Protein SynthesisProtein SynthesisThe making of proteinsThe making of proteins

Why Do We Need Proteins?

Why Do We Need Proteins? Cell structure – Cellular Cell structure – Cellular

material is 80% material is 80% composed of proteinscomposed of proteins

Cellular processes – Cellular processes – hormones and enzymeshormones and enzymes

Membrane channel Membrane channel proteins for transport of proteins for transport of materials in and out of materials in and out of the cellsthe cells

Cell identificationCell identification To initiate responses.To initiate responses.

NeurotransmittersNeurotransmitters AntibodiesAntibodies Clotting bloodClotting blood PigmentsPigments

etc...etc...

What is a protein What is a protein ? One of the bodies most abundant organic One of the bodies most abundant organic

moleculesmolecules Made up of 20 kinds of amino acidsMade up of 20 kinds of amino acids 100`s of these amino acids are linked 100`s of these amino acids are linked

together in chains to make one protein together in chains to make one protein molecule (polypeptide).molecule (polypeptide).

The sequence of the particular amino acids The sequence of the particular amino acids determines its shape.determines its shape.

The shape of the protein determinesThe shape of the protein determines its particular function.its particular function.

What do we need for protein What do we need for protein synthesis?synthesis?1. 1. DNADNA – the template for making mRNA – the template for making mRNA

through transcription.through transcription.2. 2. RNA RNA – there are three kinds– there are three kinds a) mRNA – messenger RNA.a) mRNA – messenger RNA. Makes and Makes and

takes a copy of the DNA to the cytoplasm takes a copy of the DNA to the cytoplasm where protein is constructed.where protein is constructed.

b) tRNA – transfer RNA.b) tRNA – transfer RNA. The compliment to The compliment to mRNA. Collects the amino acids and brings mRNA. Collects the amino acids and brings them to the ribosomes where polypeptide them to the ribosomes where polypeptide chains are assembled according to the chains are assembled according to the sequence on the mRNA sequence on the mRNA

c) rRNA – ribosomal RNA.c) rRNA – ribosomal RNA. Part of the Part of the ribosome, reads the mRNA and directs the ribosome, reads the mRNA and directs the tRNA tRNA

What do we need for What do we need for protein synthesis? protein synthesis?

3. 3. Amino AcidsAmino Acids – building – building blocks of proteinblocks of protein

4. 4. RibosomesRibosomes - reads the - reads the mRNA, directs the tRNA mRNA, directs the tRNA and creates protiens by and creates protiens by binding the amino acids binding the amino acids together through together through translation.translation.

Each in more detail - Each in more detail - DNADNA

Contains the information to make all the proteins in our body.

Problem: Protein is not made in the nucleus. DNA is too big to leave the nucleus.

How do we get the information from the DNA out of the nucleus to where the protein is made?

Each in more detail - Each in more detail - RNARNARNA: ribonucleic acid.

Smaller than DNA Function: Helps us get DNA information out of the nucleus.

Made in the nucleus but found mostly in the cytoplasm. RNA is used to directly make protein.

Consists of a) single strand of nucleotides b) ribose as the sugar chainc) a phosphate group d) four base pairs (one different from DNA.)

Adenine, guanine, cytocine and Uracil Uracil is a pyrimidine base that replaces thymine and

bonds with adenine| C-G and A-U

RNA Differs from DNARNA Differs from DNA1.1. RNA is smallerRNA is smaller2. RNA has a sugar ribose2. RNA has a sugar ribose

DNA has a sugar deoxyriboseDNA has a sugar deoxyribose3.3. RNA contains the base uracil (U)RNA contains the base uracil (U)

DNA has thymine (T)DNA has thymine (T)4.4. RNA molecule is single-strandedRNA molecule is single-stranded

DNA is double-strandedDNA is double-stranded

Structure of RNAStructure of RNA

Each in more detail - Each in more detail - Amino AcidsAmino Acids

Long chains of amino acids link together to make Long chains of amino acids link together to make a polypeptide chain (protein)a polypeptide chain (protein)

Every amino acid has 5 partsEvery amino acid has 5 parts1.1. Central carbonCentral carbon2.2. Amino groupAmino group3.3. Carboxyl Acid groupCarboxyl Acid group4.4. A single hydrogenA single hydrogen5.5. The ``R`` groupThe ``R`` group – a chain that varies making – a chain that varies making

each of the 20 amino acids uniqueeach of the 20 amino acids uniqueIt is the sequence of nucleic acids on the mRNA It is the sequence of nucleic acids on the mRNA

strand that determines which amino acids go strand that determines which amino acids go together.together.

