is reached on the mRNA. the mRNA.

There is no anticodon for a stop codonThere is no anticodon for a stop codon

The newly synthesised polypeptide The newly synthesised polypeptide leaves the ribosome.leaves the ribosome.

The mRNA and ribosome come apart.The mRNA and ribosome come apart.

The tRNA, ribosome, and mRNA are all The tRNA, ribosome, and mRNA are all reused to make more of the same reused to make more of the same type of protein. type of protein.

For each gene there is one For each gene there is one polypeptide synthesized. polypeptide synthesized.

So if an organism has 100 genes it So if an organism has 100 genes it has 100 proteins to makehas 100 proteins to make

Overview

Summary