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Page 1: Protein synthesis

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Page 2: Protein synthesis

DNA contains genes, sequences of nucleotide bases

These Genes code for polypeptides (proteins)

Proteins are used to build cells and do much of the work inside cells

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Page 3: Protein synthesis

Proteins are made of amino acids linked together by peptide bonds

20 different amino acids exist

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Amino acid chains are called polypeptides

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DNA is found inside the nucleus Proteins, however, are made in the cytoplasm of cells by organelles called ribosomes

Ribosomes may be free in the cytosol or attached to the surface of rough ER

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DNA ‘s code must be copiedand taken to the cytosol

In the cytoplasm, this code must be read so amino acidscan be assembled to make polypeptides (proteins)

This process is called PROTEIN SYNTHESIS

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DNA is the MASTER PLAN

RNA is the BLUEPRINT of the

Master Plan

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RNA has a sugar ribose

DNA has a sugar deoxyribose

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

RNA molecule is single-strandedDNA is double-stranded

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DNA

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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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.

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Long Straight chain of Nucleotides

Made in the Nucleus Copies DNA & leaves through nuclear pores

Contains the Nitrogen Bases A, G, C, U ( no T )

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Carries the information for a specific protein

Made up of 500 to 1000 nucleotides long

Sequence of 3 bases called codon

AUG – methionine or start codon

UAA, UAG, or UGA – stop codons

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rRNA is a single strand 100 to 3000 nucleotides long

Globular in shape Made inside the nucleus of a cell

Associates with proteins to form ribosomes

Site of protein Synthesis

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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 stoptranslating

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

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On DNA:A-TC-G

On RNA:A-UC-G

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Clover-leaf shape

Single stranded molecule with attachment site at one end for an amino acid

Opposite end has three nucleotide bases called the anticodon

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amino acidattachment site

U A C

anticodon

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The 3 bases of an anticodon are complementary to the 3 bases of a codon

Example: Codon ACUAnticodon UGA

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UGA

ACU

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DNA

mRNA

tRNA (ribosomes)

Protein

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The production or synthesis of polypeptide chains (proteins)

Two phases:Transcription & Translation

mRNA must be processedbefore it leaves the nucleus of eukaryotic cells

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Nuclear

membrane

Transcription

RNA Processing

Translation

DNA

Pre-mRNA

mRNA

Ribosome

Protein

Eukaryotic Cell

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Translation is the process of decoding the mRNA into a polypeptide chain

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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Made of a large and smallsubunit

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

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

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mRNA transcriptstart codon AUGattaches to the small ribosomalsubunit

Small subunit attaches to large ribosomal subunit

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mRNA transcript

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P

Site

A

Site

Largesubunit

Small subunit

mRNA

A U G C U A C U U C G

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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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mRNA

A U G C U A C U U C G

2-tRNA

G

aa2

A U

A

1-tRNA

U A C

aa1

anticodon

hydrogenbonds codon

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mRNA

A U G C U A C U U C G

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

A U G C U A C U U C G

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

A U G C U A C U U C G

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

A U G C U A C U U C G

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 codon

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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 codon

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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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The end products of protein synthesis is a primary structure of a protein

A sequence of amino acid bonded together by peptide bonds

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aa1

aa2 aa3 aa4aa5

aa200

aa199

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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