Protein Synthesis - Weebly · End Product –The Protein! •The end products of protein synthesis is a primary structure of a protein •A sequence of amino acid bonded together

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PROTEIN SYNTHESIS

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DNA and

Genes

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Roles of RNA and DNA

• DNA is the MASTER PLAN

• RNA is the BLUEPRINT of the

Master Plancopyright cmassengale

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RNA Differs from DNA

• RNA has a sugar ribose

DNA has a sugar deoxyribose


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Other Differences

• RNA contains the base uracil (U)DNA has thymine (T)

• RNA molecule is single-strandedDNA is double-stranded

DNAcopyright cmassengale

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Structure of RNA


Central Dogma of Biology

DNA codes for RNA which guides

the synthesis of proteins!7

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. Three Types of RNA

• Messenger RNA (mRNA) copies DNA’s code & carries the genetic information to the ribosomes

• Ribosomal RNA (rRNA), along with protein, makes up the ribosomes

• Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized


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amino acidattachment site

UA C

anticodon

mRNA

rRNA

tRNA

Central Dogma of Biology

DNA codes for RNA which guides

the synthesis of proteins!10

Step 1

TRANSCRIPTION IS HAPPENING AT THE SAME TIME AS DNA

REPLICATION!

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Transcription - 1

• A portion of the DNA molecule unzips

• Recall: DNA helicase is the enzyme responsible for this!


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Transcription - 2

• RNA polymerase joins RNA nucleotides using the DNA strand as a template

• This strand of DNA read by the RNA is the “template strand” read in the 3’ to 5’

• This new strand of RNA is the mRNA strand made in the 5’ to 3’ direction

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Transcription - 3

• The mRNA strand is released through nuclear pores (exits the nucleus) and the DNA strand rejoins

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RNA Polymerase


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mRNA Processing

• After the DNA is transcribed into RNA, editing must be done to the nucleotide chain to make the RNA functional

• Introns, non-functional segments of DNA are snipped out of the chain


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mRNA Editing

• Exons, segments of DNA that code for proteins, are then rejoined by the enzyme ligase

• The newly processed mRNA can then leave the nucleus


19CAP TailNew Transcript

Result of Transcription


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mRNA Transcript - 4

•mRNA leaves the nucleus through its pores and goes to the ribosomes


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The Genetic Code

• A codon designates an amino acid

• An amino acid may have more than one codon

• There are 20 amino acids, but 64 possible codons

• Some codons tell the ribosome to stop translating


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The Genetic Code

•Use the code by reading from the center to the outside•Example: AUG codes for Methionine


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Name the Amino Acids

• GGG?

• UCA?

• CAU?

• GCA?

• AAA?


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Remember the Complementary Bases

On DNA:A-TC-G

On RNA:A-UC-G


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Question:

What would be the complementary RNA strand for the following DNA sequence?

DNA 5’-GCGTATG-3’


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Answer:

•DNA 5’-GCGTATG-3’

•RNA 3’-CGCAUAC-5’


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Translation

• Translation is the process of decoding the mRNA into a polypeptide chain to create proteins

• Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins


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Transcription

Translation


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Ribosomes

• Composed of rRNA (40%)and proteins (60%)

• Have two sites for tRNA attachment --- P and A


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Step 1- Initiation

• mRNA transcriptstart codon AUGattaches to the small ribosomalsubunit

• Small subunit attaches to large ribosomal subunit

mRNA transcriptcopyright cmassengale

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Ribosomes

P

Site

A

Site

Largesubunit

Small subunit

mRNA

A U G C U A C U U C G


Step 2 - Elongation• As ribosome moves, two tRNA with

their amino acids move into site A and P of the ribosome

• Peptide bonds join the amino acids

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Initiation

mRNA


2-tRNA

G

aa2

A U

A

1-tRNA

U A C

aa1

anticodon

hydrogenbonds codon


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1-tRNA 2-tRNA

U A C G

aa1 aa2

A U

A

anticodon

hydrogen

bonds codon

peptide bond

3-tRNA

G A A

aa3

Elongation


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mRNA


1-tRNA

2-tRNA

U A C

G

aa1

aa2

A U

A

peptide bond

3-tRNA

G A A

aa3

Ribosomes move over one codon

(leaves)


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mRNA


2-tRNA

G

aa1

aa2

A U

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U


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mRNA


2-tRNA

G

aa1aa2

A U

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

(leaves)

Ribosomes move over one codoncopyright cmassengale

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mRNA

G C U A C U U C G

aa1aa2

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

U G A

5-tRNA

aa5


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mRNA

G C U A C U U C G

aa1

aa2

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

U G A

5-tRNA

aa5

Ribosomes move over one codoncopyright cmassengale

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mRNA

A C A U G U

aa1

aa2

U

primary

structure

of a protein

aa3

200-tRNA

aa4

U A G

aa5

C U

aa200

aa199

terminator

or stop

codon

Termination


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End Product –The Protein!

• The end products of protein synthesis is a primary structureof a protein

• A sequence of amino acidbonded together by peptide bonds

aa1

aa2 aa3 aa4aa5

aa200

aa199


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Messenger RNA (mRNA)

methionine glycine serine isoleucine glycine alanine stop

codonprotein

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

start

codon

Primary structure of a protein

aa1 aa2 aa3 aa4 aa5 aa6

peptide bonds

codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1


Documents

Protein Synthesis - Weebly · End Product –The Protein! •The end products of protein synthesis is a primary structure of a protein •A sequence of amino acid bonded together