PROTEIN SYNTHESIS PROTEIN SYNTHESIS Introduction and Overview.

PROTEIN PROTEIN

SYNTHESISSYNTHESIS Introduction and Introduction and

OverviewOverview

Protein SynthesisProtein SynthesisHow DNA directs how proteins are How DNA directs how proteins are

mademade

The variety of The variety of life on earth is life on earth is

due to due to different different proteins.proteins.

Protein SynthesisProtein Synthesis

You are different You are different from the people from the people

around you around you because your because your proteins are proteins are different.different.


Your hair, Your hair, muscles fibres in muscles fibres in your skin are all your skin are all

made of proteins.made of proteins.


If you have If you have straight hair, straight hair,

your protein is your protein is slightly different slightly different to someone who to someone who

has curly hairhas curly hair


Proteins are made up of units Proteins are made up of units called amino acidscalled amino acids

In our examples we will use a few In our examples we will use a few amino acids to represent a amino acids to represent a protein protein

Proteins are much larger and Proteins are much larger and have more that 50 amino acidshave more that 50 amino acids


Proteins are made up of units called Proteins are made up of units called amino acids.amino acids.

Amino acids join together to make Amino acids join together to make proteins.proteins.

Protein SynthesisProtein SynthesisProteins differ from each other by the Proteins differ from each other by the type (different shapes) and sequence type (different shapes) and sequence (the order in which the shapes occur) of (the order in which the shapes occur) of amino acids.amino acids.

If this is the If this is the protein for protein for straight hairstraight hair

A single A single amino acid amino acid change change results in results in curly haircurly hair


The proteins are different because The proteins are different because the DNA for curly and straight hair the DNA for curly and straight hair is different.is different.

There is a THREE letter DNA code There is a THREE letter DNA code (codon) for each amino acid.(codon) for each amino acid.

Eg. TGG codes forEg. TGG codes for


In this example:In this example:

TAC codes for aTAC codes for a

AAA codes for aAAA codes for a

AGC codes for AGC codes for aa

GGT codes for GGT codes for aa

The code for this aminoThe code for this aminoacid sequence is :acid sequence is :

What is the DNA What is the DNA codecodefor this sequence?for this sequence?

AAA GGT GGTAAA GGT GGT TAC TAC AGC AGC GGT GGT

G

G

C

A

U

U

U

A

A

CC

C

G

T

A

A

A

T

T

GG

G

C

A

T

T

T

A

A

C

Protein Synthesis: Overview of the Protein Synthesis: Overview of the ProcessProcess

DNADNA ProteinProteinRNARNA

makesmakes makesmakes

Protein Synthesis: A closer Protein Synthesis: A closer looklook

Firstly, part of Firstly, part of the DNA is the DNA is copied into copied into

messenger RNA messenger RNA (mRNA)(mRNA)

This is calledThis is calledTRANSCRIPTIONTRANSCRIPTION

The The mRNA mRNA carries carries the message to the message to

make the protein make the protein to the cytoplasm to the cytoplasm and attaches to and attaches to the ribosomethe ribosome


tRNAtRNA collects collects amino acids in the amino acids in the

cytoplasmcytoplasm


TRANSLATION: TRANSLATION: tRNAtRNA brings amino brings amino

acids to the acids to the ribosome which ribosome which link and form link and form

proteinsproteins


Protein SynthesisProtein SynthesisThe Detailed ProcessThe Detailed Process

TRANSCRIPTIONA piece of DNA that codes for a protein is copied into

mRNA

Part of the Part of the DNA DNA

molecule molecule is is

unzipped unzipped by an by an

enzymeenzyme

TTRRAANNSSCCRRIIPPTTIIOONN

DNA DNA separatesseparates


TA

AC

A

AA

G

GC

GT A

C

A

CGCUUUUGU A piece of A piece of

DNA from DNA from one side is one side is copied intocopied into

mRNA


TA

AC

A

AA

G

GC

GT A

C

A

CGCUUUUGU

A U AG U U U U C G C C

mRNAmRNA separates separates from DNAfrom DNA


TA

AC

A

AA

G

GC

GT


TA

AC

A

AA

G

GC

GT


mRNAmRNA moves moves out of the out of the

nucleus to a nucleus to a ribosome in ribosome in

the the cytoplasmcytoplasm

ribosome

A U AG U U U U C G C CAC G C C

mRNAmRNA attaches to a attaches to a ribosome ribosome

TRANSLATION

The ribosome encodes mRNA to form a new

protein

A U AG U U U U C G C CU A C

tRNA brings a specific amino acid which links mRNA

mRNA

tRNA

Amino Acid

A U AG U U U U C G C CU A C

mRNA

tRNA

Amino Acid

mRNA three letter code (codon)

Corresponding tRNA code (anticodon)

The tRNA with its specific amino links to mRNA according to its

specific three letter code

U A CA U AG U U U U C G C C

A A A

tRNA brings in the next amino

acid according to the next mRNA

codon

The amino acids combine

The ribosome moves along the mRNA molecule

exposing the next codon

tRNA moves into the cytoplasm to collect another

amino acid

U A C

A U AG U U U U C G C CA A A A G CA G C

tRNAs bring in another amino acids to extend the protein chain

The process continues as the ribosome moves along mRNA exposing the next codon

A U AG U U U U C G C CA G C G G U

The process continues as the ribosome moves along mRNA exposing the next codon

tRNAs bring in another amino acids to extend the protein chain

A U AG U U U U C G C CG G U

TERMINATION: Ribosome and mRNA separate

NEW “Protein” is formed

In Summary …

T A TC A A A A G C G GDNAmakes

A U AG U U U U C G C CRNA

ProteinProtein

makes

PROTEIN SYNTHESIS PROTEIN SYNTHESIS Introduction and Overview.

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