Let’s Review the Steps we Know

so Far…1. DNA makes a message (DNA makes mRNA)2. Message is sent out into the cytoplasm

(mRNA leaves the nucleus)3. Message arrives at destination (mRNA goes

to ribosome).4. Message is read and directions followed

(tRNA reads the mRNA, a small piece at a time, and gets whatever amino acid that small piece of mRNA says to get).

5. A protein is assembled

Steps of Protein Steps of Protein SynthesisSynthesis

Transcription (writing the “message”)Using DNA to make mRNA which is the messenger that carries code to cytoplasm

Translation (reading the “message”)mRNA and tRNA assemble the amino acid chain. In other words the message is translated into a protein.

TranscriptionTranscriptionTranscriptionTranscription is the process of copying is the process of copying

a sequence of DNA to produce a a sequence of DNA to produce a complementary strand of RNA.complementary strand of RNA.

Occurs in the nucleus.Occurs in the nucleus.Only one gene is transferred into a Only one gene is transferred into a

message, not the entire message, not the entire chromosome.chromosome.

Transcription – Transcription – The making The making of RNAof RNA

RNA polymerase and other proteins RNA polymerase and other proteins form a transcription complex.form a transcription complex.

The transcription complex The transcription complex recognizes the start of a gene and recognizes the start of a gene and unwinds a segment of it.unwinds a segment of it.

start site

nucleotides

transcription complex

Transcription – Transcription – The making The making of RNAof RNA

Nucleotides pair with one strand of the DNA.

RNA polymerase bonds the RNA polymerase bonds the nucleotides together.nucleotides together.

The DNA helix winds again as the The DNA helix winds again as the gene is transcribed.gene is transcribed. DNA

Transcription – Transcription – The making The making of RNAof RNA

The RNA strand detaches from the DNA once the gene is transcribed.

The DNA zips back up and the single strand of RNA is released.

RNA

Transcription is similar to Transcription is similar to ReplicationReplication

Transcription and replication both involve Transcription and replication both involve complex enzymes and complementary base complex enzymes and complementary base pairing.pairing.

The two processes have different end results.The two processes have different end results. Replication copies all the DNA;Replication copies all the DNA;

Transcription copies a segment of Transcription copies a segment of the DNA – one gene.the DNA – one gene.

Replication makes one copy;Replication makes one copy;Transcription can make many copies.Transcription can make many copies.

In replication the pairs stay togetherIn replication the pairs stay togetherIn transcription the copied RNA strand breaks In transcription the copied RNA strand breaks away and the two strands of DNA rebind and away and the two strands of DNA rebind and recoil.recoil.

TranscriptionTranscription

Summing Summing TranscriptionTranscription up in simple termsup in simple terms

1. DNA unzips.2. RNA bases attach to make strand of

mRNA COMPLEMENTARY to DNA (just like when we copied DNA)

3. Only one strand is made (like open-faced sandwich).

4. Use URACIL instead of thymine.5. mRNA leaves nucleus6. DNA zips back up.

Translation Translation – The making of – The making of a proteina protein

Amino acids are coded by mRNA base Amino acids are coded by mRNA base sequences.sequences.

Translation converts mRNA messages Translation converts mRNA messages into polypeptides.into polypeptides.

A codon is a sequence of three A codon is a sequence of three nucleotides that codes for an amino nucleotides that codes for an amino acid.acid.

codon formethionine (Met)

codon forleucine (Leu)

Translation Translation – The making of – The making of a proteina protein

The mRNA joins with the ribosome which The mRNA joins with the ribosome which begins reading the code of nucleic acidsbegins reading the code of nucleic acids

Any portion of the strand Any portion of the strand NOTNOT responsible for coding a polypeptide is responsible for coding a polypeptide is discarded and is called discarded and is called INTRONINTRON

The nucleotide sequence that encodes the The nucleotide sequence that encodes the amino acid sequence (called amino acid sequence (called EXONEXON) is ) is identified by the AUG initiator codon identified by the AUG initiator codon and later followed by a terminator.and later followed by a terminator.

Translation Translation – The making of – The making of a proteina protein

Each codon matches a specific Each codon matches a specific amino acid or function. ***Use the amino acid or function. ***Use the codon to read the chart***codon to read the chart*** Twenty possible Twenty possible

amino acids amino acids three stop codonsthree stop codons one start codon, one start codon,

codes for the amino codes for the amino acid methionine acid methionine

Translation Translation – The making of – The making of a proteina protein

A change in the order in which codons A change in the order in which codons are read changes the resulting protein.are read changes the resulting protein.

Regardless of the organism, codons code Regardless of the organism, codons code for the same amino acid.for the same amino acid.

