Protein SynthesisProtein Synthesis

What is protein synthesis?Is protein synthesis important?

What is RNA?Where is RNA found?

Is RNA similar to DNA?What is translation?

What is Protein Synthesis?

Protein Synthesis*Protein synthesis is the building of proteins following the instructions of DNA

*The instructions of DNA are written by the order of the bases in DNA.

Why is Protein Synthesis Important?

Importance*Proteins make up the structure of an organism AND control all of the organism’s chemical reactions to keep it alive.

3 examples of proteinsHemoglobin

Elastin

Collagen

Proteins

Structure• A protein is made up

of a chain of AMINO ACIDS in a particular order, held together by PEPTIDE BONDS.

Protein Shape Shape• shape of a protein

depends on its function & its order of amino acids

Primary Protein Structure

Secondary Protein Structure

Where does protein synthesis occur?• The DNA never leaves the nucleus because it

is too BIG

• RNA copies the DNA in the nucleus.

• RNA carries the instructions from DNA out to the ribosome.

• The protein is built on the ribosome in the cytoplasm.

DNA is safe in the nucleus

Uses mRNA To send a message to the cytoplasm

Bellringer 11/4/10

1. Based on the picture on the board, where does transcription occur?

2. Where does translation occur?

What is RNA?• RNA (Ribonucleic Acid) *It is the nucleic acid responsible for three

things in protein synthesis:1. copying instructions from DNA2. carrying the instructions for making proteins

to the ribosome3. putting the protein together on the

ribosome.

What is RNA?• What is the sugar in RNA called?

Ribose

• How many strands does RNA have? One

Types of RNA3 Types of RNA1. Messenger RNA (mRNA)2. Transfer RNA (tRNA)3. Ribosomal RNA (rRNA)

Messenger RNA (mRNA) Function: 1. Makes a copy of DNA using RNA bases. 2. Takes the copy to the ribosomes.Codon: group of 3 bases on mRNA.

Types of RNA

Transfer RNA (tRNA)Function:1. carries amino acids to the ribosome that

match up with mRNA to make the protein.2. contains the “ANTICODON” (3 bases that

match up w/codon on mRNA)

Types of RNA

Ribosomal RNA (rRNA)• Major structural part of the ribosome where

protein synthesis occurs.

DNA RNA

Strands 2 1

Sugar Deoxyribose

Ribose

BasesA-TC-G

A-U C-G

Overview of Gene Expression

Steps in Protein Synthesis: TranscriptionLocation: in the nucleusPurpose: to copy the DNA code (order of

bases) onto mRNA.Events:– DNA is unwound and DNA helicase unzips

DNA strand.– RNA polymerase reads the complementary

base and free RNA nucleotides fill in the empty spaces along the side of DNA.

– mRNA is made, leaves the nucleus to go to ribosome.

Steps in Protein Synthesis: TranslationLocation: in the cytoplasm, on the ribosome.Purpose: to convert the instructions of RNA (order of bases) into amino

acids, this will make up the protein.Events of translation:1. The first three bases of mRNA (codon) join the ribosome. Usually (AUG

– considered the start codon).2. tRNA brings the “amino acid” down to the ribosome. The three bases

on tRNA (anticodon) match the complementary bases on mRNA.3. Each tRNA has an amino acid, which is determined by the anticodon.

Ex: mRNA codon (AUG) tRNA anticodon (UAC)Amino Acid – (methionine)

4. The amino acids are joined by polypeptide bonds.5. The resulting chain of amino acids are called a protein.

Codons & Anticodons

• Start codon: AUG; codes for the amino acid methionine & starts protein synthesis

• Stop codon: UAG, UAA, UGA; stops protein synthesis

• ANTICODON - segment of three bases on tRNA that is complementary to the mRNA codon.

(Add to the blank space) Proteins

• There are 64 combinations of 3-bases of mRNA called mRNA triplets

• There are 20 different amino acids that form to make proteins

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