Translation Translation – The making of – The making of a proteina protein

This is a molecule of messenger RNA.

It was made in the nucleus by transcription from a DNA molecule.

Each set of three nucleotides is a codon.A U G G G C U U A A A G C A G U G C A C G U U

anothercodon

mRNA molecule

Initiator codon

A U G G G C U U A A A G C A G U G C A C G U U

A ribosome either free in the cytoplasm or attached to the rough endoplasmic reticulum connects to the mRNA molecule.ribosome

Translation Translation – The making of – The making of a proteina protein

A transfer RNA molecule arrives.It brings an amino acid to the first three bases (codon) on the mRNA.The three unpaired bases (anticodon) on the tRNA link up with the codon.

A U G G G C U U A A A G C A G U G C A C G U U

Amino acid

tRNA molecule

anticodon

U A C

Translation Translation – The making of – The making of a proteina protein

Met

A U G G G C U U A A A G C A G U G C A C G U U

Another tRNA molecule comes into place, bringing a second amino acid.Its anticodon links up with the second codon on the mRNA.

U A C C C G

Translation Translation – The making of – The making of a proteina protein

Met Gly

A U G G G C U U A A A G C A G U G C A C G U U

A peptide bond forms between the two amino acids.

Peptide bond

C C G U A C

Translation Translation – The making of – The making of a proteina protein

Met Gly

The first tRNA molecule releases its amino acid and moves off into the cytoplasm.

Translation Translation – The making of – The making of a proteina protein

A U G G G C U U A A A G C A G U G C A C G U U C C G U A C

Met Gly

A U G G G C U U A A A G C A G U G C A C G U U C C G

The ribosome moves along the mRNA to the next codon.

Translation Translation – The making of – The making of a proteina protein

Met Gly

A U G G G C U U A A A G C A G U G C A C G U U

Another tRNA molecule brings the next amino acid into place.

C C G A A U

Translation Translation – The making of – The making of a proteina protein

Met Gly Leu

A U G G G C U U A A A G C A G U G C A C G U U

A peptide bond joins the second and third amino acids to form a polypeptide chain.

C C G C C G

Translation Translation – The making of – The making of a proteina protein

Met Gly Leu

A U G G G C U U A A A G C A G U G C A C G U U G U C

A C G

The process continues.The polypeptide chain gets longer. This continues until a terrmination (stop) codon is reached. The polypeptide is complete.

Translation Translation – The making of – The making of a proteina protein

Met Gly Leu Lys Glu

Cys

Summing Summing TranslationTranslation up up in simpler termsin simpler terms

1. mRNA goes to ribosome in cytoplasm (proteins made here!)

2. Exon is identified by the START codon (AUG)3. Intron is discarded4. tRNA reads each codon (three nucleotide set code for

amino acid) and transfers the correct amino acid accordingly.

5. The amino acids are linked together in the codon order.6. tRNA will read the mRNA until it reaches a

TERMINATOR or STOP codon at which point the polypeptide is released from the ribosome.

7. This string of amino acids takes on it’s unique shape - PROTEIN!

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTACCCTGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUGCCTGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUACCCTGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCTGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGAGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCUGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCU GLYGLYGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCU GLYGLYGGA CCUCCUACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCU GLYGLYGGA CCUCCU GGAGGAACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCU GLYGLYGGA CCUCCU GGAGGA PROPROACCTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCU GLYGLYGGA CCUCCU GGAGGA PROPROACC UGGUGG ACCACC TRPTRPTATACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCU GLYGLYGGA CCUCCU GGAGGA PROPROACC UGGUGG ACCACC TRPTRPTAT AUAAUA UAUUAU ILEILEACTACT

Synthesis PracticeSynthesis PracticeDNA DNA

triplettripletmRNA mRNA codoncodon

tRNA tRNA AnticodoAnticodo

nn

Amino Amino AcidAcid

TACTAC AUGAUG UACUAC METMETCCT GGAGGA CCUCCU GLYGLYGGA CCUCCU GGAGGA PROPROACC UGGUGG ACCACC TRPTRPTAT AUAAUA UAUUAU ILEILEACTACT UGAUGA TerminationTermination

Over simplified Protein Over simplified Protein synthesissynthesis

1. DNA unzips2. mRNA made from DNA.3. mRNA leaves nucleus and enters ribosome.4. tRNA reads mRNA from “start” to “stop”5. As tRNA reads mRNA, it brings the correct

amino acids.6. Amino acids are linked together to make a

protein

DNA makes mRNA (complement)mRNA matches up with tRNA (complement)tRNA brings amino acid

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